Knowledge Bank

The homogeneous predissociation $C\to B$ in $N2+$ is treated theoretically in the adiabatic representation, where the coupling is produced by the nuclear kinetic energy operator. The electronic matrix elements of the operators $\partial /\partial R$ and $\partial 2/\partial R2$ are evaluated from results of ab initio CI calculations. These elements are strongly dependent on internuclear distance and behave very nearly as expected for a zero-order avoided crossing in the B and C states. Experimental RKR potentials are used to generate the nuclear motion wave functions, which are then used together with the ab initio electronic elements to calculate the vibronic overlap integrals. The calculated predissociative decay rates correctly reproduce the observed vibrational and isotopic dependence of the C-state predissociation. Similar calculations give the correct order of magnitude for an observed perturbation in $\nu =2$ of the C state, which lies below the predissociation limit.