Quantum three-body calculation of nonresonant triple-α reaction rate at low temperatures

2010 ◽  
Author(s):  
Kazuyuki Ogata ◽  
Masataka Kan ◽  
Masayasu Kamimura ◽  
Isao Tanihara ◽  
Hooi Jin Ong ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Reaction Rate ◽  
Three Body

Quantum three-body calculation of nonresonant triple-α reaction rate at low temperatures

2010 ◽  
Author(s):  
Kazuyuki Ogata ◽  
Masataka Kan ◽  
Masayasu Kamimura ◽  
Hajime Susa ◽  
Marcel Arnould ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Reaction Rate ◽  
Three Body

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 Molecular Dynamics Calculation of the Thermodynamic Properties of Methane

1975 ◽  
Vol 28 (3) ◽  
pp. 315 ◽  
Author(s):  
HJM Hanley ◽  
RO Watts
Keyword(s):  
Molecular Dynamics ◽  
Thermodynamic Properties ◽  
Specific Heat ◽  
Low Temperatures ◽  
Spherically Symmetric ◽  
Method Of Molecular Dynamics ◽  
Experimental Values ◽  
Dynamics Calculation ◽  
Liquid States ◽  
Three Body

Thermodynamic properties of methane in the dense gas and liquid states have been calculated by the method of molecular dynamics. The methane pair interactions were modelled using a spherically symmetric m-6-8 potential, and the most significant three-body and quantum effects were included. Agreement between calculated and experimental values for the energy and pressure is generally good except at low temperatures and high densities. The specific heat at constant volume is also briefly discussed.

scholarly journals Astrophysical reaction rate forBe9formation within a three-body approach

2014 ◽  
Vol 90 (4) ◽  
Author(s):  
J. Casal ◽  
M. Rodríguez-Gallardo ◽  
J. M. Arias ◽  
I. J. Thompson
Keyword(s):  
Reaction Rate ◽  
Three Body ◽  
Astrophysical Reaction Rate

scholarly journals Ion-Molecule Reaction Studies below 80 K by the CRESU Technique

1987 ◽  
Vol 120 ◽  
pp. 19-23
Author(s):  
J. B. Marquette ◽  
B. R. Rowe ◽  
G. Dupeyrat ◽  
G. Poissant
Keyword(s):  
Low Temperatures ◽  
Reaction Rate ◽  
Thermal Conditions ◽  
Polar Molecule ◽  
Rate Coefficients ◽  
Third Body ◽  
Basic Principles ◽  
Molecule Reaction

The basic principles of the CRESU technique (Cinétique de Réactions en Ecoulement Supersonique Uniforme) are presented. This technique allows ion-molecule reaction rate coefficients under true thermal conditions at interstellar temperatures. Various behaviors of both third-body association and binary reactions with temperature have been observed, including ion-polar molecule reactions whose rate coefficients sharply increase at very low temperatures.

Negative ion – molecule reactions

1969 ◽  
Vol 47 (10) ◽  
pp. 1815-1820 ◽  
Author(s):  
E. E. Ferguson
Keyword(s):  
Charge Transfer ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Negative Ion ◽  
Transfer Reactions ◽  
Ion Molecule Reactions ◽  
Charge Transfer Reactions ◽  
Three Body ◽  
Interchange Reactions

Laboratory reaction rate constant measurements for negative ion – atom interchange reactions, negative ion charge transfer reactions, and negative ion three-body association reactions of aeronomic interest are reviewed and the available data tabulated. The present experimental techniques in use are briefly summarized. Most of the rate constants have been measured only at 300 °K; in a few cases data is available at energies [Formula: see text] as well as at 300 °K, so that an indication of the energy dependence of the rate constants is available.

Flash photolysis under non-isothermal conditions

1967 ◽  
Vol 45 (20) ◽  
pp. 2369-2374 ◽  
Author(s):  
George Burns
Keyword(s):  
Temperature Rise ◽  
Rate Constants ◽  
Recombination Rate ◽  
Reaction Rate ◽  
Flash Photolysis ◽  
Bromine Atom ◽  
Fold Increase ◽  
Reaction Vessel ◽  
Reaction Rate Constants ◽  
Three Body

The temperature rise which accompanies every flash photolytic reaction interferes with, and often makes impractical, measurements of the reaction rate constants. This difficulty may be partly overcome if the whole reaction vessel is uniformly irradiated by both the photolytic and the analyzing flash lamps.A flash photolysis apparatus with these characteristics was used to study bromine atom recombination. A 10 to 15 fold gain in atomic concentration, which corresponds to a 100 to 225 fold increase in three-body recombination rate, compared with the work of previous authors, was achieved with this apparatus. The reaction rate constants were determined from the changes in absorption of Br2 at either 4 035 Å or at 4 980 Å. The recombination rate constant of bromine in an excess of helium at 90 ± 20 °C was found to be equal to (0.8 ± 0.3)109 l2 mole−2 s−1 (measured at 4 980 Å) and (0.5 ± 0.1)109 l2 mole−2 s−1 (measured at 4 035 Å). The results suggest that the technique herein described can yield meaningful data, even though the reaction was accompanied by a 105 °C temperature rise. There was little heat exchanged between the reacting gas and the walls of the reaction vessel. Consequently the reaction vessel behaved as an effective calorimeter throughout the reaction.

Rheed Intensity Observation of AlAs and GaAs by in situ Etching Using Arsenic Tribromide

1995 ◽  
Vol 405 ◽  
Author(s):  
T. Kaneko ◽  
T. Säger ◽  
K. Eberl
Keyword(s):  
Low Temperatures ◽  
Reaction Rate ◽  
Etching Rate ◽  
Layer By Layer ◽  
Supply Rate ◽  
Limited Region ◽  
Continuous Increase ◽  
Higher Temperature ◽  
Rate Limiting

AbstractThe first in situ layer-by-layer etching of AlAs(100) surfaces has been observed by using RHEED intensity oscillations technique and is contrasted with the results obtained for the etching of GaAs(100). The experiments were conducted by introducing the etchant, arsenic tribromide, directly into a conventional MBE chamber without the use of any carrier gas. RHEED intensity oscillations during the etching of AlAs are observed between 350 and 760°C indicating a continuous increase in the etching rate with temperatures, with no supply rate limiting conditions being reached. Conversely, oscillations from GaAs reveal a reaction rate limited region at low temperatures (≤500°C) and a supply rate limited region at higher temperature(>500°C). The maximum selectivity in the etching rates between GaAs and AlAs is obtained at 450°C (40:1). The selectivity, and the ability to monitor the layer-by-layer process by RHEED intensity oscillations is foreseen to be of great importance for more controlled fabrications of AlAs and GaAs heterointerfaces.

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