POLARIZED FLUORESCENCE OF COMPLEX-MOLECULES COOLED IN A JET - ROTATIONAL-EXCITATION SELECTIVITY IN THE MODEL OF A RIGID TOP

The model of a complex molecule as a rigid asymmetric top is used to a nalyze the mechanism of formation of polarized fluorescence excitation spectra within the rotational profile of a vibronic line owing to the dependence of the emission anisotropy for a separate molecular top on the character of its rotation and the selection produced at every fre quency of the profile by excitation of a specific spectrum of rotation al states of a top. It is shown that the sharpest changes in polarizat ion with frequency are observed at the central region of the profile. Two coexisting stereodynamic isomeric forms of rotation of molecular a symmetric tops are found to make different quantitative and qualitativ e contributions to fluorescence polarization. It is noted that the pol arization dependence may show serial features. The calculated polarize d fluorescence excitation spectra are compared with the experimental s pectra.