Statistical Inhomogeneous Broadening of Infrared and Raman Transitions in Highly Vibrationally Excited XY₆ Molecules

Abstract

Simulations of the spectra of vibrational transitions in highly vibrationally excited XY6 molecules at certain energy E vib are performed. The infrared (IR) transitions in the mode ν3 of the molecules SF6 and WF6 as well as the Raman ones in the mode ν1 of SF6 are studied. The shapes and parameters of the spectral bands, such as the integral intensity, the mean frequency, and the width, are obtained in a wide range of E vib. The calculated widths prove to be much broader than the expected contributions to them because of intramolecular vibrational relaxation (IVR); this indicates the dominant role of statistical inhomogeneous broadening in the width formation for the investigated molecules.

Intramolecular vibrational redistribution: from high-resolution spectra to real-time dynamics

“…References to corresponding experimental papers will be given in Section 5.5. Here, we note that numerical experiments [119] performed for different modes of SF 6 and WF 6 molecules led to the following main conclusions:…”

“…Nevertheless, the limiting case is realistic [118,119] when the spectrum of jg a i 3 jg a H i transitions is similar to the above-described spectrum consisting of lines with frequencies o b and intensities I b . This is the situation (Fig.…”

“…stants of the molecule are known. An example for an SF 6 molecule [119] is demonstrated in Figs 6b±d. The choice of this molecule for studies was not accidental.…”

“…Optical transition can occur from the jg a i state to the jg a H i state having the nonzero projection onto some of the states h . (b±d) Shapes of the inhomogeneous band profile in the quasicontinuum of the SF 6 molecule (Stokes Raman scattering in the n 1 band) calculated for different energies: 7000 (b),15,000 (c), and 30,000 cm À1 (d)[119].…”

Intramolecular Vibrational Dynamics in Free Polyatomic Molecules with C═O Chromophore Bond Excited by Resonant Femtosecond IR Laser Radiation

“…We believe that the magnitude of this constant level is determined by the excess energy in all the modes of the molecule, which is acquired as a result of the redistribution of the absorbed energy. Indeed, intermode anharmonic shifts as a result of an energy increase in modes of the molecule (especially, low-frequency ones) lead to a statistical inhomogeneous broadening of the band (see ref 27) and to its shift as a whole, compared to the shape of the band before the excitation. This broadening gives rise to a stationary signal from heated molecules at the used probe frequencies, including those of lowest transitions.…”