RESOLUTION OF 3 OPTICALLY-ACTIVE COMPONENTS OF THE TRANSITION DIPOLE-MOMENT FOR 249 NM PHOTODISSOCIATION OF ICN

Cyanogen iodide (ICN) has been photodissociated at 249 nm. The CN(X2SIGMA+) photofragments were probed by laser induced fluorescence (LIF) using multiple distinct excitation-detection geometries, allowing the extraction of bipolar moments describing the distribution and mutual correlations of the fragment velocity, angular momentum, and dipole moment vectors. The results of this analysis are consistent with three optically active transitions at this photolysis wavelength, one with parallel character and two with perpendicular character. One of these perpendicular transitions has the direction of the transition dipole moment perpendicular to the plane of the three atoms, whereas the other has the transition moment in the plane of the three atoms, perpendicular to the I-C bond. This picture can be reconciled with recent ab initio calculations of the level structure of the ICN A-X continuum and can also be used as a framework to explain in a consistent manner many of the gross features of the photodissociation dynamics of ICN observed in previous experiments at this wavelength.