Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)




A major portion of the high resolution photoabsorption spectrum of methyl iodide in the region between 49000 and 77000 cm('-1) has been analyzed by methods based on multichannel quantum defect theory (MQDT). Nearly all bands in this energy region can be assigned as members of molecular rydberg series which converge to the two lowest ionization limits of the molecule. However, it is also found that the Born-Oppenheimer separability of the totality of electronic surfaces is not nearly as complete as might be implied by the above results. Specifically, a nonrydberg, valence electronic state is shown to interact with the rydberg progressions and to produce anomalous intensity and position variations of the series members. Evidence is presented which indicates that this state, which is also observed in other alkyl halides, is related to the charge-transfer complex CH(,3)('+)I('-). Thus, the role of rydberg series as probes of the subtle dynamics of electrons in atoms is transferable to molecules, namely, to the simple halides, and these series constitute an important device with which to gauge the complicated dynamics of highly excited molecules. Further experimental and theoretical work which could extend our comprehension of these processes is discussed.