MULTILEVEL VIBRATIONAL DEPHASING AND VIBRATIONAL ANHARMONICITY FROM INFRARED PHOTON-ECHO BEATS

Vibrational photon echo experiments were performed on the asymmetric C O stretching mode of tungsten hexacarbonyl in glassy dibutylphthalate as a function of temperature using sub-picosecond infrared pulses (197 6 cm(-1)) from a flee electron laser. The echo decays display pronounc ed beats and are bi-exponential. The beats and bi-exponential decays a rise because the bandwidth of the pulses exceed the vibrational anharm onicity, leading to the excitation and dephasing of a multilevel coher ence. From the beat frequency, the anharmonicity is determined to be 1 4.7 cm(-1). From the bi-exponential decay components, the temperature- dependent vibrational dephasing of both the upsilon = 0 --> 1 and upsi lon = 1 --> 2 transitions are determined.