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The effect of intermolecular interactions on the isotope structures of the Raman bands of CHCl₃, CCl₃F and CCl₃CN

H J Clase and H W Kroto, Mol Phys, 15 pages, 167-172 (1968).

Abstract

The Raman spectra of chloroform, trichloromethyl fluoride and trichloromethyl cyanide have been studied as pure liquids and as solutions in various solvents. In particular, the isotope patterns of those a₁ modes which involve mainly chlorine vibrations have been studied as a function of concentration in cyclopentane.

In certain bands of the pure liquids where the isotope structure is well resolved, this structure is not consistent with species containing three equivalent chlorine atoms.

Pure CFCl₃ possesses bands which exhibit both this anomalous pattern and the expected pattern.

On dilution in a wide range of solvents the anomalous bands revert to the expected pattern and the normal bands are unaffected. The anomalous patterns observed and the behaviours on dilution were identical for all three compounds.

This evidence has been interpreted on the basis of association in the pure liquids though the specific nature of the interactions involved depends on the compound.

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Theory of the effect of intermolecular interactions on the Raman spectra of liquid CHCl₃ and CFCl₃

H W Kroto and J J C Teixeira Dias, Molecular Physics. 06/1970; 18(6).

Abstract

A theory of weak, intermolecular interactions is presented which indicates how association in the liquid state can manifest itself in vibration spectra. The theory is applied in this case to CHCl₃ and CFCl₃.

The calculations predict which bands are most sensitive to the effects of intermolecular interaction. Previous experimental observations on the behaviour of the a₁ vibrations of these molecules are reproduced.

The calculations also predicted new features in the behaviour of the degenerate vibrations which were confirmed experimentally.

The method lends itself to the study of solvent effects on vibration spectra in general.

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The effects of intermolecular interaction in the Raman spectrum of liquid CS₂

H W Kroto and J J C Teixeira Dias

Abstract

The effects of intermolecular interaction in the Raman spectrum of liquid CS₂ have been studied. The anomalous intensity variations observed on dilution are shown to be consistent with previous conclusions.

These were reached as a result of a Force Field Perturbation analysis of intermolecular interactions in the halomethanes. It appears that in general, intermolecular interactions affect bands involving degenerate vibrations particularly strongly.

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Effect of intermolecular interactions on line shapes and depolarisation factors of highly polarised Raman lines

H W Kroto and Y-H Pao, Journal of the Optical Society of America, Vol. 58 pp. 479-483 (1968).

Abstract

The depolarization ratios and line shapes of the Raman lines of benzene and carbon tetrachloride at 992 and 458 cm ^-1, respectively, have been measured in detail both in the pure-liquid state and in solvents such as cyclohexane and acetone.

The lines are narrower in cyclohexane than in the pure-liquid state and all the results can be understood in terms of intermolecular interactions.

We have also shown that the depolarisation ratio of the benzene 992 cm ^-1 line is not constant over the line.