Mechanism of Bond Rupture in HBr80 Following Isomeric Transition

The work of Hamill and Young (previous paper, this journal) has demonstrated that only a fraction of HBr⁸⁰(g) and DBr⁸⁰(g) bonds are ruptured following isomeric transition in Br⁸⁰. It is known that this transition is completely converted and from the theoretical work of Cooper it is to be expected that all Br⁸⁰ atoms should be separated from chemical combination. This paper presents a brief theoretical consideration of the rupture mechanism in HBr⁸⁰ in an attempt to understand why the rupture does not always occur. Approximate potential energy curves for some of the various molecular ions HBr^+z which form during the Auger shower following conversion have been constructed. It is found that there is a very great possibility that these ions all have lowest electronic states which are stable with respect to the dissociation process $${\mathrm{HBr}}^{\mathrm{+Z}}\to {\mathrm{H}}^{+}+{\mathrm{Br}}^{\text{+(Z−1)}},$$ and the possibility for nonrupturing is thus qualitatively explained for the charging process, since the entire charging time is short compared with molecular collision time in the gas phase. A further necessary condition for nonrupturing (as measured by Hamill and Young) is that the ions can be discharged in collisions without rupture. This process is also considered briefly. The complete rupture of the C–Br⁸⁰ bond (in CH₃Br⁸⁰(g)) is also considered and explained qualitatively. In this case no stable molecular states exist for the ions and rupture occurs during the charging process.