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NASA NTRS2018

The Detection of Hot Cores and Complex Organic Molecules in the Large Magellanic Cloud

We report the first extragalactic detection of the complex organic molecules (COMs) dimethyl ether (CH3OCH3) and methyl formate (CH3OCHO) with the Atacama Large Millimeter/submillimeter Array (ALMA). These COMs, together with their parent species methanol (CH3OH), were detected toward two 1.3 mm continuum sources in the N 113 star-forming region in the low-metallicity Large Magellanic Cloud (LMC). Rotational temperatures (Trot approx. 130 K) and total column densities (Nrot 10 approx. 16 cm−2) have been calculated for each source based on multiple transitions of CH3OH. We present the ALMA molecular emission maps for COMs and measured abundances for all detected species. The physical and chemical properties of two sources with COMs detection, and the association with H2O and OH maser emission, indicate that they are hot cores. The fractional abundances of COMs scaled by a factor of 2.5 to account for the lower metallicity in the LMC are comparable to those found at the lower end of the range in Galactic hot cores. Our results have important implications for studies of organic chemistry at higher redshift.

complex organic molecules↗
NASA NTRS2019

Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds

The Large and Small Magellanic Clouds (LMC and SMC), gas-rich dwarf companions of the Milky Way, are the nearest laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) under metal poor conditions. To date, only methanol, methyl formate, and dimethyl ether have been detected in these galaxies – all three toward two hot cores in the N113 star-forming region in the LMC, the only extragalactic sources exhibiting complex hot core chemistry. We describe a small and diverse sample of the LMC and SMC sources associated with COMs or hot core chemistry, and compare the observations to theoretical model predictions. Theoretical models accounting for the physical conditions and metallicity of hot molecular cores in the Magellanic Clouds have been able to broadly account for the existing observations, but fail to reproduce the dimethyl ether abundance by more than an order of magnitude. We discuss future prospects for research in the field of complex chemistry in the low-metallicity environment. The detection of COMs in the Magellanic Clouds has important implications for astrobiology. The metallicity of the Magellanic Clouds is similar to galaxies in the earlier epochs of the Universe, thus the presence of COMs in the LMC and SMC indicates that a similar prebiotic chemistry leading to the emergence of life, as it happened on Earth, is possible in low-metallicity systems in the earlier Universe.

Magellanic Clouds, star formation, astrochemistry,↗
NASA NTRS2019

Complex Organic Molecules in the Star-Forming Regions of the Magellanic Clouds

The Large and Small Magellanic Clouds (LMC and SMC), gas-rich dwarf companions of the Milky Way, are the nearest laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) under metal-poor conditions. To date, only methanol, methyl formate, and dimethyl ether have been detected in these galaxiesall three toward two hot cores in the N113 star-forming region in the LMC, the only extragalactic sources exhibiting complex hot-core chemistry. We describe a small and diverse sample of the LMC and SMC sources associated with COMs or hot-core chemistry, and compare the observations to theoretical model predictions. Theoretical models accounting for the physical conditions and metallicity of hot molecular cores in the Magellanic Clouds have been able to broadly account for the existing observations, but they fail to reproduce the dimethyl ether abundance by more than an order of magnitude. We discuss future prospects for research in the eld of complex chemistry in the low- metallicity environment. The detection of COMs in the Magellanic Clouds has important implications for astrobiology. The metallicity of the Magellanic Clouds is similar to that of galaxies in the earlier epochs of the universe; thus, the presence of COMs in the LMC and SMC indicates that a similar prebiotic chemistry leading to the emergence of life, as it happened on Earth, is possible in low-metallicity systems in the earlier universe.

Sewilo, Marta M.↗
NASA NTRS1991

The formation of oxygen-containing organic molecules in the Orion compact ridge

Following a suggestion of Blake et al. (1987), an attempt was made to account for the unusually large abundances of selected oxygen-containing organic molecules in the so-called 'compact ridge' source directed toward Orion KL by a gas-phase chemical model in which large amounts of water are injected into the source from the IRc2 outflow. Although quantitative model results show that the calculated abundances of methanol, methyl formate, and dimethyl ether can be enhanced relative to their values in the absence of water injection, the enhancements fall far short of explaining the very large observed abundances of these species. Models in which methanol is injected rather than water are more successful, although the source of the methanol is unclear.

Millar, T. J.↗
NASA NTRS1970

High energy density electrochemical cell

Primary cell has an anode of lithium, a cathode containing dihaloisocyanuric acid, and a nonaqueous electrolyte comprised of a solution of lithium perchlorate in methyl formate. It produces an energy density of 213 watt hrs/lb and can achieve a high current density.

Byrne, J. J.↗
NASA NTRS1971

Experimental interstellar organic chemistry: Preliminary findings

In a simulation of interstellar organic chemistry in dense interstellar clouds or on grain surfaces, formaldehyde, water vapor, ammonia and ethane are deposited on a quartz cold finger and ultraviolet-irradiated in high vacuum at 77K. The HCHO photolytic pathway which produces an aldehyde radical and a superthermal hydrogen atom initiates solid phase chain reactions leading to a range of new compounds, including methanol, ethanol, acetaldehyde, acetonitrile, acetone, methyl formate, and possibly formic acid. Higher nitriles are anticipated. Genetic relations among these interstellar organic molecules (e.g., the Cannizzaro and Tischenko reactions) must exist. Some of them, rather than being synthesized from smaller molecules, may be degradation products of larger organic molecules, such as hexamethylene tetramine, which are candidate consitituents of the interstellar grains. The experiments reported here may also be relevant to cometary chemistry.

Khare, B. N.↗
NASA NTRS1974

New reactions of paraformaldehyde and formaldehyde with inorganic compounds

Both paraformaldehyde and formaldehyde undergo reactions in the presence of several inorganic compounds to generate a variety of interesting organic products that can be important in chemical evolutionary processes. Some examples are acrolein, acetaldehyde, methyl formate, methanol, glycolaldehyde and formic acid. The organic compounds are produced at temperatures as low as 56 C and in high yield (up to 75%). The quantity produced depends principally on the nature of the inorganic compound, the ratio of the inorganic compound to paraformaldehyde, temperature and reaction time. The percent distribution of product depends on some of the foregoing factors.

Becker, R. S.↗
NASA NTRS1980

A search for the lowest-energy conformer of interstellar glycine

The first search for the lowest-energy conformation of interstellar glycine has been carried out. An emission line has been detected in Sgr B2 which is coincident in frequency with the J(K-K+) = 14(1, 14)-13(1, 13) transition of conformer I glycine; while the carrier of the observed line is uncertain, no other frequency-coincident species are known, and hence glycine cannot be ruled out. Several previously unidentified lines have been identified as methyl formate. Evidence for the existence of the elusive interstellar ethylene oxide, the only reported interstellar ring-structure molecule, is discussed.

Hollis, J. M.↗
NASA NTRS1981

A search for interstellar nitrous oxide

An extensive search for interstellar nitrous oxide (N2O) has been made at two different frequencies, 75.4 and 100.5 GHz, in a number of molecular sources. No N2O signal was detected; however, a number of other spectral lines including two new transitions of methyl formate and several new unidentified lines were measured.

Wilson, W. J.↗
NASA NTRS1991

Low temperature electrolytes for lithium/silver vanadium oxide cells

Combinations of methyl formate (MF) and propylene carbonate (PC) using salt concentrations of 0.6 to 2.4 M, with lithium hexafluoroarsenate and lithium tetrafluoroborate in a five to one molar ratio, were investigated as electrolytes in lithium/silver vanadium oxide batteries. The composition of the electrolyte affected cell performance at low temperature, self-discharge and abuse resistance as characterized by short circuit and crush testing. The electrolyte that provided the best combination of good low temperature performance, low cell self-discharge and abuse resistance was 0.6 M salt in 10:90 PC/MF.

Tuhovak, Denise R.↗
NASA NTRS1992

Symposium on High Power, Ambient Temperature Lithium Batteries, 180th Meeting of the Electrochemical Society, Phoenix, AZ, Oct. 13-17, 1991, Proceedings

Papers presented in these proceedings are on the state of the art in high-power lithium batteries, a design analysis of high-power Li-TiS2 battery, the performance and safety features of spiral wound lithium/thionyl chloride cells, the feasibility of a superhigh energy density battery of the Li/BrF3 electrochemical system, and an enhanced redox process of disulfide compounds and their application in high energy storage. Attention is also given to the structure and charge-discharge characteristics of mesophase-pitch based carbons, a study of carbons and graphites as anodes for lithium rechargeable cells, Li metal-free rechargeable Li(1+x)Mn2O4/carbon cells, and rechargeable lithium batteries using V6O13/V5O5 as the positive electrode material. Other papers discuss the electrochemical stability of organic electrolytes in contact with solid inorganic cathode materials, the electrochemical behavior of methyl formate solutions, and the interface between a solid polymer electrolyte and lithium anode.

Clark, W. D. K.↗
NASA NTRS1993

Interferometric observations for oxygen-containing organic molecules toward Orion-KL

High spatial resolution observations were made for the 3 mm transitions of methanol (CH3OH), methyl formate (HCOOCH3), and dimethyl ether (/CH3/2O) toward Orion-KL using the Nobeyama Millimeter Array. The 15(3)-14(4) A(-) CH3OH emission appears to be elongated along the line connecting IRc2 and 'the southern condensation (SC)', which may suggest a relation between methanol and the outflow from IRc2. The HCOOCH3 (7(1,6)-6(1,5)) and (CH3)2O (15(2,13)-15(1,14)) emissions appear to be well concentrated toward SC with an angular size of about 6.5 arcsec. There also exists another oxygen-rich condensation to the west of IRc2 having column densities of HCOOCH3 and (CH3)2O comparable to those of SC. We derive the total column densities 6.8 x 10 exp 16/sq cm, 1.4 x 10 exp 16/sq cm, and 2.7 x 10 exp 16/sq cm for CH3OH, HCOOCH3, and (CH3)2O, respectively, at the core of SC.

Minh, Y. C.↗
NASA NTRS1993

The spectrum of Orion-KL at 2 millimeters (150-160 GHz)

A spectral survey of Orion-KL has been carried out in the 2 mm atmospheric window in the frequency range 149.6-159.6 GHz, using the FCRAO 14 m telescope. Typical sensitivities achieved were T(sub A sup *) approximately 0.03-0.1 K, peak-to-peak. Over 180 spectral lines were detected, including approximately 45 unidentified features. The spectra were measured with a single-sideband receiver and, even at levels of T(sub A sup *) approximately 30 mK, are far from being confusion-limited. Fifteen known species were conclusively identified in Orion in this spectral region, with the largest numbers of lines arising from methyl formate, ethyl cyanide, methanol, and dimethyl ether. These species have beam-averaged column densities of N(sub tot) approximately 0.5-8 x 10(exp 15)/sq cm. Several other species have been tentatively observed, including acetaldehyde, C2S, and possibly EtOH. The large organic species, however, appear to arise from different regions. For example, CH3CCH and (CH3)2O come primarily from the extended ridge, while EtCN and VyCN exclusively arise in the hot core. This survey clearly demonstrates that the 2 mm window is rich in spectral lines. It also suggests there is much chemical selectivity in the formation of large organic interstellar molecules.

Ziurys, L. M.↗
NASA NTRS1995

Complex molecules in Sagittarius B2(N): The importance of grain chemistry

The complex molecules vinyl cyanide (CH2CHCN), methyl formate (HCOOCH3), and ethyl cyanide (CH3CH2CN) were observed in the Sgr B2 star-forming region with the BIMA millimeter wavelength array. A region with diameter less than 0.1 pc toward the Sgr B2(N) molecular core is found to be the major source of these molecules. Also, this source is coincident with continuum emission from dust and a center of H2O maser activity. Ultracompact (UC) H 11 regions are located within 0.1 pc. Strikingly, none of these molecules is detected toward Sgr B2(M), a core located 1 minute south of Sgr B2(N). The existence of complex molecules, a large mass of dust, high-velocity H2O masers, and UC H 11 regions strongly suggests that the Sgr B2(N) region has just begun to form stars, while the absence of strong dust emission and large molecules suggests Sgr B2(M) is more evolved. The detection of large molecules coincident with continuum emission from dust supports the idea found in current chemical models that grain chemistry is of crucial importance for the formation of these molecules.

Miao, Yanti↗
NASA NTRS2002

A Sensitive VLA Search for Small-Scale Glycine Emission Toward OMC-1

We have conducted a deep Q-band (lambda-7 mm) search with the Very Large Array (VLA) toward OMC-1 for the lowest energy conformation (conformer I) of glycine (NH2CH2COOH) in four rotational transitions: the 6(sub 15)- 5(sub 14), 6(sub 24)-5(sub 23), 7(sub 17- 6(sub 16), and 7(sub 07)-6(sub 06). Our VLA observations sample the smallest-scale structures to date in the search for glycine toward OMC-1. No glycine emission features were detected. Thus if glycine exists in OMC-1, either it is below our detection limit, or it is more spatially extended than other large molecules in this source, or it is primarily in its high energy form (conformer II). Our VLA glycine fractional abundance limits in OMC-1 are comparable to those determined from previous IRAM 30m measurements -- somewhat better or worse depending on the specific source model -- and the entire approximately 1 foot primary beam of the VLA was searched while sensitive to an areal spatial scale approximately 150 times smaller than the 24 inch beam of the IRAM single-element telescope. In the course of this work, we detected and imaged the 4(sub 14)-3(sub 13) A and E transitions of methyl formate (HCOOCH3) and also the 2(sub 02) - 1(sub 01) transition of formic acid (HCOOH). Since formic acid is a possible precursor to glycine, our glycine limits and formic acid results provide a constraint on this potential formation chemistry route for glycine in OMC-1.

Hollis, J. M.↗
NASA NTRS2011

Substituted Quaternary Ammonium Salts Improve Low-Temperature Performance of Double-Layer Capacitors

Double-layer capacitors are unique energy storage devices, capable of supporting large current pulses as well as a very high number of charging and discharging cycles. The performance of doublelayer capacitors is highly dependent on the nature of the electrolyte system used. Many applications, including for electric and fuel cell vehicles, back-up diesel generators, wind generator pitch control back-up power systems, environmental and structural distributed sensors, and spacecraft avionics, can potentially benefit from the use of double-layer capacitors with lower equivalent series resistances (ESRs) over wider temperature limits. Higher ESRs result in decreased power output, which is a particular problem at lower temperatures. Commercially available cells are typically rated for operation down to only 40 C. Previous briefs [for example, Low Temperature Supercapacitors (NPO-44386), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), p. 32, and Supercapacitor Electrolyte Solvents With Liquid Range Below 80 C (NPO-44855), NASA Tech Briefs, Vol. 34, No. 1 (January 2010), p. 44] discussed the use of electrolytes that employed low-melting-point co-solvents to depress the freezing point of traditional acetonitrile-based electrolytes. Using these modified electrolyte formulations can extend the low-temperature operational limit of double-layer capacitors beyond that of commercially available cells. This previous work has shown that although the measured capacitance is relatively insensitive to temperature, the ESR can rise rapidly at low temperatures, due to decreased electrolyte conductance within the pores of the high surface- area carbon electrodes. Most of these advanced electrolyte systems featured tetraethylammonium tetrafluoroborate (TEATFB) as the salt. More recent work at JPL indicates the use of the asymmetric quaternary ammonium salt triethylmethylammonium tetrafluoroborate (TEMATFB) or spiro-(l,l')-bipyrrolidium tetrafluoroborate (SBPBF4) in a 1:1 by volume solvent mixture of acetonitrile (AN) and methyl formate (MF) enables double-layer capacitor cells to operate well below -40 C with a relatively low ESR. Typically, a less than twofold increase in ESR is observed at -65 C relative to room-temperature values, when these modified electrolyte blends are used in prototype cells. Double-layer capacitor coin cells filled with these electrolytes have displayed the lowest measured ESR for an organic electrolyte to date at low temperature (based on a wide range of electrolyte screening studies at JPL). The cells featured high-surface-area (approximately equal to 2,500 m/g) carbon electrodes that were 0.50 mm thick and 1.6 cm in diameter, and coated with a thin layer of platinum to reduce cell resistance. A polyethylene separator was used to electrically isolate the electrodes.

Brandon, Erik J.↗
NASA NTRS2018

The Detection of Hot Cores and Complex Organic Molecules in the Large Magellanic Cloud

We report the first extragalactic detection of the complex organic molecules (COMs) dimethyl ether (CH3OCH3) and methyl formate (CH3OCHO) with the Atacama Large Millimeter/submillimeter Array (ALMA). These COMs, together with their parent species methanol (CH3OH), were detected toward two 1.3 mm continuum sources in the N 113 star-forming region in the low-metallicity Large Magellanic Cloud (LMC). Rotational temperatures (T(rot)~ 130 K) and total column densities (N(rot) ~ 10(exp 16) per sq. cm) have been calculated for each source based on multiple transitions of CH3OH. We present the ALMA molecular emission maps for COMs and measured abundances for all detected species. The physical and chemical properties of two sources with COMs detection, and the association with H2O and OH maser emission, indicate that they are hot cores. The fractional abundances of COMs scaled by a factor of 2.5 to account for the lower metallicity in the LMC are comparable to those found at the lower end of the range in Galactic hot cores. Our results have important implications for studies of organic chemistry at higher redshift.

astrochemistry – galaxies: star formation – Magell↗