Solvent and temperature dependence of the fermi resonance parameters in methanol

Schwartz, M.; Moradi‐Araghi, A.; Koehler, W.H.

doi:10.1016/0022-2860(82)85337-4

Cited by 23 publications

(23 citation statements)

References 24 publications

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“…For kT << w2 the frequency splitting w+ -w-according to Eqn (19) is given by At exact resonance w I = 2w2 and with no common energy shift w 1 + 2w2 = w+ + w-we obtain w+-w-= d ( w , -2w2)2+ 8 V2 and o, + 20, = o+ + w-are never fulfilled exactly, but the deviations between the expressions (20) and (21) are smaller than or of the order of 1 cm-' for typical values of w 1 and K in molecules. The first-order perturbation treatment, therefore, is numerically sufficient in all practical cases.…”

Section: Discussionmentioning

confidence: 99%

“…However, changes with temperature and/or concentration of frequencies and anharmonicity constants of molecules in ~o l u t i o n~~-~~ are often of the order of a few cm-'. In such cases analysis of experimental data with the help of Eqn (19) is necessary . Equation (19), on the other hand, is exactly equivalent to Eqn (2) if the fundamental w2 is replaced with the overtone 2w2 and if the empirical parameter b of Schwartz and WangI4 is related to the anharmonicity constant by or, with V = 5K (2wl)-1'2(2w2)-1, by b2 = 16 V2wlw2…”

Section: Discussionmentioning

confidence: 99%

“…The resulting expressions (19) for Fermi resonances deviate from both the first-order perturbation expressions (1) and from coupled oscillator model expressions (2) with w2 being replaced by the overtone 20,.…”

Section: (17)mentioning

confidence: 92%

“…After some algebra, one obtains The poles of Eqn (18) are the (approximate) eigenvalues of determinant (1 l), and are given by i $d( w -4w $)' + 64 V2w ,w2( 2 naz + 1) (19) and correspond to sharp peaks in the Raman intensity (14). The Bose factor nn,= ( a l a ; ) = [exp ( w 2 / k T ) -13-'…”

Section: (17)mentioning

confidence: 99%

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Theory of Fermi resonances in Raman and infrared spectra

Monecke

1987

J Raman Spectroscopy

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Fermi resonances are analysed in the literature either by degenerate first-order perturbation theory or by the coupled oscillator model of Schwartz and Wang. Here the perturbation treatment is generalized, taking into account the coupling not only between a fundamental and an overtone, but also with other eigenstates, required by a proper treatment of the Bose character of vibrations. The resulting expressions for the frequency shifts differ from those of both other models. Numerical differences from the first-order perturbation treatment are small in most cases. However, the results can be used to relate the empirical interaction constant of the coupled oscillator model to an actual anharmonicity constant.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: (17)mentioning

confidence: 92%

Section: (17)mentioning

confidence: 99%

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Theory of Fermi resonances in Raman and infrared spectra

Monecke

1987

J Raman Spectroscopy

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“…However, Fermi resonances are not strongly susceptible to temperature because this will implicate a temperature dependence of the anharmonic coupling between the vibrational mode and the overtone/combinational mode. 49 The temperature dependence of the asymmetric stretch mode shows that the ratio of the amplitude of the two bands is temperature dependent, i.e., its ratio changes from 0.2 at 20…”

Section: Discussionmentioning

confidence: 99%

Hydration and vibrational dynamics of betaine (N,N,N-trimethylglycine)

Cui

Mathaga

et al. 2015

The Journal of Chemical Physics

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Zwitterions are naturally occurring molecules that have a positive and a negative charge group in its structure and are of great importance in many areas of science. Here, the vibrational and hydration dynamics of the zwitterionic system betaine (N,N,N-trimethylglycine) is reported. The linear infrared spectrum of aqueous betaine exhibits an asymmetric band in the 1550-1700 cm −1 region of the spectrum. This band is attributed to the carboxylate asymmetric stretch of betaine. The potential of mean force computed from ab initio molecular dynamic simulations confirms that the two observed transitions of the linear spectrum are related to two different betaine conformers present in solution. A model of the experimental data using non-linear response theory agrees very well with a vibrational model comprising of two vibrational transitions. In addition, our modeling shows that spectral parameters such as the slope of the zeroth contour plot and central line slope are both sensitive to the presence of overlapping transitions. The vibrational dynamics of the system reveals an ultrafast decay of the vibrational population relaxation as well as the correlation of frequency-frequency correlation function (FFCF). A decay of ∼0.5 ps is observed for the FFCF correlation time and is attributed to the frequency fluctuations caused by the motions of water molecules in the solvation shell. The comparison of the experimental observations with simulations of the FFCF from ab initio molecular dynamics and a density functional theory frequency map shows a very good agreement corroborating the correct characterization and assignment of the derived parameters. C 2015 AIP Publishing LLC. [http://dx

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