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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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Probing Noncovalent Interaction Strengths of Host-Guest Complexes Using Negative Ion Photoelectron Spectroscopy

Noncovalent interactions (NCIs) are crucial for the formation and stability of host-guest complexes, which have wide-ranging implications across various fields, including biology, chemistry, materials science, pharmaceuticals, and environmental science. However, since NCIs are relatively weak and sensitive to bulk perturbation, direct and accurate measurement of their absolute strength has always been a significant challenge. This concept article aims to demonstrate the gas-phase electrospray ionization (ESI)-negative ion photoelectron spectroscopy (NIPES) as a direct and precise technique to measure the absolute interaction strength, probe nature of NCIs, and reveal the electronic structural information for host-guest complexes. Here, our recent studies in investigating various host-guest complexes that involve various types of NCIs such as anion–π, (di)hydrogen bonding, charge-separated ionic interactions, are overviewed. Finally, a summary and outlook are provided for this field.

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

Negative Ion Formation in Complex Heavy Systems

The project’s primary objective is to gain a fundamental theoretical understanding of the near-threshold electron attachment mechanism in low energy electron elastic scattering from complex heavy systems through the calculation of integral and differential cross sections and extract reliable electron affinities (EAs). The complex angular momentum (CAM), also known as Regge-pole methodology wherein is fully embedded the crucial electron-electron correlations and the core polarization interaction, is used for the investigations. Regge trajectories allow us to probe electron attachment at the fundamental level near threshold, thereby uncovering new manifestations, including the mechanism of nanocatalysis, and determine reliable EAs. Low-energy electron elastic scattering total cross sections (TCSs) for the lanthanide and actinide atoms and the fullerene molecules are calculated. From the TCSs ground, metastable and excited states anionic binding energies (BEs) are extracted and compared with the available measured and/or calculated EAs. Significantly, our calculated ground state anionic BEs correspond to the theoretically challenging to calculate EAs and they are used to assess the reliability of existing EAs. Doubly charged negative ions of atoms and molecules are proposed as novel tunable catalysts and demonstrated in the oxidation of water into peroxide. Negatively charged fullerene molecules are used to catalyze water oxidation to peroxide and water synthesis from H 2 and O 2 as well. Violation of time-reversal and particle-hole symmetries in strongly correlated Fermi systems are reviewed with the collaboration involving the International Laboratory of Fermi Condensation.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1989

Photodetachment cross sections of negative ions - The range of validity of the Wigner threshold law

The threshold behavior of the photodetachment cross section of negative ions as a function of photon frequency is usually described by the Wigner law. This paper reports the results of a model calculation using the zero-core-contribution (ZCC) approximation. Theoretical expressions for the leading correction to the Wigner law are developed, giving the range of validity of the Wigner law and the expected accuracy. The results are relevant to extraction of electron affinities from experimental photodetachment data.

Farley, John W.↗
NASA NTRS1985

A negative ion model in the lower stratosphere

There are a number of problems in the electricity of the stratosphere at middle latitudes; e.g., the positive relation between the seasonal variations of negative polar conductivity and that of ozone density, the observed dependence of the daytime variation of conductivity on the solar zenith angle, and the interaction between the ions and aerosols, particularly the processes of the conversion from negative ions to the sulfate aerosols; e.g., ion-nucleation and the growth through multi-ion complexes. As a basic tool for investigating these problems, a negative ion chemical model was constructed in the altitude region of 15 to 30 km. Recently, the success of in situ mass analysis of stratospheric ions has revealed the nature of the most abundant ions in the stratosphere. Further, the height variations of negative ion composition between 15 and 34 km were obtained with the balloon-borne mass spectrometer by another researcher. A comparison of the calculated result with the observed result is given.

Kawamoto, H.↗
DOE OSTI2023

Quantitative Measurement of Positive and Negative Ion Species Ejected from a Li–O–H Surface by Hydrogen and Noble Gas Ion Irradiation

We report sputtering yields of Li + , H - , O - , and OH x - ion species from an Li–O–H surface for H, D, He, Ne, and Ar ion irradiation at 45° incidence in the energy range of 30–2000 eV. A Li film was deposited on a stainless steel target using Li evaporators in the LTX-β vessel, using the LTX-β Sample Exposure Probe (SEP), which includes an ultrahigh vacuum suitcase for transferring targets without significant contamination from air exposure. The SEP was used to transfer the Li-coated target from LTX-β to a separate Sample Exposure Station (SES) to perform ion exposure measurements. The SEP was also used for characterization of the Li-coated target utilizing X-ray photoelectron spectroscopy in a different chamber, showing that the lithium film surface was oxidized. Ion exposures were performed using an electron cyclotron resonance plasma source in the SES. Sputtered/ejected species were sampled by a quadrupole mass spectrometer with capabilities for detecting positive and negative ions, and an energy filter for determining the mean kinetic energy of the ejected ion species. All ion irradiations caused Li + ions to be ejected, while causing impurity ions such as H + , H - , O - and OH - to be ejected. Measured ion energies of Li + ions from a Li–O–H surface suggested that the typical sheath potential on the divertor surface can trap sputtered Li + ions, which were previously reported as ~ 60% of total sputtered Li species from Li targets (Allain and Ruzic in Nucl Fusion 42:202, 2002). Hence, our results for the sputtering yields of ejected ion species and their associated ion energies from a Li–O–H surface indicates that lithium sputtering is suppressed and impurity removal is enhanced due to the sheath potential at the divertor surface for fusion reactor applications.

Plasma-material interaction↗
NASA NTRS1987

Generation of intense negative ion beams

An electron gun is used with a mirror electrostatic field to produce zero or near zero velocity electrons by forming a turning point in their trajectories. A gas capable of attaching zero or near zero velocity is introduced at this turning point, and negative ions are produced by the attachment or dissociative attachment process. Operation may be continuous or pulsed. Ions thus formed are extracted by a simple lens system and suitable biasing of grids.

Chutjian, Ara↗
NASA NTRS2007

Doubly Excited Resonances in the Positronium Negative Ion

The recent theoretical studies on the doubly excited states of the Ps' ion are described. The results obtained by using the method of complex coordinate rotation show that the three-lepton system behaves very much like an XYX tri-atomic molecule. Furthermore, the recent investigation on the positronium negative ion embedded in Debye plasma environments is discussed. The problem is modeled by the use of a screened Coulomb potential to represent the interaction between the charge particles.

Ho, Y.K.↗
DOE OSTI2025

Gas-phase negative ion photoelectron spectroscopy and reactivity of phenylacetylide

Arylacetylides such as phenylacetylide (PhCC–, 1) are important nucleophiles used in synthetic chemistry yet rarely have they been studied as bare carbanions. In this work, the phenylacetylide anion was formed via electrospray ionization (ESI) or multistage mass spectrometry (MSn) experiments and subsequently examined in the gas phase by negative ion photoelectron spectroscopy (NIPES), ion-molecule reactions (IMR), alongside theoretical calculations to probe its fundamental structure and reactivity. Photoelectron spectra of PhCC– (1) revealed vertical (VDE) and adiabatic detachment energies (ADE), both of 3.220 eV. The latter value is also the electron affinity (EA) of the phenylethynyl radical (PhCC•) from which a bond dissociation energy (BDE) of phenylacetylene (PhCCH) was derived to be ca. 131.3 ± 1.7 kcal mol-1 using a gas-phase thermochemical cycle. Detachment of an electron from PhCC– at 266 nm likely results in resonant autodetachment, supported by Franck-Condon Factor (FCF) simulations. The phenylacetylide anion reacts with methyl iodide (CH3I) and allyl iodide (C3H5I) via SN2 nucleophilic displacement with measured rate coefficients of 4.29 and 3.66 × 10-10 cm3 molecule-1 s-1, respectively. The mechanisms associated with these displacement reactions are explained and understood in terms of the reaction kinetics, natural bond orbital (NBO) theory, and Density Functional Theory (DFT) calculations.

Ma, Howard Z.↗
NASA NTRS1996

A proof of concept investigation: A unique mobility spectrometer for In Situ diagnostics of positive and negative ion distributions in the mesosphere and lower ionosphere

We have carried out a proof-of-concept development and test effort that not only promises the reduction of parasitic effects of surface contamination (therefore increasing the integrity of 'in situ' measurements in the 60-130 km regime), but promises a uniquely expanded measurement set that includes electron densities, plasma conductivities, charged-particle mobilities, and mass discrimination of positive and negative ion distributions throughout the continuum to free-molecular-flow regimes. Three different sensor configurations were designed, built and tested, along with specialized driving voltage, electrometer and channeltron control electronics. The individual systems were tested in a variety of simulated space environments ranging from pressures near the continuum limit of 100 mTorr to the collisionless regime at 10(exp -6) Torr. Swept modes were initially employed to better understand ion optics and ion 'beam' losses to end walls and to control electrodes. This swept mode also helped better understand and mitigate the influences of secondary electrons on the overall performance of the PIMS design concept. Final results demonstrated the utility of the concept in dominant single-ion plasma environments. Accumulated information, including theoretical concepts and laboratory data, suggest that multi-ion diagnostics are fully within the instrument capabilities and that cold plasma tests with minimized pre-aperture sheath acceleration are the key ingredients to multi-ion success.

Szuszczewicz, Edward P.↗
NASA NTRSDate not supplied

Stable Chlorine Isotope Measurements of Astromaterials Using the Cs-Sputter Negative Ion Source of an Accelerator Mass Spectrometer

The volatile element Cl can be lost during the formation and evolution of planetary bodies, leading to fractionation of its two stable isotopes 35Cl and 37Cl. Chlorine isotope variations (reported as δ37Cl in parts per thousand (‰) relative to Standard Mean Ocean Chloride, SMOC) [1] are documented to exceed 80‰ [2] between different lunar rock samples and have been variably interpreted as the fingerprint of degassing during accretion, magma ocean, or volcanic portions of lunar history[3,4].The large intersample and intrasample variations observed by both bulk isotope ratio mass spectrometry (IRMS) and in-situ secondary ion mass spectrometry (SIMS) methods are difficult to interpret in part because of a paucity of bulk Cl isotope measurements (Figure 1).This lack of high-precision bulk data is due to the relative rarity of IRMS laboratories capable of making these high precision measurements on small samples of precious planetary materials such as those returned by human or robotic exploration. Here we present a new method for performing high precision δ37Cl measurements using the Cs-sputter negative ion source of an existing accelerator mass spectrometer. A brief description of the methods used for this work is followed by the results of our δ37Cl measurements and a discussion of the technique’s possible applications.

Chlorine↗
NASA NTRS1980

Properties of clusters in the gas phase. V - Complexes of neutral molecules onto negative ions

Ion-molecules association reactions of the form A(-)(B)n-1 + B = A(-)(B)n were studied over a range of temperatures in the gas phase using high pressure mass spectrometry. Enthalpy and entropy changes were determined for the stepwise clustering reactions of (1) sulfur dioxide onto Cl(-), I(-), and NO2(-) with n ranging from one to three or four, and onto SO2(-) and SO3(-) with n equal to one; and (2) carbon dioxide onto Cl(-), I(-), NO2(-), CO3(-), and SO3(-) with n equal to one. From these data and earlier hydration results, the order of the magnitude of the enthalpy changes on the association of the first neutral for a series of negative ions was found to parallel the gas-phase basicity of those anions.

Keesee, R. G.↗
DOE OSTI2024

In-house synthesized poly(ether ether ketone) ionenes. II. ToF-SIMS spectra in the negative ion mode

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to analyze poly(ether ether ketone) (PEEK) based membranes. PEEK membranes have been shown to be effective in the separation of CO 2 from flue gases (post-combustion technique). The PEEK membranes were synthesized using novel aromatic ether-ketone linkages inspired by PEEK with polymeric backbone bistriflimide [Tf2N]− counterions. One of the keys to advancing this technology is developing membranes that are selective and permeable toward CO 2 , in which PEEK based membranes have been shown to be. Furthermore, the compatibility between various water lean solvents also needs to be investigated. Surface analytical techniques such as x-ray photoelectron spectroscopy and ToF-SIMS are useful for investigating chemical changes between membranes. Herein, we present ToF-SIMS data obtained in the negative ion mode for four different PEEK membranes designed for use in CO 2 capture systems. Positive ion mode spectra are reported in Paper I.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Aluminum hydroxide, bayerite, boehmite, and gibbsite ToF-SIMS spectra in the negative ion mode. I

We report time-of-flight secondary ion mass spectrometry (ToF-SIMS) was performed for boehmite (AOH-60) and its potential products of oxidation including pseudo-boehmite (AOH-180), α- and γ-Al 2 O 3 , and α- and γ-Al(OH) 3 . Since boehmite is often incorporated on cladding materials to prevent corrosion, surface analysis techniques are performed to determine the amount of oxidation present. This ToF-SIMS spectral library is of significance because it includes boehmite and its potential oxidation products (i.e., aluminum oxide and hydroxide), which can be used to compare to spectra obtained for real-world samples containing boehmite. Furthermore, ToF-SIMS is often used as a complementary technique to x-ray photoelectron spectroscopy due to its surface sensitivity and ability to compare spectra via a multivariate analysis, therefore establishing that the molecular signatures of boehmite and relevant compounds are essential for peak identification. The SIMS spectra shown are acquired from commercially available powders, which were deposited onto a silicon wafer substrate via liquid slurry drop casting. This library of SIMS mass spectra will serve as a comparison of boehmite [γ-AlO(OH)], pseudo-boehmite [AlOOH∙nH 2 O], α- and γ-Al 2 O 3 aluminum oxide, and α- and γ-Al 2 O 3 aluminum hydroxide in the negative ion mode, which compliments those reported in the positive ion mode.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Negative ions from alkali hydrides as a source for H(-) beams

The production of H(-) ions by heating LiH powder in a high-temperature crucible was investigated experimentally and theoretically. It is found that the efficiency of H(-) ion production by this method is high. However, the theory for the negative surface ionization indicates that such high efficiency is not possible at crucible temperatures of about 750 C. The need for a further study of LiH ionization is emphasized.

Srivastava, S. K.↗