Evaluation of electron impact excitation of N2 X 1Σg+(0) into the N2+ X 2Σg+(v), A 2Πμ(v), and B 2Σu+(v) states -: art. no. A07307

Published experimental integrated electric dipole photoionization oscillator strengths (f(ij)) have been applied to the determination of absolute electron impact excitation cross sections of the N-2 X (1)Sigma(g)(+)(0) state into the N-2(+) X (2)Sigma(g)(+)(v), A (2)Pi(u)(v), and B (2)Sigma(u)(+)(v) states. The required relative electron impact cross section shape functions from threshold to energy values, limited by the imposition of relativistic effects at the high end, are established in this work by extracting accurate analytic functions from a critical review of extensive published experimental results. The cross sections examined here are important benchmarks used in establishing absolute values for critical rate processes in aeronomy. The determination of the absolute cross sections using the derived f(ij) is accomplished through the physical relationship to a modified Born approximation analytic function that defines the electron impact shape functions. The zero order term of the analytic function is established in value relative to the remaining terms through shape analysis of the experimental electron impact results. The value of f(ij) fixes the absolute value of the zero order term, determining the cross sections over the entire electron impact energy range. It is argued that this methodology is the most accurate approach at this time because of the existence of the intrinsically more accurate photometrically dermined f(ij). The critical quantities in atmospheric process applications are the branching ratios of excitation into the N-2(+) X (2)Sigma(g)(+), A (2)Pi(u), and B (2)Sigma(u)(+) states. The N-2(+) (X (2)Sigma(g)(+), A (2)Pi(u), B (2)Sigma(u)+) partitioning within the total ionization cross section has been a source of disagreement in the literature, in spite of the fact that substantial effort has been expended in establishing acceptably accurate values. The present work establishes accurate cross sections for these states over the entire practical energy range required for research in atmospheric N-2 physical chemistry. The accuracy of the results obtained here are verified by consistency with the most reliably established past experimental electron impact cross sections, in agreement with the independently established total N-2(+) cross section. We provide analytic collision strengths for the vibrational levels of the N-2(+) X (2)Sigma(g)(+), A (2)Pi(u), and B (2)Sigma(u)(+) states, allowing establishment of rate coefficients for the system, at an estimated error <=+/- 8%.