Kinetic Energy Release Effects on the Angular Distributions from the Photoionization of H$_2^+$

Recent experimental and theoretical work examining the double photoionization of H$_2$ has uncovered surprising changes in the resulting differential cross sections as the kinetic energy released to the outgoing protons is varied. In this work, a complementary study is made of the angular distributions arising from the photoionization of H$_2^+$ at various internuclear separations $R$. Different internuclear separations correspond to different amounts of kinetic energy released to the exploding protons. We find that the angular distributions for the $\sigma \rightarrow \pi$ transition in H$_2^+$ are relatively insensitive to changes in $R$, but that the angular distributions for the $\sigma \rightarrow \sigma$ transition display dramatic variations with $R$. The reasons for this effect and the connections with early work on H$_2^+$ photoionization will be discussed.