Dissociative recombination angular distributions

Abstract

The angular distributions of the products of dissociative recombination of diatomic molecular ions are derived. The distributions are determined by the dominant partial waves of the captured electrons. For a single dominant wave, the neutral product distribution is described by the same spherical harmonic that describes the electron partial wave. The derived distributions take into account both direct and indirect dissociative recombination and are essential for modeling the projected distributions measured in storage ring experiments. All prior storage ring experiments have assumed that the product angular distributions can be described by spherical harmonics with angular momenta ≤ 1 and isotropic product distributions for "zero" eV electron capture. These assumptions are tested here by deriving the projected distributions for the dissociative recombination of CH+. For CH+, it is shown that the "zero" eV storage ring experimental results cannot be explained by only isotropic dissociation. Instead, an anisotropic model product distribution is required. The anisotropic model yields a quantum yield of 1.0 for C(1D) instead of the incorrect value of 0.79 derived previously using an isotropic model. The quantum yields of all prior storage ring experiments on other molecular ions at "zero" eV electron energy must be reassessed in view of these findings.