Studies of the Spectroscopy and Collision Dynamics of Some Ion-Pair States of Iodine Using Laser Optical-Optical Double Resonance Excitation.

Available from UMI in association with The British Library. Requires signed TDF. The spectroscopy of the f(0_sp {g}{+}) ion-pair state of I _2 was studied in detail and dispersed fluorescence spectra obtained for a range of single rovibronic levels, up to v^' = 88. The electronic transition dipole moment function, mu_{21}(r), has been determined from direct simulation of the transition f(0_sp{g}{+}, v ^' = 88, J^' = 70) to B(0_sp {rm u}{+}, v^ {''} = n). mu_{21}(r) displays a maximum close to r_{e} for the f state, but decreases on going to smaller and larger internuclear separations. This has been explained using LCAO and separated-ion descriptions for the molecular electronic wavefunctions. Product state vibrational distributions have been determined for collisional relaxation of I_2(f0_sp{g}{+}) by I_2(X0_sp{g} {+}). These distributions are interpreted in terms of an orbiting-controlled and a long range resonant model for the transfer into the F(0_sp {u}{+}) state. New fluorescence emission systems have been observed following excitation of the lowest vibrational levels of the E(0_sp{g}{+} ), beta(1_{g}), gamma(1_{u} ) ion-pair states of I_2. These systems have been assigned from measurements of line positions and by direct spectral simulations. Following this, several previously unidentified features in the emission spectrum of I_2, in the presence of argon, have been assigned. Finally, the excitation function for formation of XeI*(B^2sigma_{1/2 }), following OODR excitation of Xe/I _2 mixtures, has been measured as a function of vibrational level in the f(0_sp {g}{+}) ion-pair state. State -specific rate constants for reaction and total removal have been estimated, assuming a radiative lifetime of 20 ns for the f(0_sp{g}{+ }) state. These indicate that the branching ratio for reaction is a function of excitation energy. A simple harpooning model was employed in order to explain the observation that the yield of XeI* increases as a function of vibronic energy.