Approximate Factorization of Molecular Potential Surfaces II. Internal Rotors

Abstract

Scaling models for the polyatomic potential energy surface occupy a ground intermediate between ab initio surfaces and random matrix models. They are useful for the study of vibrational energy redistribution (IVR) in large molecules, and have been shown to reproduce many features of more accurate spectroscopically fitted or

Vibrational overtone spectroscopy of jet-cooled methanol from 5000 to 14 000 cm−1

“…3,11 Moreover, there is evidence for strong coupling between the three CH fundamentals and the six HCH bend combinations. 17 The spectral region above 5000 cm Ϫ1 contains a large number of vibrational bands that may provide insights into the couplings between the various vibrational modes in methanol. 17 The spectral region above 5000 cm Ϫ1 contains a large number of vibrational bands that may provide insights into the couplings between the various vibrational modes in methanol.…”

The adiabatic approximation as a diagnostic tool for torsion–vibration dynamics

“…Their model calculations were compared to ab initio results on several small molecules. Pearman and Gruebele [10] extended this approach to internal rotor molecules including methanol and hydrogen peroxide and found that the IVR coupling matrix elements fell off less rapidly with coupling order than is typical of rigid molecules. The coupling order is the total number of vibrational quanta created or destroyed when one vibrational state is converted to another.…”

“…LA internal rotation has been shown to accelerate intramolecular vibrational redistribution (IVR) between the LA vibration and the SA vibrations with amplitude on nearby nuclei [5][6][7][8][9]. Pearman and Gruebele [10] have shown that when internal rotation is involved, the scaling behavior of the coupling matrix elements results in a slower fall-off of the coupling strength with coupling order than if only SA vibrations were involved. The result is a larger contribution from direct high-order coupling and, in appropriate circumstances, faster IVR [10,11].…”

“…Pearman and Gruebele [10] have shown that when internal rotation is involved, the scaling behavior of the coupling matrix elements results in a slower fall-off of the coupling strength with coupling order than if only SA vibrations were involved. The result is a larger contribution from direct high-order coupling and, in appropriate circumstances, faster IVR [10,11].…”

Doppler-limited CW infrared cavity ringdown spectroscopy of the ν1+ν3 OH+CH stretch combination band of jet-cooled methanol

“…State-selected IRLAPS spectra of methanol have shown that IVR occurs on multiple timescales [12][13][14][15]. In their studies of the scaling of IVR coupling matrix elements, Pearman and Gruebele [16] have used methanol as a case study to demonstrate how torsionvibration coupling can lead to enhanced IVR.…”