Photofragment angular momentum polarization in the photolysis of symmetric top molecules: Production, detection, and rotational depolarization

We present the fully quantum mechanical distribution of the photofragment angular momentum polarization in the photolysis of an isotropic ensemble of symmetric top molecules. The distribution is written in terms of the recently established anisotropy transforming coefficients cKkdqk (P.S. Shternin, O.S. Vasyutinskii, Chem. Phys. 128 (2008) 194314) which contain all dynamical information on the photolysis dynamics and can be either determined from experiment, or calculated from theory. Explicit expressions for the coefficients cKkdqk for the case of photolysis of symmetric top molecules were obtained within the full quantum mechanical approach and then simplified using the quasiclassical approximation in the high-J limit. The role of the photofragment angular momentum depolarization due to molecular rotation was analyzed for three important particular cases: photolysis of diatomic molecules, photolysis of symmetric top molecules when the angular momentum polarization of atomic photofragments are detected, photolysis of symmetric top molecules when the angular momentum polarization of molecular photofragments are detected. The obtained rotation factors were compared with the results of previous studies. The paper also presents a compact spherical tensor expression for the 2 + 1 REMPI absorption signal which can be used for direct determination of the coefficients cKkdqk from experiment. A comparison was made between the anisotropy transforming coefficients cKkdqk and the polarization parameters A K q introduced very recently by (T.P. Rakitzis, A.J. Alexander, J. Chem. Phys. 132 (2010) 224310) for description of the photofragment polarization in photolysis of polyatomic molecules. This comparison shows that these two sets of parameters are equivalent to each other as they just proportional to each other