Analytical Treatment of the K Matrix Integral Equation in the Dynamics of Superexcited Molecules

Abstract

Superexcited states (SES) constitute one peculiar class of electronically highly excited states of molecules whose internal energies exceed the corresponding lowest ionization potentials.1, 2, 3 They play important roles in various fields of chemistry and physics as intermediate states of dynamic processes. Fig. 1 shows a schematic view of this feature. It is crucial to understand the characteristics of the central SES M*, in order to systematically comprehend the various dynamic processes. Dissociative recombination represents one of several good examples. According to the difference in the autoionization mechanisms, the SES are classified into the following two kinds: (i) multiply or inner-shell excited states, which are called “SES of the first kind”, and (ii) rovibrationally excited Rydberg states, which is called “SES of the second kind.” The dynamics of SES are governed by the two basic interactions: the electronic coupling, V(R, e), between the first kind of SES and the electronic continuum, and the quantum defect function µ(R), where R is the internuclear distance and e is the electron energy. If these two quantities are available together with the potential curves E d(R) of the first kind of SES, then the MQDT (multi-channel quantum defect theory) presents a very powerful tool to investigate the various dynamics. These quantities should be basically evaluated by quantum chemical electronic structure theory, but it is not easy to obtain accurate absolute values, especially in the case of V(R, e).