Non-Franck-Condon electron-impact dissociative-excitation cross sections of molecular hydrogen producingH(1s)+H(2l)throughX1Σg+(v=0)→{B1Σu+,B′1Σu+,C1Πu}

Abstract

Dissociation cross sections of H${}_{2}$ for high-energy electron impact (100--1000 eV) producing $H(1s)$, $H(2s)$, and $H(2p)$ for excitation from the ground vibrational state $(v=0)$ to the continuum of the ${B}^{1}{\ensuremath{\Sigma}}_{u}^{+}$, ${B}^{\ensuremath{'}}{}^{1}{\ensuremath{\Sigma}}_{u}^{+}$, and $C{}^{1}{\ensuremath{\Pi}}_{u}$ states were computed in the first Born approximation. Configuration-interaction electronic wave functions were used and vibrational degrees of freedom taken in account. The dissociative excitation cross sections as a function of the continuum energy for each final state were presented, and the accuracy of the wave function, including the importance of relaxation effects and the validity of the Franck-Condon approximation, is analyzed in comparison to available previous theoretical results. The computed dissociation cross sections were compared to experimental results making use of the separation of the various breakup channels proposed by Ajello, Shemansky, and James [Astrophys. J. 371, 422 (1991)]. The obtained cross sections to produce $\mathrm{H}(2p)+\mathrm{H}(1s)$ fragments via dissociative excitation to the $B$ and $C$ states have agreed well with the decomposed experimental results within the error bars. The dissociation cross sections to produce $\mathrm{H}(2s)+\mathrm{H}(1s)$ through the ${B}^{\ensuremath{'}}$ state were in most cases somewhat larger than the reported experimental error bars. In the most favorable case our theoretical ${B}^{\ensuremath{'}}$ dissociation cross section was 3.1% within the reported error bar at 300 eV electron impact energy. A possible experimental reason for this discrepancy was raised.