Twohyphen;Photon Capture Cross Sections of Pyrene and Benzpyrene from SCFsngbnd;MO Calculations

摘要

The twohyphen;photon capture cross sections for pyrene and 3,4hyphen;benzpyrene are calculated using SCFsngbnd;CI pihyphen;electronic wavefunctions and the theory of Goepperthyphen;Mayer. The cross section is shown to be dependent on the product of the photon flux and a constant, dgr;, which may be calculated from suitable matrix elements and the line shape function. For randomly oriented molecules and polarized light the calculated values of dgr; for pyrene and 3,4hyphen;benzpyrene are, respectively, 260times;10mdash;51and 1500times;10mdash;51cm4middot;sec atommdash;1photonmdash;1. These are to be compared with the experimental values of, respectively, 1times;10mdash;51and 50times;10mdash;51cm4middot;sec atommdash;1middot;photonmdash;1. The effect of molecular symmetry on the twohyphen;photon absorption of polarized light is illustrated for molecules ofD2hsymmetry. For a twohyphen;photon transition to aB1gstate, the maximum probability is shown to lie approximately 45deg; between thexandyaxes of the molecule which are the axes of maximum probability for onehyphen;photon absorption.