15min:
VIBRONIC SPECTROSCOPY OF JET-COOLED 1,4-PHENYLENE DIISOCYANIDE.

DEEPALI N. MEHTA, ANNA K. GUTBERLET AND TIMOTHY S. ZWIER, Department of Chemistry, Purdue University, West Lafayette, IN 47907.

This talk will present results of a gas phase, jet-cooled vibronic spectroscopy study of 1,4-PDI. A fluorescence excitation spectrum spanning the range 35,500-44,100 cm- 1 (226.5-281.5 nm) has been recorded, as well as a resonant two photon ionization excitation and UV hole-burning spectrum, in the region of 35,500-36,500 cm-1. The S0-S1 origin is a weak band located at 35,566 cm-1. The spectrum in the S1 region is dominated by vibronic coupling to the S2 state. Dispersed fluorescence spectra will be presented that uncover and characterize the vibronic coupling. We have also located the S0-S2 origin 5687 cm-1 above the S0-S1 origin. Evidence will be presented for the coupling of the S2 levels with nearby S1 levels and for internal conversion from S2 to S1 on the timescale of the fluorescence.