Search NASA⌕ Search

SEARCH · Search NASA

Results for “Hg(OF)2”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Removable, Sequestration Coatings for Mitigating Hazardous Contaminants Related to Deactivation and Decommissioning Activities

This project is a collaborative effort between InnoSense LLC (ISL) and Oak Ridge National Laboratory (ORNL) aimed at mitigating the mercury (Hg) contamination problem at the Y-12 National Security Complex (NSC). The report summarizes the research and technology development work of the Phase IIB Project, led by Dr. Uma Sampathkumaran at ISL for the period of July 31, 2017–October 31, 2021. The Y-12 site cleanup includes technologies for safe and cost-effective facility demolition, soil remediation, and on-site treatment and disposal of mercury bearing wastes. One of the technology demonstration goals was a reactive strippable coating for targeted pre-demolition and de-contamination to limit Hg mobilization and the volume of debris requiring treatment for disposal. Toward this, ISL has developed a water-based reactive strippable coating (Trap & See-Hg™) to sequester elemental Hg(0) and mercuric Hg(II) species in the coating. The coating provides multiple benefits including (1) Hg vapor suppression, (2) sealing in the hazardous contaminants, (3) visually locating the contaminant through color changes, and (4) remediating the contaminated surfaces upon coating removal. Through collaboration between ORNL and ISL in Phase II work, the team successfully demonstrated the Trap & See-Hg technology to (1) visually locate the presence of Hg on concrete, soil and drywall surfaces, (2) effectively sequester all mercury species (elemental, soluble and insoluble Hg) from lab-generated and ex-situ soil and brick/rubble samples collected from the Y 12 site with 80 to 95% efficiency to capture/reduce Hg vapor concentration, (3) be applied by manual and robotic spray applicators and cure at room ambient, (4) remain a cohesive and peelable coating upon drying, and (5) sequester Hg0 from walls in the alpha-2 building basement at Y-12 during a small scale in-situ field trial. In Phase IIB, ISL’s effort was focused on refining the coating formulations with additives containing passive and reactive sorbents, colorimetric indicator, and thixotropic agents to achieve the desired performance. The paints were then evaluated at ORNL for applicability to metal and concrete surfaces of different sizes and shapes, and soil rubble, Hg-sorption capacity and achieving sag-free coating on surfaces when applied by a manual spray applicator. Ambient cure of the coating resulted in a dry thickness of 16–20 mil. The coatings were removed from smooth or rough surfaces with low to moderate force. Both lab-generated Hg-contaminated samples and soil and brick/rubble samples containing a range of Hg concentrations (collected from the Y-12 site by UCOR) were used in this project. Optimized formulations were applied to these samples and evaluated for ability to suppress Hg vapors, sequester Hg 0 and Hg(II) species and color mapping of mercury species on the test surface. The ORNL team initially identified three to four potential sites at Y-12 and ORNL for potential demonstration. However, the pandemic closed any possible avenues for on-site demonstration of the robotic spray applicator. The metal and concrete samples with low to high Hg content provided by UCOR from an ongoing demolition were subsequently used for ex-situ sample characterization and analysis at ORNL over a period of 25 days. The coatings suppressed Hg vapors with an efficiency of 95–99% from heavily contaminated metal and 60% from concrete substrate. Analysis of total Hg in the peeled paints indicates sorption capacities ranging from 12 µg Hg/g of paint from concrete to 1.2 mg Hg/g of paint from the metal substrates while peeled paints from soil samples could capture a total Hg from 2.3 mg Hg/g to 66 mg/g paint. Toxicity characteristic leaching procedure (TCLP) tests recovered total mercury leached at 0.15±0.0008 µg/L for concrete to 126.81±0.67 µg/L and 377.25±5.67 µg/L for the two metal substrates, to allow for informed decisions on downstream disposal considerations. Together, this Phase IIB demonstrated the potential value of the Trap & See-Hg for Hg uptake, vapor suppression, and color mapping, and may thus be used to enhance worker safety during site cleanup, facility demolition, and downstream waste disposal at Y-12 NSC.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Sr11Hg54 by Materials Project

Sr11Hg54 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded in a 1-coordinate geometry to thirteen Hg atoms. There are a spread of Sr–Hg bond distances ranging from 3.32–3.74 Å. In the second Sr site, Sr is bonded in a 9-coordinate geometry to nine Hg atoms. There are a spread of Sr–Hg bond distances ranging from 3.26–3.52 Å. In the third Sr site, Sr is bonded in a 1-coordinate geometry to fourteen Hg atoms. There are a spread of Sr–Hg bond distances ranging from 3.34–3.71 Å. In the fourth Sr site, Sr is bonded in a 1-coordinate geometry to fifteen Hg atoms. There are a spread of Sr–Hg bond distances ranging from 3.46–3.76 Å. There are fourteen inequivalent Hg sites. In the first Hg site, Hg is bonded in a 9-coordinate geometry to three equivalent Sr and six equivalent Hg atoms. All Hg–Hg bond lengths are 3.11 Å. In the second Hg site, Hg is bonded in a 1-coordinate geometry to three Sr and three Hg atoms. There are a spread of Hg–Hg bond distances ranging from 2.98–3.29 Å. In the third Hg site, Hg is bonded in a 2-coordinate geometry to two Sr and three Hg atoms. There are a spread of Hg–Hg bond distances ranging from 3.18–3.28 Å. In the fourth Hg site, Hg is bonded in a 9-coordinate geometry to three Sr and six Hg atoms. There are a spread of Hg–Hg bond distances ranging from 3.02–3.36 Å. In the fifth Hg site, Hg is bonded in a 10-coordinate geometry to three equivalent Sr and seven Hg atoms. The Hg–Hg bond length is 3.26 Å. In the sixth Hg site, Hg is bonded in a 7-coordinate geometry to three Sr and four Hg atoms. There are a spread of Hg–Hg bond distances ranging from 2.95–3.19 Å. In the seventh Hg site, Hg is bonded in a 1-coordinate geometry to one Sr and three Hg atoms. There are one shorter (3.09 Å) and two longer (3.35 Å) Hg–Hg bond lengths. In the eighth Hg site, Hg is bonded in a 2-coordinate geometry to two Sr and two equivalent Hg atoms. Both Hg–Hg bond lengths are 3.15 Å. In the ninth Hg site, Hg is bonded in a distorted hexagonal planar geometry to three equivalent Sr and three equivalent Hg atoms. All Hg–Hg bond lengths are 3.04 Å. In the tenth Hg site, Hg is bonded in a 1-coordinate geometry to one Sr and two equivalent Hg atoms. In the eleventh Hg site, Hg is bonded in a 8-coordinate geometry to four Sr and four Hg atoms. There are one shorter (3.04 Å) and one longer (3.15 Å) Hg–Hg bond lengths. In the twelfth Hg site, Hg is bonded in a 9-coordinate geometry to nine Hg atoms. In the thirteenth Hg site, Hg is bonded in a 9-coordinate geometry to three Sr and four Hg atoms. The Hg–Hg bond length is 3.18 Å. In the fourteenth Hg site, Hg is bonded in a 10-coordinate geometry to three Sr and seven Hg atoms.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Impact of the ISS Environment on CNS in Drosophila Melanogaster

Altered gravity and elevated carbon dioxide (CO 2 ) levels as experienced on the ISS can adversely affect human health across various organ systems, especially the Central Nervous System (CNS). Investigating these changes is essential for understanding the long-term effects of spaceflight on human physiology to ensure crew health. Ground-based analogs provide an efficient method to evaluate alterations induced by chronic spaceflight on a larger scale. This study focuses on CNS changes in response to hypergravity (HG) and elevated CO 2 levels via a ground-based analog using the well-established model organism, Drosophila melanogaster. We hypothesize behavior and physiological changes immediately post exposure to HG+CO 2 , along with chronic effects up to 25 days post-exposure. Adult male and female flies were exposed to varying gravity loads (1g, 1.2g, and 3g) and elevated CO 2 levels (~4000 ppm, mimicking CO 2 levels on the ISS) for 15 days and were assessed immediately and at 5-, 10-, and 25-days post-exposure, mirroring astronauts’ post-return profiling. The flies were assessed for neurobehavioral changes, including longevity and negative geotaxis; brain morphological changes, such as dopaminergic neuron count, apoptosis, and glial cell density; and bioenergetic changes in the brain, including mitochondrial abundance and membrane potential. Longevity remained unchanged under hypergravity, even with the addition of elevated CO 2 as a stressor. However, despite the stable lifespan, quality of life appeared to be affected, as shown by negative geotaxis and neuroanatomical changes. Negative geotaxis testing revealed a reduction in motor ability at R0 across all conditions, which correlated with a decrease in dopaminergic (DA) neuron count. Additional observations suggested further systemic alterations, including a decrease in glial cell count, an increase in apoptosis, and notable bioenergetic changes. Collectively, these findings contribute to our understanding of the long-term effects of spaceflight on the CNS.

spaceflight↗
NASA NTRS1977

Time-resolved double-probe study in a He-Hg afterglow plasma

An experimental double-probe technique is described which allows the He(+) ion density to be measured directly as a function of time in the afterglow of a helium-metal-vapor discharge. As an application example, two CW laser transitions of the He-Hg(+) laser at 6150 and 7944 A are considered which both arise from excited 7p (2) P terms of Hg II. The time-resolved double-probe technique is used to measure the destruction rate of the He(+) ion density, which is then compared with the spontaneous-emission decay rate for 7p (2) P terms of Hg II. The results obtained show unambiguously and directly that the dominant excitation process for the two transitions considered is a charge-transfer collisional reaction of the form He(+) plus Hg yields He plus metastable Hg(+) plus the energy defect for this reaction. It is noted that the time-resolved double-probe technique may provide a simple method for measuring ion mobilities in a multi-ion plasma.

Shay, T.↗
DOE OSTI2024

Reduction of Hg II by Mn II

The reduction of Hg II to Hg I or Hg 0 can lead to significant changes in Hg toxicity and mobility in the environment. Photochemical reduction is the primary process for the reduction of Hg II to Hg 0 in sunlit environments; however, dark reduction of HgII can occur via microbial metabolic processes and/or reduction by reduced natural organic matter, Fe II mineral phases, Fe II sorbed to minerals, or aqueous Fe II . Here, in this study, we demonstrate a novel Hg II reduction pathway involving another environmentally relevant reductant, Mn II . Abiotic reduction of Hg II O by Mn II was studied as a function of pH and anion environment (perchlorate, sulfate, chloride) using X-ray absorption spectroscopy to characterize the solid-phase Hg and Mn species. At circumneutral pH of 7.5, about 70% of Hg II was reduced to elemental Hg 0 within 2 h. In contrast, 12 h were needed to achieve the same extent of reduction at pH 6.9. In the presence of sulfate and chloride, Hg I species were formed. Hg II reduction was initially rapid and coupled with the oxidation of soluble Mn II -oxides to insoluble Mn IV -oxides, followed by a significantly slower reduction of Hg II during the Mn II -catalyzed transformation of the Mn IV -oxides to hydroxide and oxyhydroxide minerals. The observed reduction of Hg II by Mn II at circumneutral pH could be an important transformation pathway for environmental Hg, affecting its bioavailability and mobility under mildly reducing conditions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

1,3-Dimethyl-2,3-dihydrobenzo[ d ]imidazoles, 1H , and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[ d ]imidazoles, 1 2 , are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[ d ]imidazolium ( 1g–i + , respectively) have been synthesized and reduced with NaBH 4 to 1gH , 1hH , and 1iH , and with Na:Hg to 1g 2 and 1h 2 . Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- ( 1b + ) and 2-cyclohexylbenzo[ d ]imidazolium ( 1e + ) salts. E ( 1 + / 1 • ) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducing E ( 1 + / 1 • ) values, as well as cathodic shifts in E ( 1 2 •+ / 1 2 ) and E ( 1H •+ / 1H ) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the 1H species with PC 61 BM. Because 2-aryl groups stabilize radicals, 1b 2 and 1g 2 exhibit weaker bonds than 1e 2 and 1h 2 and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene ( VII ) via a “cleavage-first” pathway, while 1e 2 and 1h 2 react only via “electron-transfer-first”. 1h 2 exhibits the most cathodic E ( 1 2 •+ / 1 2 ) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers with VII via “electron-transfer-first”. Crystal structures show rather long central C–C bonds for 1b 2 (1.5899(11) and 1.6194(8) Å) and 1h 2 (1.6299(13) Å).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Hg8Br3O4 by Materials Project

HgBrHg7(O2Br)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two HgBr ribbons oriented in the (0, 1, 0) direction and two Hg7(O2Br)2 sheets oriented in the (0, 0, 1) direction. In each HgBr ribbon, Hg+1.38+ is bonded in a 2-coordinate geometry to one Hg+1.38+ and two equivalent Br1- atoms. The Hg–Hg bond length is 2.64 Å. There are one shorter (2.58 Å) and one longer (3.01 Å) Hg–Br bond lengths. Br1- is bonded in an L-shaped geometry to two equivalent Hg+1.38+ atoms. In each Hg7(O2Br)2 sheet, there are seven inequivalent Hg+1.38+ sites. In the first Hg+1.38+ site, Hg+1.38+ is bonded in a distorted see-saw-like geometry to two O2- and two Br1- atoms. There are one shorter (2.18 Å) and one longer (2.39 Å) Hg–O bond lengths. There are one shorter (2.66 Å) and one longer (2.90 Å) Hg–Br bond lengths. In the second Hg+1.38+ site, Hg+1.38+ is bonded in a 4-coordinate geometry to three O2- and one Br1- atom. There are a spread of Hg–O bond distances ranging from 2.18–2.52 Å. The Hg–Br bond length is 2.88 Å. In the third Hg+1.38+ site, Hg+1.38+ is bonded in an L-shaped geometry to two O2- atoms. There are one shorter (2.39 Å) and one longer (2.41 Å) Hg–O bond lengths. In the fourth Hg+1.38+ site, Hg+1.38+ is bonded in a 1-coordinate geometry to three O2- and one Br1- atom. There are a spread of Hg–O bond distances ranging from 2.54–2.92 Å. The Hg–Br bond length is 3.48 Å. In the fifth Hg+1.38+ site, Hg+1.38+ is bonded in a distorted linear geometry to two O2- and one Br1- atom. There are one shorter (2.03 Å) and one longer (2.08 Å) Hg–O bond lengths. The Hg–Br bond length is 3.13 Å. In the sixth Hg+1.38+ site, Hg+1.38+ is bonded in a distorted single-bond geometry to one O2- and three Br1- atoms. The Hg–O bond length is 2.20 Å. There are a spread of Hg–Br bond distances ranging from 3.25–3.33 Å. In the seventh Hg+1.38+ site, Hg+1.38+ is bonded in a trigonal planar geometry to three O2- and one Br1- atom. There are a spread of Hg–O bond distances ranging from 2.22–2.29 Å. The Hg–Br bond length is 3.30 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to four Hg+1.38+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to four Hg+1.38+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Hg+1.38+ atoms. In the fourth O2- site, O2- is bonded to four Hg+1.38+ atoms to form distorted corner-sharing OHg4 tetrahedra. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 1-coordinate geometry to four Hg+1.38+ atoms. In the second Br1- site, Br1- is bonded in a 2-coordinate geometry to five Hg+1.38+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ancient Origin of Acetyltransferases Catalyzing O -acetylation of Plant Cell Wall Polysaccharides

Abstract Members of the domain of unknown function 231/trichome birefringence–like (TBL) family have been shown to be O-acetyltransferases catalyzing the acetylation of plant cell wall polysaccharides, including pectins, mannan, xyloglucan and xylan. However, little is known about the origin and evolution of plant cell wall polysaccharide acetyltransferases. Here, we investigated the biochemical functions of TBL homologs from Klebsormidium nitens, a representative of an early divergent class of charophyte green algae that are considered to be the closest living relatives of land plants, and Marchantia polymorpha, a liverwort that is an extant representative of an ancient lineage of land plants. The genomes of K. nitens and Marchantia polymorpha harbor two and six TBL homologs, respectively. Biochemical characterization of their recombinant proteins expressed in human embryonic kidney 293 cells demonstrated that the two K. nitens TBLs exhibited acetyltransferase activities acetylating the pectin homogalacturonan (HG) and hence were named KnPOAT1 and KnPOAT2. Among the six M. polymorpha TBLs, five (MpPOAT1 to 5) possessed acetyltransferase activities toward pectins and the remaining one (MpMOAT1) catalyzed 2-O- and 3-O-acetylation of mannan. While MpPOAT1,2 specifically acetylated HG, MpPOAT3,4,5 could acetylate both HG and rhamnogalacturonan-I. Consistent with the acetyltransferase activities of these TBLs, pectins isolated from K. nitens and both pectins and mannan from M. polymorpha were shown to be acetylated. These findings indicate that the TBL genes were recruited as cell wall polysaccharide O-acetyltransferases as early as in charophyte green algae with activities toward pectins and they underwent expansion and functional diversification to acetylate various cell wall polysaccharides during evolution of land plants.

Cell Biology↗
DOE OSTI2020

Materials Data on Hg3Pb by Materials Project

Hg3Pb crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hg is bonded in a 2-coordinate geometry to six equivalent Hg and four equivalent Pb atoms. There are four shorter (3.29 Å) and two longer (3.37 Å) Hg–Hg bond lengths. There are two shorter (3.35 Å) and two longer (3.46 Å) Hg–Pb bond lengths. Pb is bonded to twelve equivalent Hg atoms to form a mixture of corner and face-sharing PbHg12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Toggling Stereochemical Activity through Interstitial Positioning of Cations between 2D V 2 O 5 Double Layers

The 5/6s 2 lone-pair electrons of p-block cations in their lower oxidation states are a versatile electronic and geometric structure motif that can underpin lattice anharmonicity and often engender electronic and structural instabilities that underpin the function of active elements in nonlinear optics, thermochromics, thermoelectrics, neuromorphic computing, and photocatalysis. In contrast to periodic solids where lone-pair-bearing cations are part of the structural framework, installing lone-pair-bearing cations in the interstitial sites of intercalation hosts provides a means of a systematically modulating electronic structure through the choice of the group and the period of the inserted cation while preserving the overall framework connectivity. The extent of stereochemical activity and the energy positioning of lone-pair-derived mid-gap states depend on the cation identity, stoichiometry, and strength of anion hybridization. V 2 O 5 polymorphs are versatile insertion hosts that can accommodate a broad range of s-, p-, and d-block cations. However, the insertion of lone-pair-bearing cations remains largely underexplored. In this article, we examine the implications of varying the 6s 2 cations situated in interlayer sites between condensed [V 4 O 10 ] n double layers. Systematic modulations of lattice distortions, electronic structure, and magnetic ordering are observed with increasing strength of stereochemical activity from group 12 to group 14 cations. We compare and contrast p-block-layered M x V 2 O 5 (M = Hg, Tl, and Pb) compounds and map the significance of local off-centering arising from the stereochemical activity of lone-pair cations to the emergence of filled antibonding lone-pair 6s 2 –O 2p-hybridized mid-gap states mediated by second-order Jahn–Teller distortions. Crystallographic studies of cation coordination environments and the resulting modulation of V–V interactions have been used in conjunction with variable-energy hard X-ray photoelectron spectroscopy measurements, first-principles electronic structure calculations, and crystal orbital Hamilton population analyses to decipher the origins of stereochemical activity. Magnetic susceptibility measurements reveal antiferromagnetic signatures for all the three compounds. However, the differences in V–V interactions significantly affect the energy balance of the superexchange interactions, resulting in an ordering temperature of 160 and 260 K for Hg 0.5 V 2 O 5 and δ-Tl 0.5 V 2 O 5 , respectively, as compared to 7 K for δ-Pb 0.5 V 2 O 5 . In δ-Pb 0.5 V 2 O 5 , the strong stereochemical activity of electron lone pairs and the resulting electrostatic repulsions enforce superlattice ordering, which strongly modifies the electronic localization patterns along the [V 4 O 10 ] slabs, resulting in disrupted magnetic ordering and an anomalously low ordering temperature. The results demonstrate a versatile strategy for toggling the stereochemical activity of electron lone pairs to modify the electronic structure near the Fermi level and to mediate superexchange interactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Hg11I2BrClO4 by Materials Project

Hg11O4I2BrCl crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eleven inequivalent Hg+1.09+ sites. In the first Hg+1.09+ site, Hg+1.09+ is bonded in a distorted L-shaped geometry to two O2-, two I1-, and one Br1- atom. There are one shorter (2.22 Å) and one longer (2.77 Å) Hg–O bond lengths. There are one shorter (3.55 Å) and one longer (3.79 Å) Hg–I bond lengths. The Hg–Br bond length is 3.48 Å. In the second Hg+1.09+ site, Hg+1.09+ is bonded in a distorted L-shaped geometry to two O2-, two I1-, and one Cl1- atom. There are one shorter (2.21 Å) and one longer (2.76 Å) Hg–O bond lengths. There are one shorter (3.57 Å) and one longer (3.78 Å) Hg–I bond lengths. The Hg–Cl bond length is 3.44 Å. In the third Hg+1.09+ site, Hg+1.09+ is bonded in a distorted single-bond geometry to one O2-, one I1-, and one Br1- atom. The Hg–O bond length is 2.19 Å. The Hg–I bond length is 3.33 Å. The Hg–Br bond length is 3.07 Å. In the fourth Hg+1.09+ site, Hg+1.09+ is bonded in a distorted single-bond geometry to one O2-, one I1-, and one Cl1- atom. The Hg–O bond length is 2.18 Å. The Hg–I bond length is 3.37 Å. The Hg–Cl bond length is 2.98 Å. In the fifth Hg+1.09+ site, Hg+1.09+ is bonded in a distorted L-shaped geometry to two O2-, one Br1-, and one Cl1- atom. There are one shorter (2.23 Å) and one longer (2.61 Å) Hg–O bond lengths. The Hg–Br bond length is 3.68 Å. The Hg–Cl bond length is 3.21 Å. In the sixth Hg+1.09+ site, Hg+1.09+ is bonded in a distorted L-shaped geometry to two O2- and one Br1- atom. There are one shorter (2.23 Å) and one longer (2.62 Å) Hg–O bond lengths. The Hg–Br bond length is 3.30 Å. In the seventh Hg+1.09+ site, Hg+1.09+ is bonded in a linear geometry to two O2-, two I1-, and one Br1- atom. Both Hg–O bond lengths are 2.08 Å. There are one shorter (3.34 Å) and one longer (3.35 Å) Hg–I bond lengths. The Hg–Br bond length is 3.66 Å. In the eighth Hg+1.09+ site, Hg+1.09+ is bonded in a distorted single-bond geometry to one O2-, one Br1-, and one Cl1- atom. The Hg–O bond length is 2.18 Å. The Hg–Br bond length is 3.61 Å. The Hg–Cl bond length is 3.09 Å. In the ninth Hg+1.09+ site, Hg+1.09+ is bonded in a distorted single-bond geometry to one O2- and one Br1- atom. The Hg–O bond length is 2.20 Å. The Hg–Br bond length is 3.14 Å. In the tenth Hg+1.09+ site, Hg+1.09+ is bonded in a single-bond geometry to one O2-, three I1-, and one Cl1- atom. The Hg–O bond length is 2.22 Å. There are a spread of Hg–I bond distances ranging from 3.44–3.59 Å. The Hg–Cl bond length is 3.41 Å. In the eleventh Hg+1.09+ site, Hg+1.09+ is bonded in a single-bond geometry to one O2-, three I1-, and one Br1- atom. The Hg–O bond length is 2.22 Å. There are a spread of Hg–I bond distances ranging from 3.44–3.57 Å. The Hg–Br bond length is 3.40 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Hg+1.09+ atoms to form distorted edge-sharing OHg4 tetrahedra. In the second O2- site, O2- is bonded to four Hg+1.09+ and one Br1- atom to form distorted edge-sharing OHg4Br tetrahedra. The O–Br bond length is 3.36 Å. In the third O2- site, O2- is bonded to four Hg+1.09+ and one I1- atom to form a mixture of distorted edge and corner-sharing OHg4I tetrahedra. The O–I bond length is 3.56 Å. In the fourth O2- site, O2- is bonded to four Hg+1.09+ and one I1- atom to form a mixture of distorted edge and corner-sharing OHg4I tetrahedra. The O–I bond length is 3.57 Å. There are two inequivalent I1- sites. In the first I1- site, I1- is bonded in a 8-coordinate geometry to seven Hg+1.09+ and one O2- atom. In the second I1- site, I1- is bonded in a 6-coordinate geometry to seven Hg+1.09+ and one O2- atom. Br1- is bonded in a 2-coordinate geometry to eight Hg+1.09+ and one O2- atom. Cl1- is bonded in a 2-coordinate geometry to five Hg+1.09+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Mercury Removal from Contaminated Water by Wood-Based Biochar Depends on Natural Organic Matter and Ionic Composition

Biochars can remove potentially toxic elements, such as inorganic mercury [Hg(II)] from contaminated waters. However, their performance in complex water matrices is rarely investigated, and the combined roles of natural organic matter (NOM) and ionic composition in the removal of Hg(II) by biochar remain unclear. Here, we investigate the influence of NOM and major ions such as chloride (Cl – ), nitrate (NO 3 – ), calcium (Ca 2+ ), and sodium (Na + ) on Hg(II) removal by a wood-based biochar (SWP700). Multiple sorption sites containing sulfur (S) were located within the porous SWP700. In the absence of NOM, Hg(II) removal was driven by these sites. Ca 2+ bridging was important in enhancing removal of negatively charged Hg(II)-chloro complexes. In the presence of NOM, formation of soluble Hg-NOM complexes (as seen from speciation calculations), which have limited access to biochar pores, suppressed Hg(II) removal, but Cl – and Ca 2+ could still facilitate it. The ability of Ca 2+ to aggregate NOM, including Hg-NOM complexes, promoted Hg(II) removal from the dissolved fraction (<0.45 μm). Hg(II) removal in the presence of Cl – followed a stepwise mechanism. Weakly bound oxygen functional groups in NOM were outcompeted by Cl – , forming smaller-sized Hg(II)-chloro complexes, which could access additional intraparticle sorption sites. Therein, Cl – was outcompeted by S, which finally immobilized Hg(II) in SWP700 as confirmed by extended X-ray absorption fine structure spectroscopy. We conclude that in NOM containing oxic waters, with relatively high molar ratios of Cl – : NOM and Ca 2+ : NOM, Hg(II) removal can still be effective with SWP700.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Materials Data on Hg15(As2Cl3)4 by Materials Project

Hg(Hg7(As2Cl3)2)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of two mercury molecules and one Hg7(As2Cl3)2 framework. In the Hg7(As2Cl3)2 framework, there are eight inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded to six Cl1- atoms to form edge-sharing HgCl6 octahedra. There are two shorter (2.75 Å) and four longer (2.76 Å) Hg–Cl bond lengths. In the second Hg2+ site, Hg2+ is bonded to six Cl1- atoms to form edge-sharing HgCl6 octahedra. All Hg–Cl bond lengths are 2.76 Å. In the third Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, and edges with six HgCl6 octahedra. The corner-sharing octahedra tilt angles range from 16–88°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.01–3.40 Å. In the fourth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, and edges with six HgCl6 octahedra. The corner-sharing octahedra tilt angles range from 16–88°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.01–3.41 Å. In the fifth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, and edges with six HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 16–88°. Both Hg–As bond lengths are 2.57 Å. There are a spread of Hg–Cl bond distances ranging from 3.01–3.41 Å. In the sixth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, and edges with six HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 16–88°. Both Hg–As bond lengths are 2.56 Å. There are a spread of Hg–Cl bond distances ranging from 3.01–3.40 Å. In the seventh Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, and edges with six HgCl6 octahedra. The corner-sharing octahedra tilt angles range from 16–88°. Both Hg–As bond lengths are 2.57 Å. There are a spread of Hg–Cl bond distances ranging from 3.01–3.41 Å. In the eighth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, and edges with six HgCl6 octahedra. The corner-sharing octahedra tilt angles range from 16–88°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.01–3.40 Å. There are four inequivalent As+2.25- sites. In the first As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra, corners with four ClHg5 square pyramids, and corners with three AsHg3As tetrahedra. The corner-sharing octahedral tilt angles are 70°. The As–As bond length is 2.51 Å. In the second As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra, corners with two ClHg5 square pyramids, corners with three AsHg3As tetrahedra, and an edgeedge with one ClHg5 square pyramid. The corner-sharing octahedral tilt angles are 74°. The As–As bond length is 2.51 Å. In the third As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra, corners with four ClHg5 square pyramids, corners with three AsHg3As tetrahedra, and edges with two ClHg5 square pyramids. The corner-sharing octahedral tilt angles are 74°. In the fourth As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra, corners with two ClHg5 square pyramids, corners with three AsHg3As tetrahedra, and edges with three ClHg5 square pyramids. The corner-sharing octahedral tilt angles are 70°. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Hg2+ atoms. In the second Cl1- site, Cl1- is bonded to five Hg2+ atoms to form distorted ClHg5 square pyramids that share corners with five ClHg5 square pyramids, corners with four AsHg3As tetrahedra, and edges with two AsHg3As tetrahedra. In the third Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Hg2+ atoms. In the fourth Cl1- site, Cl1- is bonded to five Hg2+ atoms to form distorted ClHg5 square pyramids that share corners with seven ClHg5 square pyramids, corners with four AsHg3As tetrahedra, edges with two equivalent ClHg5 square pyramids, and edges with two AsHg3As tetrahedra. In the fifth Cl1- site, Cl1- is bonded to five Hg2+ atoms to form distorted ClHg5 square pyramids that share corners with seven ClHg5 square pyramids, corners with four AsHg3As tetrahedra, edges with two equivalent ClHg5 square pyramids, and edges with two AsHg3As tetrahedra. In the sixth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to five Hg2+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2004

Evaluation of the Paratrend Multi-Analyte Sensor for Potential Utilization in Long-Duration Automated Cell Culture Monitoring

BACKGROUND: Compact and automated sensors are desired for assessing the health of cell cultures in biotechnology experiments. While several single-analyte sensors exist to measure culture health, a multi-analyte sensor would simplify the cell culture system. One such multi-analyte sensor, the Paratrend 7 manufactured by Diametrics Medical, consists of three optical fibers for measuring pH, dissolved carbon dioxide (pCO(2)), dissolved oxygen (pO(2)), and a thermocouple to measure temperature. The sensor bundle was designed for intra-vascular measurements in clinical settings, and can be used in bioreactors operated both on the ground and in NASA's Space Shuttle and International Space Station (ISS) experiments. METHODS: A Paratrend 7 sensor was placed at the outlet of a bioreactor inoculated with BHK-21 (baby hamster kidney) cells. The pH, pCO(2), pO(2), and temperature data were transferred continuously to an external computer. Cell culture medium, manually extracted from the bioreactor through a sampling port, was also assayed using a bench top blood gas analyzer (BGA). RESULTS: Two Paratrend 7 sensors were used over a single cell culture experiment (64 days). When compared to the manually obtained BGA samples, the sensor had good agreement for pH, pCO(2), and pO(2) with bias (and precision) 0.005(0.024), 8.0 mmHg (4.4 mmHg), and 11 mmHg (17 mmHg), respectively for the first two sensors. A third Paratrend sensor (operated for 141 days) had similar agreement (0.02+/-0.15 for pH, -4+/-8 mm Hg for pCO(2), and 24+/-18 mmHg for pO(2)). CONCLUSION: The resulting biases and precisions are com- parable to Paratrend sensor clinical results. Although the pO(2) differences may be acceptable for clinically relevant measurement ranges, the O(2) sensor in this bundle may not be reliable enough for the ranges of pO(2) in these cell culture studies without periodic calibration.

Validation Studies↗
DOE OSTI2022

Mercury and Radiocesium Accumulation and Associations With Sublethal Endpoints in the Florida Green Watersnake ( Nerodia floridana )

Mercury (Hg) and radiocesium ( 137 Cs) are well-known environmental contaminants with the potential to impact the health of humans and wildlife. Snakes have several characteristics conducive to studying environmental contamination but have rarely been included in the monitoring of polluted sites. We investigated the bioaccumulation of Hg and 137 Cs and associations with sublethal effects (standard metabolic rate [SMR] and hemoparasite infections) in Florida green watersnakes (Nerodia floridana). We captured 78 snakes from three former nuclear cooling reservoirs on the US Department of Energy's Savannah River Site in South Carolina (USA). For captured snakes, we (1) determined whole-body 137 Cs, (2) quantified total Hg (THg) using snake tail clips, (3) conducted hemoparasite counts, and (4) measured the SMR. We used multiple regression models to determine associations among snake body size, capture location, sex, tail THg, whole-body 137 Cs, Hepatozoon spp. prevalence and parasitemia, and SMR. Average whole-body 137 Cs (0.23 ± 0.08 Becquerels [Bq]/g; range: 0.00–1.02 Bq/g) was correlated with snake body size and differed significantly by capture site (Pond B: 0.67 ± 0.05 Bq/g; Par Pond: 0.10 ± 0.02 Bq/g; Pond 2: 0.03 ± 0.02 Bq/g). Tail THg (0.33 ± 0.03 mg/kg dry wt; range: 0.16–2.10 mg/kg) was significantly correlated with snake body size but did not differ by capture site. We found no clear relationship between SMR and contaminant burdens. However, models indicated that the prevalence of Hepatozoon spp. in snakes was inversely related to increasing whole-body 137 Cs burdens. Our results indicate the bioaccumulation of Hg and 137 Cs in N. floridana and further demonstrate the utility of aquatic snakes as bioindicators. Furthermore, our results also suggest a decrease in Hepatozoon spp. prevalence related to increased burdens of 137 Cs. Although the results are intriguing, further research is needed to understand the dynamics between 137 Cs and Hepatozoon spp. infections in semiaquatic snakes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Cryogenic Carbon Capture™ Technoeconomic Analysis

The Cryogenic Carbon Capture™ (CCC) process significantly decreases cost and energy demands for CO 2 separation and pressurization to 150 bar compared to alternatives. The process is a post-combustion technology that cools CO 2 -laden flue gas to desublimation temperatures (-100 to -135 °C), separates solid CO 2 —that forms from the flue gas—from the light gases, uses the cold products to cool incoming gases in a recuperative heat exchanger, compresses the solid/liquid CO 2 to final pressures (100–200 bar), and delivers a compressed CO 2 stream separated from an atmospheric pressure light-gas stream. The overall energy and economic costs are about 30-50% lower than most competing processes that involve air separation units (ASUs), solvents, or similar technologies. In addition, the CCC process enjoys several ancillary benefits, including (a) it is a minimally invasive Bolton technology, (b) it provides highly efficient removal of most pollutants (Hg, SOx, NO 2 , HCl, etc.), and (c) possible energy storage capacity. This report outlines the process details and economic and energy comparisons relative to other well-documented alternatives. This paper presents the results of a detailed techno-economic comparison of CCC with amine-based systems. The comparison uses identical financial and economic assumptions similar process assumptions as the detailed analyses published by US DOE in the greenfield analysis. Specifically, the comparison assumes power plants that produce the same net output, one equipped with and a second without carbon capture. Separately, the paper compares similar analyses for retrofitting existing systems using typical plant characteristics in the US (initial capital costs have been paid, high plant utilization), though there are no DOE estimates available for direct comparison. Financial and technical assumptions for all comparisons are maintained as close to the DOE reference studies as possible. The results demonstrate about 30-50% lower costs and energy demands for capture from greenfield coal plants. Natural gas plants produce substantially lower CO 2 concentrations which makes the cost of capturing a ton of CO 2 at the same capture rate as the coal plant higher for all processes while the cost of CO 2 capture per unit of power generation is lower. However, CCC maintains about the same absolute energy and cost advantages for NG as for coal compared to amine systems. Finally, the costs of retrofitting a station are compared to those of building a new station with and without capture. The retrofit costs are comparable to (slightly lower than) new plant costs without capture. In all cases operating and capital cost comparisons show that the CCC process can be retrofitted to a variety of plants to cost effectively reduce CO 2 emissions. Further process integration into the upstream processes and unique process features like water recovery, and integrated energy storage bring the effective cost of carbon capture using the CCC process down further and increase its advantages over alternatives. This technoeconomic analysis shows that the CCC process has the potential to the be lowest cost carbon capture technology under development today.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2020

Materials Data on Cd2Hg13(As2Cl3)4 by Materials Project

Hg(Hg6Cd(As2Cl3)2)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of two mercury molecules and one Hg6Cd(As2Cl3)2 framework. In the Hg6Cd(As2Cl3)2 framework, there are six inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, edges with two CdCl6 octahedra, and edges with four HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 18–89°. Both Hg–As bond lengths are 2.56 Å. There are a spread of Hg–Cl bond distances ranging from 3.03–3.41 Å. In the second Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, edges with two CdCl6 octahedra, and edges with four HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 18–89°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.02–3.40 Å. In the third Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, edges with two equivalent CdCl6 octahedra, and edges with four HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 18–89°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.02–3.41 Å. In the fourth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, edges with two equivalent CdCl6 octahedra, and edges with four HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 18–89°. Both Hg–As bond lengths are 2.56 Å. There are a spread of Hg–Cl bond distances ranging from 3.02–3.41 Å. In the fifth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, edges with two CdCl6 octahedra, and edges with four HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 18–89°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.03–3.40 Å. In the sixth Hg2+ site, Hg2+ is bonded to two As+2.25- and four Cl1- atoms to form distorted HgAs2Cl4 octahedra that share corners with eight HgAs2Cl4 octahedra, corners with two AsHg3As tetrahedra, edges with two CdCl6 octahedra, and edges with four HgAs2Cl4 octahedra. The corner-sharing octahedra tilt angles range from 18–89°. There are one shorter (2.56 Å) and one longer (2.57 Å) Hg–As bond lengths. There are a spread of Hg–Cl bond distances ranging from 3.02–3.41 Å. There are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to six Cl1- atoms to form CdCl6 octahedra that share edges with twelve HgAs2Cl4 octahedra. All Cd–Cl bond lengths are 2.70 Å. In the second Cd2+ site, Cd2+ is bonded to six Cl1- atoms to form CdCl6 octahedra that share edges with twelve HgAs2Cl4 octahedra. There are two shorter (2.69 Å) and four longer (2.70 Å) Cd–Cl bond lengths. There are four inequivalent As+2.25- sites. In the first As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra and corners with three AsHg3As tetrahedra. The corner-sharing octahedral tilt angles are 70°. The As–As bond length is 2.50 Å. In the second As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra and corners with three AsHg3As tetrahedra. The corner-sharing octahedral tilt angles are 74°. The As–As bond length is 2.51 Å. In the third As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra and corners with three AsHg3As tetrahedra. The corner-sharing octahedral tilt angles are 74°. In the fourth As+2.25- site, As+2.25- is bonded to three Hg2+ and one As+2.25- atom to form AsHg3As tetrahedra that share corners with three HgAs2Cl4 octahedra and corners with three AsHg3As tetrahedra. The corner-sharing octahedral tilt angles are 70°. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four Hg2+ and one Cd2+ atom. In the second Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four Hg2+ and one Cd2+ atom. In the third Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four Hg2+ and one Cd2+ atom. In the fourth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four Hg2+ and one Cd2+ atom. In the fifth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four Hg2+ and one Cd2+ atom. In the sixth Cl1- site, Cl1- is bonded in a 5-coordinate geometry to four Hg2+ and one Cd2+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1990

A study of the influence of Hg(6(3)P2) population in a low-pressure discharge on mercury ion emission at 194.2 nm

A low-pressure mercury-argon discharge, similar to the type existing in the mercury lamp for the trapped-ion standard, is probed with a new technique of laser spectroscopy to determine the influence of the Hg(6 3P(sub 2)) population on discharge emission. The discharge is excited with inductively coupled rf power. Variations in the intensity of emission lines in the discharge were examined as lambda = 546.1 nm light from a continuous wave (CW) laser excited the Hg(6 3P(sub 2)) to (7 3S (sub 1)) transition. The spectrum of the discharge viewed in the region of laser irradiation showed increased emission in lambda = 546.1, 435.8, 404.7, 253.7, and 194.2 nm lines. Other lines in Hg I exhibited a decrease in emission. When the discharge was viewed outside the region of laser irradiation, all lines exhibited an increased emission. Based on these results, it is concluded that the dominant mechanism for the excitation of higher lying levels of mercury is the the electron-impact excitation via the 3P(sub 2) level. The depopulation of this metastable is also responsible for the observed increase in the electron temperature when the laser irradiates the discharge. It is also concluded that the 3P(sub 2) metastable level of mercury does not play a significant role in the excitation of the 3P(sub 1/2) level of mercury ion.

Maleki, L.↗