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Date of Award

1978

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

G. W. King

Abstract

Two independently tunable dye lasers have been used to examine under high resolution two-photon sequential absorption processes for molecular iodine. One laser was used to pump selected rotational levels of the B state while the second laser excited transitions from the pumped level(s) to excited states of higher energy. Five separate electronic states which have ion-pair character have been examined in the 5 to 5.5eV energy region and their spectroscopic constants evaluated. Two of the excited states have 0g⁺ symmetry was identified by rotational analysis; the remaining three are either 0g⁺, 1g⁺, or possibly 2g⁺. At least three of these excited gerade states have been shown to likely contribute to previously reported emission spectra of iodine. A new two-photon method for the direct determination of molecular dissociation limits was developed from the sequential absorption studies described above. The technique permits selective excitation of rotational band structure near the convergence limit and is generally applicable to molecules with vibronic states (E) accessible by single-photon sequential absorption from an intermediate state (B). The amount of rotational structure which can be selectively displayed by the method can be adjusted by varying the ratio of the bandwidth of one of the exciting dye lasers to the E state rotational constant. This technique has been applied to analysis of the B⟵X iodine transition near dissociation and has provided an improved value for the B state dissociation limit. In addition, vibrational and rotational constants for energy levels near D are reported and applied to an investigation of the B state potential function at large internuclear distances.

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