Electronic excitation of formaldehyde by low-energy electrons: A theoretical study using the complex Kohn variational method.

Abstract

We report results of a fully ab initio treatment of electronic excitation in a polyatomic molecule by electron impact. We have calculated total and differential cross sections for exciting the two lowest (n\ensuremath{\rightarrow}${\ensuremath{\pi}}^{\mathrm{*}}$${)}^{1}$,3${\mathrm{A}}_{2}$ excited states of ${\mathrm{H}}_{2}$CO for collision energies between 5 and 20 eV. The calculations were carried out in a three-state close-coupling approximation using the complex Kohn variational method. The absence of any backward peaking in the cross sections calculated for the $^{3}\mathrm{A}_{2}$ state is reminiscent of a rigorous selection rule for ${\ensuremath{\Sigma}}^{+}$-${\ensuremath{\Sigma}}^{\mathrm{\ensuremath{-}}}$ transitions in linear molecules. However, with no experimental studies available for comparison, the present results must be regarded as predictive.