Multilevel vibrational dephasing and vibrational anharmonicity from infrared photon echo beats

Abstract

Vibrational photon echo experiments were performed on the asymmetric CO stretching mode of tungsten hexacarbonyl in glassy dibutylphthalate as a function of temperature using sub-picosecond infrared pulses (1976 cm −1) from a free electron laser. The echo decays display pronounced beats and are bi-exponential. The beats and bi-exponential decays arise because the bandwith of the pulses exceed the vibrational anharmonicity, leading to the excitation and dephasing of a multilevel coherence. From the beat frequency, the anharmonicity is determined to be 14.7 cm −1. From the bi-exponential decay components, the temperature-dependent vibrational dephasing of both the v = 0 → 1 and v = 1 → 2 transitions are determined.