## Abstract

The collective polarizability anisotropy dynamics of liquid methyl iodide at room temperature and ambient pressure was studied by using optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES) with 45 fs laser pulses. The OHD-RIKES data are analyzed by using both the model-dependent approach, which assumes four distinct temporal responses, and the model-independent Fourier transform approach, which generates a spectral density. Near zero time, the OHD-RIKES transient is dominated by the instantaneous electronic response. The short-time nuclear response is characterized by two components. The first component is interpreted as arising from an inhomogeneously broadened (fwhm ≈ 62 cm^{-1}) underdamped intermolecular vibrational mode with a mean frequency of ∼60 cm^{-1}. The second component is an intermediate quasi-exponential response with a 1/e time constant of ∼200 fs. At longer times, the OHD-RIKES transient decays exponentially with a 1/e time constant of 1.76 ± 0.05 ps, which corresponds to the collective reorientation time of CH_{3}I. The spectral density peaks at ∼24 cm^{-1} and has a fwhm of ∼80 cm^{-1}. The spectral density can be well fitted by an ohmic distribution function with ω_{c} ≈ 30 cm^{-1}. The spectral density obtained from the OHD-RIKES data is consistent with previously measured depolarized Rayleigh scattering and low-frequency far infrared absorption spectra for liquid CH_{3}I.

Original language | English |
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Journal | Journal of physical chemistry |

Volume | 100 |

Issue number | 24 |

DOIs | |

State | Published - Jun 13 1996 |