Improved Hybrid Theory Calculation of e-N2 Vibrational Excitation
I will describe some new calculations on e−-N2 vibrational excitation using hybrid theory. When we did our original calculations1 and obtained vibrational excitation cross sections, we were faced with the problem that some upper-atmospheric physicists at Goddard actually wanted to use them; they wanted accurate normalized vibrational excitation cross sections. I would have liked to advise them to use the experimental results; unfortunately, the experimental normalizations are not as yet unique. The situation is demonstrated in Figure 1. The curves on the left are essentially Schulz’s original ones.2 They were differential cross sections measured at 72° as a function of energy and the normalization was arbitrary. However, assuming the total cross sections had the same shape as a function of energy (and this is an excellent approximation“), Schulz pointed out that if you use the values (in Å2) given on the ordinate, Figure la, then you get agreement with previous experimental results of Haas.3 Subsequently, Schulz4 renormalized these curves based on later absolute measurements of Spence et al.5 which is given in Figure lb, and you see they are a factor of two larger. In the same article4 Schulz also showed a figure based on work that S. F. Wong has done which, after conversion to total cross section using our dσ/dΩ gives a normalization yet another factor of two larger. In fact, that normalization in Figure lc is almost identical to what Chandra and I got in our original hybrid calculation1 But in view of the other normalizations, as well as uncertainties in our calculation, I could only advise caution to our atmospheric colleagues and promise them a better calculation. What I’d like to describe here is a preliminary report of this new calculation.
KeywordsTotal Cross Section Differential Cross Section Partial Wave Vibrational Excitation Elastic Cross Section
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- 4.G. J. Schulz, in Principles of Laser Plasmas (John Wiley and Sons, (1976)).Google Scholar
- 7.These results are unpublished; they appear in the Ph.D. thesis of L. Dube, Yale University, Jan. 1978. The results were first presented by the authors at IX ICPEAC, Abstracts of Papers (University of Washington Press, 1975), p. 264. Our own results (Ref. 1) were also presented there ibid, p. 267.Google Scholar
- 9.P. G. Burke and N. Chandra, J. Phys. B 5, 16 and 6 (1972).Google Scholar
- 12.Cf. Refs. 7 and 8 and L. Dube and A. Herzenberg (to be published).Google Scholar