15min:

BROOKS H. PATE, DAVID GREEN, REBECCA HOLMBERG, EVAN HUDSPETH AND DAVID A. MCWHORTER, Department of Chemistry, University of Virginia, Charlottesville, VA 22901.

The microwave spectra of single molecular eigenstates of propargyl alcohol (HCCCH₂OH) in the region of the acetylenic C-H stretch are presented. Single eigenstates resulting from extensive intramolecular vibrational mixing are accessed through the high resolution (5 MHz) infrared spectrum measured using an electric-resonance optothermal molecular beam spectrometer. Various infrared-microwave double-resonance and infrared-microwave-microwave triple-resonance spectroscopy techniques are used to measure the "rotational" spectra of the highly mixed molecular eigenstates. These "rotational" spectra are characterized by a narrow frequency width. The width of the rotational spectrum is much less than the width observed in the single-photon infrared spectrum which results from rapid intramolecular vibrational energy redistribution (IVR). The rotational spectrum of molecular eigenstates in the range of J=0-4 and K_a= 0-2 are investigated. The narrow width of the rotational spectrum of a highly vibrationally excited molecule is explained in terms of the exchange narrowing formalism developed for NMR spectroscopy.