PHOTOFRAGMENT TRANSLATIONAL SPECTROSCOPY OF N-BUTYL IODIDE AT 277 AND 304 NM - POLARIZATION DEPENDENCE AND ENERGY PARTITIONING

Abstract

Photodissociation of n-C4H9I at excitation wavelengths of 277 and 304 nm has been studied utilizing state-selective photofragment translational spectroscopy. The quantum yields of I*(P-2(1/2)) at these wavelengths are determined to be 0.61 and 0.14, respectively. The anisotropy parameters observed at 277 nm are ($) over bar beta(I) = 1.6 +/- 0.1 for the ground-state I(P-2(3/2)) and ($) over bar beta(I*) = 0.9 +/- 0.1 for the excited-state I*(P-2(1/2)) which substantially differs from the limiting value. The results are interpreted in terms of dual path formation of iodine atoms from two different excited (3)Q(0) and (1)Q(1) states, i.e., a direct and an indirect dissociation via curve crossing between these states. The ($) over bar beta(I) (= 1.9 +/- 0.1) at 304 nm, close to its limiting value, shows that the primary processes for I and I* formation channels proceed dominantly via a parallel transition to the (3)Q(0) State in the long-wavelength region of the A band absorption profile. The translational energy distributions-of recoil fragments show that a large fraction of the available energy goes into the internal excitation of the photofragment ([E(int)]/E(avl) similar or equal to 0.7) for both dissociation channels. The quantitative analysis is presented for the state-dependent branching ratio and curve crossing probability combined with a quasidiatomic Landau-Zener description.