1. Inelastic collisions in molecular nitrogen at low temperature (2<=T<=50 K).
- Author
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Fonfría, J. P., Ramos, A., Thibault, F., Tejeda, G., Fernández, J. M., and Montero, S.
- Subjects
DEEP inelastic collisions ,NITROGEN ,MOLECULAR structure ,LOW temperatures ,COLLISIONS (Nuclear physics) ,POTENTIAL energy surfaces ,RAMAN spectroscopy - Abstract
Theory and experiment are combined in a novel approach aimed at establishing a set of two-body state-to-state rates for elementary processes ij→ℓm in low temperature N
2 :N2 collisions involving the rotational states i,j,ℓ,m. First, a set of 148 collision cross sections is calculated as a function of the collision energy at the converged close-coupled level via the MOLSCAT code, using a recent potential energy surface for N2 –N2 . Then, the corresponding rates for the range of 2≤=T≤=50 K are derived from the cross sections. The link between theory and experiment, aimed at assessing the calculated rates, is a master equation which accounts for the time evolution of rotational populations in a reference volume of gas in terms of the collision rates. In the experiment, the evolution of rotational populations is measured by Raman spectroscopy in a tiny reference volume (≈2×10-3 mm3 ) of N2 traveling along the axis of a supersonic jet. The calculated collisional rates are assessed experimentally in the range of 4≤=T≤=35 K by means of the master equation, and then are scaled by averaging over a large set of experimental data. The scaled rates account accurately for the evolution of the rotational populations measured in a wide range of conditions. Accuracy of 10% is estimated for the main scaled rates. [ABSTRACT FROM AUTHOR]- Published
- 2007
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