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QUAN JU, CHARLES S. PARMENTER, Department of Chemistry, Indiana University, Bloomington IN 47405.
Cold jet S1 <- S0 rotational band contours have been obtained at 0.3 cm-1 resolution for the p-difluorobenzene-N2 (pDFB-N2) van der Waals complex and analyzed with an asymmetric top simulation program. Satisfactory simulation is possible only if it is assumed that the in-plane electronic transition moment of pDFB-N2 rotates about 37o towards the F-F axis from its position normal to that axis in free pDFB. The vdW bond distances from the ring plane to the N2 bond parallel to that plane are 3.47Å and 3.42Å in the S1 and S0 states, respectively. Several transitions involving the internal rotation of N2 about an axis perpendicular to the ring plane have been assigned. The band positions are consistent with two-fold rotational barriers of 14.0 cm-1 and 19.0 cm-1 for the S0 and S1 states, respectively. These barriers are in agreement with those recently determined from the assignments of different internal rotor transitions seen in the R2PI spectra.