Rotational (de)-excitation of C5 by collision with He at low temperature

2021 ◽  
Author(s):  
A. Chefai ◽  
M. Ben Khalifa ◽  
F. Khadri ◽  
K. Hammami
Keyword(s):  
Low Temperature ◽  
Interstellar Medium ◽  
Rate Coefficients ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

An appropriate estimation of the abundance of the observed C5 radical in the interstellar medium requires accurate radiative and collisional rate coefficients.

scholarly journals The molecular universe: from observations to laboratory and back

2015 ◽  
Vol 11 (A29A) ◽  
pp. 299-304
Author(s):  
Ewine F. van Dishoeck
Keyword(s):  
Solid State ◽  
Interstellar Medium ◽  
Theoretical Data ◽  
Basic Data ◽  
Rate Coefficients ◽  
Molecular Processes ◽  
Molecular Astrophysics ◽  
Collisional Rate Coefficients ◽  
Collisional Rate ◽  
New Facilities

AbstractThis brief overview stresses the importance of molecular processes in modern astrophysics and provides examples where the availability of new laboratory or theoretical data proved crucial in the analysis. This includes basic data such as spectroscopy and collisional rate coefficients, but also an improved understanding of reactions and photoprocesses in the gaseous and solid state. In spite of many lingering uncertainties, the future of molecular astrophysics is bright with new facilities such as ALMA, JWST and ELTs on the horizon. Together, they will allow increased understanding of the journey of gas and solids from clouds to stars and planets, and back to the interstellar medium.

Investigation of amino acetonitrile (NH2CH2CN) — a precursor of glycine, in the interstellar medium

2020 ◽  
Vol 98 (3) ◽  
pp. 243-250
Author(s):  
Mohit K. Sharma
Keyword(s):  
Interstellar Medium ◽  
Transition Probabilities ◽  
Rate Coefficients ◽  
Radiative Transitions ◽  
Large Velocity ◽  
Centrifugal Distortion Constants ◽  
Collisional Rate Coefficients ◽  
Large Velocity Gradient ◽  
The Universe ◽  
Collisional Rate

Known values of rotational and centrifugal distortion constants, in conjunction with electric dipole moment, have been used to calculate energies for the ground rotational levels, ground vibrational state, and ground electronic state of amino acetonitrile (NH2CH2CN), which is of interest for studies of life in the universe. Probabilities for radiative transitions between the rotational levels are also calculated. Such transition probabilities are used in conjunction with scaled values for the collisional rate coefficients for large velocity gradient calculations. A line 110–111 at 450.31 MHz is found to show anomalous absorption. Two observed lines 909–808 at 80.947 GHz and 120,12–110,11 at 107.283 GHz, and another nine lines, 918–817, 716–615, 817–716, 919–818, 1019–918, 808–707, 100,10–909, 110,11–100,10, and 707–606, are found to show emission features. There are several other observed lines, which are found weaker than these 11 lines. These 10 additional lines may help in the identification of amino acetonitrile in the interstellar medium.

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.

Calculations of fine-structure resolved collisional rate coefficients for the NH(X3Σ−)-He system

2011 ◽  
Vol 134 (2) ◽  
pp. 024305 ◽  
Author(s):  
Robert Toboła ◽  
Fabien Dumouchel ◽  
Jacek Kłos ◽  
François Lique
Keyword(s):  
Fine Structure ◽  
Rate Coefficients ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

Collisional-Rate Coefficients for Sodiumlike Ar viii Ions

1972 ◽  
Vol 6 (1) ◽  
pp. 38-44 ◽  
Author(s):  
R. U. Datla ◽  
H. -J. Kunze ◽  
D. Petrini
Keyword(s):  
Rate Coefficients ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

Collisional excitation of H2S by molecular hydrogen

2020 ◽  
Vol 494 (4) ◽  
pp. 5239-5243
Author(s):  
Paul J Dagdigian
Keyword(s):  
Energy Surface ◽  
Rate Coefficients ◽  
Cluster Method ◽  
Quantum Scattering ◽  
Collisional Excitation ◽  
Close Coupling ◽  
Accurate Knowledge ◽  
Explicitly Correlated ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

ABSTRACT Accurate estimates of the abundance of H2S, and inferences about the unmeasured H2 density, require accurate knowledge of radiative and collisional rate coefficients. Time-independent close-coupling quantum scattering calculations have been employed to compute rate coefficients for (de-)excitation of para- and ortho-H2S in collisions with para- and ortho-H2. These calculations utilized a potential energy surface for the interaction of H2S with H2 recently computed by the explicitly correlated CCSD(T)-F12a coupled-cluster method. Rate coefficients for temperatures ranging from 5 to 500 K were calculated for all transitions among the first 19 rotational levels of H2S, whose energies are less than or equal to 405 K. These rate coefficients are compared with previous estimates of these quantities.

scholarly journals Measurements of Collisional Rate Coefficients in Laboratory Plasmas

1972 ◽  
Vol 14 ◽  
pp. 565-583 ◽  
Author(s):  
H.-J. Kunze
Keyword(s):  
Theoretical Calculations ◽  
Experimental Results ◽  
Experimental Techniques ◽  
Rate Coefficients ◽  
Line Radiation ◽  
Laboratory Plasmas ◽  
Plasma Device ◽  
Collisional Rate Coefficients ◽  
Collisional Rate

AbstractLine radiation emitted by highly ionized atoms embedded in hot laboratory plasmas can be utilized to obtain collisional rate coefficients for excitation and ionization. After a discussion of the principles underlying these measurements, the plasma device mostly used is explained briefly as are the various experimental techniques. All experimental results obtained so far are finally discussed and compared with theoretical calculations where possible.

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