I have done theoretical studies on the dynamic processes relevant to the highly excited electronic states, of which energies are near and higher than the 1st ionization potential. The processes mainly studied are dissociative recombination (DR) and dissociative excitation (DE). of which mechanism is common to the other processes as rotational and vibrational excitation by electron impact. There is strong, quantum mechanical, and high density coupling between electronic and nuclear motion in those processes. I developed some theoretical methods to represent those complex processes, and made clear the mechanism of those processes and availability of the present methods by numerical calculation. The studied molecular systems are H_2 and HeH and those isotopes, which are typical two systems controlled by quite different mechanisms.
In the DR if HD^+ + e, its mechanism changes with collision energy. At the lower energy, I investigated the process including the rotational motion and estimating precisely the effect of nonadiabatic electronic resonance scattering. This result the first to represent the experimental structures. At the higher energy, I calculated the DR and DE cross sections by introducing the discretized dissociative basis functions to the usual multichannel quantum defect theory. Besides obtaining the atomic data, I show the common mechanism between the DR and DE.
The present study shows the reason of large cross section in the DR of HeH^+, where the dissociative resonance state is absent. The nonadiabatic coupling between the dissociative states could be represented by introducing the idea of closed dissociative channel. The present calculation reproduce the experimental spectrum and isotope dependence for the first time.