LASER-INDUCED SINGLE VIBRONIC LEVEL FLUORESCENCE SPECTRA OF PROPYNAL VAPOR

Author Institution: Department of Chemistry, U. of Arizona; Department of Physics, U. of Georgia; Department of Chemistry, Davidson CollegeSingle vibrational levels (SVLs) in the $S_{1}$ state of propynal vapor have been populated by tuned, pulsed laser excitation in room temperature ``bulb” experiment. Time-resolved fluorescence spectra for the origin level, five SVLs corresponding to a single quantum of one mode, and two combination SVLs have been recorded and assigned. Mode 4 has the greatest spectral activity and displays an anharmonicity of $X_{e} = .00594 cm^{-1}$ in the ground state. Spectral evidence supports the activity of all modes except mode 1. After mode 4, the most prominent vibrational modes in the origin spectrum are 9 and 12, which contrasts with the prominence of modes 5, 6 and 10 and relative unimportance of modes 9 and 12 in the absorption spectrum. As expected, it is found that the same transitions which occur in the origin spectrum are observed in all other spectra. The spectral structure in all spectra consists of (1) fundamentals or overtones of single modes, (2) fundamentals or overtones of single modes in combination with a $4_{n}^{0}$ progression member, $4_{n}^{0} X_{m}^{0}$ or (3) fundamentals or overtones of two modes in combination with a $4_{n}^{0}$ progression member