A DIRECT DETERMINATION OF THE DIRECTION FOR THE TRANSITION DIPOLE-MOMENT BY THE POLARIZED LASER PHOTOLYSIS OF THE ORIENTED CH3I BEAM

A beam-intensity-depletion (BID) method to determine the direction of the transition dipole moment in the molecular frame was demonstrated i n the polarized laser photolysis of the oriented CH3I beam. The deplet ion of the primary beam intensity of oriented CH3I via the photodissoc iation with linearly polarized laser light was measured as a function of molecular orientation and the polarization angle of the polarized l aser light. The (X-A) transition of CH3I in the \111] rotational state was probed with linearly polarized laser light at 248 nm. The orienta tional dependence of the BID indicates that this transition is predomi nantly (96 +/- 4%) a parallel-type transition at this wavelength. This result is in good agreement with the previous result deduced by the a ngular distribution of the photofragment, showing the usefulness of th is direct method.