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.

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 The periodic table – an experimenter’s guide to transactinide chemistry

2019 ◽  
Vol 107 (9-11) ◽  
pp. 865-877 ◽  
Author(s):  
Robert Eichler
Keyword(s):  
Research And Development ◽  
Gas Phase ◽  
Periodic Table ◽  
Chemical Properties ◽  
Superheavy Elements ◽  
Experimental Results ◽  
Chemical Studies ◽  
Phase Chemical

Abstract The fundamental principles of the periodic table guide the research and development of the challenging experiments with transactinide elements. This guidance is elucidated together with experimental results from gas phase chemical studies of the transactinide elements with the atomic numbers 104–108 and 112–114. Some deduced chemical properties of these superheavy elements are presented here in conjunction with trends established by the periodic table. Finally, prospects are presented for further chemical investigations of transactinides based on trends in the periodic table.

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 A rapid, spatially dispersive frequency comb spectrograph aimed at gas phase chemical reaction kinetics

2020 ◽  
Vol 118 (16) ◽  
pp. e1733116 ◽  
Author(s):  
Frances C. Roberts ◽  
H. J. Lewandowski ◽  
Billy F. Hobson ◽  
Julia H. Lehman
Keyword(s):  
Reaction Kinetics ◽  
Gas Phase ◽  
Chemical Reaction ◽  
Frequency Comb ◽  
Chemical Reaction Kinetics ◽  
Spatially Dispersive ◽  
Phase Chemical

A Chemical Study of Photo-CVD of Silicon Nitride in Mercury-Sensitized Reactions Between Silane and Ammonia

1987 ◽  
Vol 101 ◽  
Author(s):  
Ching-Hsong Wu
Keyword(s):  
Silicon Nitride ◽  
Gas Phase ◽  
Isotope Labeling ◽  
Chemical Study ◽  
Chemical Processes ◽  
Chemical Characteristics ◽  
Experimental Conditions ◽  
Transient Intermediates ◽  
Labeling Method ◽  
Phase Chemical

ABSTRACTA photochemical system of mercury-sensitized reactions between silane and ammonia was studied to elucidate the gas-phase chemical processes involved in photo-CVD of silicon nitride. Several transient intermediates were detected and identified as silylated amines by the mass spectrometric isotope labeling method. These compounds containing both Si and N atoms appeared to be the precursors of silicon nitride. The chemical characteristics of silylated amines were studied under different experimental conditions. The reactivity and possible reaction paths for the formation of silylamine are discussed.

Magnon drag and the low temperature thermopower of GeMnTe

1978 ◽  
Vol 56 (5) ◽  
pp. 497-500
Author(s):  
A. Cafaro ◽  
F. T. Hedgcock ◽  
W. B. Muir
Keyword(s):  
Low Temperature ◽  
Experimental Evidence ◽  
Thermoelectric Power ◽  
Low Temperatures ◽  
Impurity Scattering ◽  
Experimental Results ◽  
Phonon Drag ◽  
Degenerate Semiconductors ◽  
Upper Limit

The thermoelectric power of pure GeTe and GeMnTe containing 1 and 5at.% Mn has been measured between 25 and 2.5 K. The manganese doped Ge–Te alloys ferromagnetically order at low temperatures and theoretical estimates of the magnon drag contribution to the thermopower in these degenerate semiconductors is 60 μV/K. When appropriate allowance is made for the effects of impurity scattering on the phonon drag thermopower there appears to be no experimental evidence for a magnon drag contribution to the thermopower of this magnitude. An upper limit for the magnon drag contribution to the thermopower estimated from the experimental results for these materials is 0.5 μV/K.

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.

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