scholarly journals Associative detachment (AD) paths for H and CN− in the gas-phase: astrophysical implications

2018 ◽  
Vol 20 (8) ◽  
pp. 5490-5500 ◽  
Author(s):  
Stanka V. Jerosimić ◽  
Franco A. Gianturco ◽  
Roland Wester
Keyword(s):  
Low Temperature ◽  
Gas Phase ◽  
Low Temperatures

The associative detachment reaction between H and CN− at low temperature becomes possible only along a selected range of approaching directions, thus showing that there is a preferential possibility at low temperatures of forming HCN in comparison with forming CNH.

Mechanism of the Direct Photochemical Decomposition of Thietane and its Derivatives in the Vapor Phase, in Solution, and in Glassy Matrices

1975 ◽  
Vol 53 (12) ◽  
pp. 1744-1755 ◽  
Author(s):  
David R. Dice ◽  
Ronald P. Steer
Keyword(s):  
Low Temperature ◽  
Gas Phase ◽  
Vapor Phase ◽  
Low Temperatures ◽  
Condensed Media ◽  
Photochemical Decomposition ◽  
Glassy Matrices

The direct photolyses of thietane, 3-ethyl-2-propylthietane, and 3-methylthietane in the vapor phase, in solution, and in glassy matrices at low temperatures have been examined. The effects of varying the photolysis wavelength, the temperature, the pressure and the phase of the substrate, and of adding inert thermalizers on the nature and yields of the various products have been measured. The results are interpreted in terms of initial C—S cleavage to give a 1,4-biradical which may, in the gas phase, decompose or ring close before complete equilibration of the various rotamers is achieved, or which may be thermalized in condensed media and trapped in glassy matrices at low temperature.

scholarly journals Low temperature gas phase reaction rate coefficient measurements: Toward modeling of stellar winds and the interstellar medium

2019 ◽  
Vol 15 (S350) ◽  
pp. 382-383
Author(s):  
Niclas A. West ◽  
Edward Rutter ◽  
Mark A. Blitz ◽  
Leen Decin ◽  
Dwayne E. Heard
Keyword(s):  
Low Temperature ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Low Temperatures ◽  
Reaction Rate ◽  
Rate Coefficient ◽  
Building Blocks ◽  
Rate Coefficients ◽  
Stellar Winds ◽  
Phase Reaction

AbstractStellar winds of Asymptotic Giant Branch (AGB) stars are responsible for the production of ∼85% of the gas molecules in the interstellar medium (ISM), and yet very few of the gas phase rate coefficients under the relevant conditions (10 – 3000 K) needed to model the rate of production and loss of these molecules in stellar winds have been experimentally measured. If measured at all, the value of the rate coefficient has often only been obtained at room temperature, with extrapolation to lower and higher temperatures using the Arrhenius equation. However, non-Arrhenius behavior has been observed often in the few measured rate coefficients at low temperatures. In previous reactions studied, theoretical simulations of the formation of long-lived pre-reaction complexes and quantum mechanical tunneling through the barrier to reaction have been utilized to fit these non-Arrhenius behaviours of rate coefficients.Reaction rate coefficients that were predicted to produce the largest change in the production/loss of Complex Organic Molecules (COMs) in stellar winds at low temperatures were selected from a sensitivity analysis. Here we present measurements of rate coefficients using a pulsed Laval nozzle apparatus with the Pump Laser Photolysis - Laser Induced Fluorescence (PLP-LIF) technique. Gas flow temperatures between 30 – 134 K have been produced by the University of Leeds apparatus through the controlled expansion of N2 or Ar gas through Laval nozzles of a range of Mach numbers between 2.49 and 4.25.Reactions of interest include those of OH, CN, and CH with volatile organic species, in particular formaldehyde, a molecule which has been detected in the ISM. Kinetics measurements of these reactions at low temperatures will be presented using the decay of the radical reagent. Since formaldehyde and the formal radical (HCO) are potential building blocks of COMs in the interstellar medium, low temperature reaction rate coefficients for their production and loss can help to predict the formation pathways of COMs observed in the interstellar medium.

scholarly journals Low Temperature Experiments on Gas-Phase Chemical Processes

2000 ◽  
Vol 197 ◽  
pp. 237-250 ◽  
Author(s):  
B. R. Rowe ◽  
C. Rebrion Rowe ◽  
A. Canosa
Keyword(s):  
Low Temperature ◽  
Reaction Kinetics ◽  
Gas Phase ◽  
Low Temperatures ◽  
Chemical Processes ◽  
Experimental Results ◽  
Phase Chemical

A review of the most recent experimental results concerning reaction kinetics at low temperatures is presented, most of them having been obtained using the CRESU technique. Some astrochemical consequences are also highlighted.

scholarly journals Synthetic Approaches to Complex Organic Molecules in the Cold Interstellar Medium

2022 ◽  
Vol 8 ◽  
Author(s):  
Eric Herbst ◽  
Robin T. Garrod
Keyword(s):  
Low Temperature ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Low Temperatures ◽  
Organic Molecules ◽  
High Energy ◽  
Interstellar Space ◽  
Interstellar Clouds ◽  
Millimeter And Submillimeter Waves ◽  
Complex Organic

The observation and synthesis of organic molecules in interstellar space is one of the most exciting and rapidly growing topics in astrochemistry. Spectroscopic observations especially with millimeter and submillimeter waves have resulted in the detection of more than 250 molecules in the interstellar clouds from which stars and planets are ultimately formed. In this review, we focus on the diverse suggestions made to explain the formation of Complex Organic Molecules (COMs) in the low-temperature interstellar medium. The dominant mechanisms at such low temperatures are still a matter of dispute, with both gas-phase and granular processes, occurring on and in ice mantles, thought to play a role. Granular mechanisms include both diffusive and nondiffusive processes. A granular explanation is strengthened by experiments at 10 K that indicate that the synthesis of large molecules on granular ice mantles under space-like conditions is exceedingly efficient, with and without external radiation. In addition, the bombardment of carbon-containing ice mantles in the laboratory by cosmic rays, which are mainly high-energy protons, can lead to organic species even at low temperatures. For processes on dust grains to be competitive at low temperatures, however, non-thermal desorption mechanisms must be invoked to explain why the organic molecules are detected in the gas phase. Although much remains to be learned, a better understanding of low-temperature organic syntheses in space will add both to our understanding of unusual chemical processes and the role of molecules in stellar evolution.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

INVAR M93

Alloy Digest ◽  
2008 ◽  
Vol 57 (1) ◽  
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Low Temperatures ◽  
Bend Strength ◽  
Temperature Performance ◽  
Ni Content ◽  
Precision Alloys ◽  
Ni Alloy

Abstract Invar is an Fe-Ni alloy with 36% Ni content that exhibits the lowest expansion of known metals from very low temperatures up to approximately 230 deg C (445 deg F). Invar M93 is a cryogenic Invar with improved weldability. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear and bend strength as well as fracture toughness and fatigue. It also includes information on low temperature performance as well as forming and joining. Filing Code: FE-143. Producer or source: Metalimphy Precision Alloys.

FEC-LiTFSI-Pyr1ATFSI Ionic Liquid Electrolyte to Improve Low Temperature Performance of Lithium-Ion Batteries

2014 ◽  
Vol 986-987 ◽  
pp. 80-83
Author(s):  
Xiao Xue Zhang ◽  
Zhen Feng Wang ◽  
Cui Hua Li ◽  
Jian Hong Liu ◽  
Qian Ling Zhang
Keyword(s):  
Low Temperature ◽  
Lithium Ion Batteries ◽  
Low Temperatures ◽  
Freezing Point ◽  
Lithium Ion ◽  
Liquid Electrolyte ◽  
Capacity Retention ◽  
Composite Electrolyte ◽  
Ionic Liquid Electrolyte ◽  
Fluoroethylene Carbonate

N-methyl-N-allylpyrrolidinium bis (trifluoromethanesulfonyl) imide (PYR1ATFSI) with substantial supercooling behavior is synthesized to develop low temperature electrolyte for lithium-ion batteries. Additive fluoroethylene carbonate (FEC) in LiTFSI/PYR1ATFSI/EC/PC/EMC is found that it can reduce the freezing point. LiFePO4/Li coin cells with the FEC-PYR1ATFSI electrolyte exhibit good capacity retention, reversible cycling behavior at low temperatures. The good performance can be attributed to the decrease in the freezing point and the polarization of the composite electrolyte.

Aqueous Benzene Oxidation in Low-Temperature Plasma of Pulsed Corona Discharge

2016 ◽  
Vol 19 (2) ◽  
Author(s):  
Iakov Kornev ◽  
Sergei Preis
Keyword(s):  
Low Temperature ◽  
Corona Discharge ◽  
Gas Phase ◽  
Pulse Repetition Frequency ◽  
Repetition Frequency ◽  
Pulse Repetition ◽  
Benzene Oxidation ◽  
Low Temperature Plasma ◽  
Temperature Plasma ◽  
Pulsed Corona

AbstractWastewaters polluted with non-biodegradable volatile organic compounds (VOCs), such as aromatic substances, present a growing problem meeting no adequately affordable technological response. Low-temperature plasma generated in the gas-phase pulsed corona discharge (PCD) presents competitive advanced oxidation technology in abatement of various classes of pollutants, although the process parameters, the pulse repetition frequency and the liquid spray rate, require optimization. The experimental research into aqueous benzene oxidation with PCD was undertaken to establish the impact of the parameters to the energy efficiency. The oxidation reaction was found under the experimental conditions to mostly proceed in the gas phase showing little influence of the pulse repetition frequency and the gas-liquid contact surface. Oxidation of benzene and, presumably, other volatile pollutants in the volume of PCD reactor compartment presents an effective strategy of aqueous VOCs abatement.

Anthracene fluorescence at low temperatures. I. Purified single crystals

1972 ◽  
Vol 25 (7) ◽  
pp. 1411 ◽  
Author(s):  
LE Lyons ◽  
LJ Warren
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Fluorescence Spectrum ◽  
Low Temperatures ◽  
Free Exciton ◽  
Deformation Bands ◽  
Exciton Emission ◽  
Polarized Emission ◽  
Impurity Bands ◽  
Phonon Structure

The low-temperature fluorescence spectrum of purified vapour-grown anthracene single crystals is presented and the free-exciton emission distinguished from a number of defect or impurity bands present even in the purest crystals. In assigning the observed bands the symmetry of the active vibrations and the origin of background fluorescence and deformation bands are discussed. The phonon structure in the region of the fluorescence origin was found to be almost completely b-polarized. Emission of electronic origin (25103 cm-1) was too weak to be observed. Polarization ratios of the principal vibronio bands at 5.6 K are given.

Desiccation and low temperature attenuate the effect of UVC254 nm in the photobiont of the astrobiologically relevant lichens Circinaria gyrosa and Buellia frigida

2014 ◽  
Vol 14 (3) ◽  
pp. 479-488 ◽  
Author(s):  
T. Backhaus ◽  
R. de la Torre ◽  
K. Lyhme ◽  
J.-P. de Vera ◽  
J. Meeßen
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Photosynthetic Activity ◽  
Real Space ◽  
Fast Recovery ◽  
Protective Mechanisms ◽  
Subzero Temperatures ◽  
High Viability ◽  
Buellia Frigida ◽  
Insight Into

AbstractSeveral investigations on lichen photobionts (PBs) after exposure to simulated or real-space parameters consistently reported high viability and recovery of photosynthetic activity. These studies focused on PBs within lichen thalli, mostly exposed in a metabolically inactive state. In contrast, a recent study exposed isolated and metabolically active PBs to the non-terrestrial stressor UVC254 nm and found strong impairment of photosynthetic activity and photo-protective mechanisms (Meeßen et al. in 2014b). Under space and Mars conditions, UVC is accompanied by other stressors as extreme desiccation and low temperatures. The present study exposed the PBs of Buellia frigida and Circinaria gyrosa, to UVC in combination with desiccation and subzero temperatures to gain better insight into the combined stressors' effect and the PBs' inherent potential of resistance. These effects were examined by chlorophyll a fluorescence which is a good indicator of photosynthetic activity (Lüttge & Büdel in 2010) and widely used to test the viability of PBs after (simulated) space exposure. The present results reveal fast recovery of photosynthetic activity after desiccation and subzero temperatures. Moreover, they demonstrate that desiccation and cold confer an additional protective effect on the investigated PBs and attenuate the PBs' reaction to another stressor – even if it is a non-terrestrial one such as UVC. Besides other protective mechanisms (anhydrobiosis, morphological–anatomical traits and secondary lichen compounds), these findings may help to explain the high resistance of lichens observed in astrobiological studies.

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