SPIN-FORBIDDEN AND SPIN-ALLOWED ELECTRONICALLY NONADIABATIC PROCESSES IN DIATOMIC SYSTEMS

Abstract

The characterization of the electronic structure aspects of electronically nonadiabatic processes in diatomic molecules using algorithms we have developed for characterizing interstate, derivative couplings and relativistic interactions using large scale, $10^{5} - 10^{6}$ term, multireference Cl expansions is discussed. This data together with fully quantum mechanical treatments of the nuclear dynamics will be used to discuss predissociation in several diatomic systems, including $MgCl(A^{2}\Pi), ^{1}OH^{+}(c^{1}\Pi)^{2}$ and $NH(c^{2}\Pi)^{3}$ and state specific photodissociation in $OH(X^{2}\Pi) \rightarrow OH(A^{2} \Sigma^{+}) \rightarrow O(^{3}P_{3}) + H(^{2}S)$. The radiationless decay of $NH(c^{1}\Pi)$ and $OH^{+}(c^{1}\Pi)$ provide examples of systems in which the role of the dipolar spin-spin interaction must be considered in the decay mechanism.