## LSU Historical Dissertations and Theses

1989

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Chris H. Greene

#### Abstract

A new model for a class of heteronuclear diatomic molecules is presented. This model readily combines multichannel quantum defect theory (MQDT) with a nonperturbative Fermi-type analysis. Applications to a series of alkali-He dimers, such as CsHe, have shown that this very simple model can give results (e.g. Born-Oppenheimer potential curves) very close to those from more elaborated methods (e.g. $\ell$-dependent pseudopotential method). Applications to heteronuclear rare gas dimers, such as ArXe, give the first detailed interpretation and classification of some of the observed spectra, which are too complicated to be studied by conventional molecular methods. Another MQDT application is also presented. The photoionization of HD is studied with a method that has been well developed for H$\sb2$. The use of the same method as that for H$\sb2$ results in the conclusion that the g-u mixing effect in HD is negligible in energy regions far from dissociation thresholds. Some experimental observations of HD photoionization are accounted for in great detail by this theoretical study.

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