Electron and photon dissociation cross sections of the H2 singlet ungerade continua

Abstract

Photodissociation cross sections and oscillator strengths for H2 from the X 1Σ+g (vi, Ji) levels to the continuum levels of the B 1Σ+u, C 1Πu, B, D′ 1Πu and 5pσ 1Σ+u states have been calculated. The (vi, Ji) state-specific electron impact dissociation cross sections to the continuum levels of these states have been obtained for the first time over a wide energy range using calculated continuum oscillator strengths along with previously published excitation functions of the Lyman and Werner bands. Estimated cross sections to the higher (n ⩾ 5) npσ 1Σ+u and npπ 1Πu continua are also provided. Both photon and electron impact excitation cross sections show strong dependences on the initial (vi, Ji) quantum numbers. Thermally averaged electron impact cross sections of all singlet ungerade states increase monotonically with temperature. While excitation to the B′ 1Σ+u continuum is the dominant dissociation channel at room temperature, the C 1Πu and B 1Σ+u continua become more important at high temperature (>5000 K). This work, along with the previous calculation of the B′ 1Σ+u and D 1Πu states by Liu et al (2009a J. Phys. B: At. Mol. Opt. Phys. 42 185203), provides the complete electron impact dissociation cross section of H2 through the singlet ungerade continua. Electron dissociation cross sections of the singlet ungerade continua are provided for the purpose of modelling atmospheric heating, analysis of occultation measurements and the hot atomic hydrogen plume observed at Saturn.