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Comparison of infrared absorption intensities of benzene in the liquid and gas phases (1994)

Bertie, John E. ; Keefe, C. Dale

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 101 (1994), S. 4610-4616

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: This paper presents a comparison of the absolute infrared absorption intensities in the liquid and gas phases for the four infrared active fundamentals of benzene. In Herzberg's notation these are ν12 (∼3070 cm−1), and ν4 (∼675 cm−1). Published data are used, including the recently published spectra of liquid benzene that have been accepted by the International Union of Pure and Applied Chemistry as secondary intensity standards. The present results agree qualitatively with the conclusions drawn in 1970 that the intensity Aj of ν12 is much smaller for the liquid than for the gas, and those of ν13, ν14, and ν4 are all larger for the liquid. The inclusion of measurements made since 1970 should make the quantitative results reported here the most reliable. However, two quite different values have been reported in the 1980's for the intensity of ν14 in the gas phase, and both are considered. The comparison for ν14 is also complicated by the existence of weak bands in the spectrum of the liquid that are not observed in that of the gas. It is noted in this work that the traditional comparison, of the areas under the molar absorption coefficient spectra, Aj, for the gas and liquid through the Polo–Wilson equation, has the drawback that the ratio expected if the dipole moment derivative is unchanged is different for each band as well as for each liquid.A much more convenient ratio, that equals unity for all bands of all liquids under the traditional assumptions, is proposed through the imaginary molar polarizability spectrum of the liquid. The magnitudes of the transition moments and the dipole moment derivatives with respect to the normal coordinates under the double harmonic approximation are calculated from the measured intensities for the gas and liquid phases. It is found that the dipole moment derivative of ν12 is 24% smaller in the liquid than in the gas and that of ν13 is 18% larger. The dipole moment derivative of ν4 is unchanged by condensation. The change in the dipole moment derivative of ν14 is not clear, because of the uncertainty in the gas phase intensity and because of the uncertain origin of the intensity of the additional bands in the liquid.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.467448

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Infrared intensities of liquids XXII: Optical and dielectric constants, molar polarizabilities, and integrated intensities of liquid benzene-d6 at 25 °C between 5000 and 450 cm–1 (1998)

Bertie, J. E. ; Keefe, C. Dale

Springer

Fresenius' journal of analytical chemistry 362 (1998), S. 91-108

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ISSN: 1432-1130

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract This paper presents accurate infrared absorption intensities of liquid benzene-d6 at 25 °C, between 5000 and 450 cm–1. The results are presented as graphs and tables of the real, n, and imaginary, k, refractive index spectra, which are also called the optical constant spectra. The real refractive index is shown between 8000 and 450 cm–1. The absolute errors in the k values are estimated to be ∼3% below, and up to 60%, above, 4700 cm–1, with those in the n values ∼0.25% throughout. The Beer-Lambert molar absorption coefficient spectra, E m(˜ν), and the complex dielectric constant spectra, ɛ′(˜ν) and ɛ″(˜ν), were calculated from the optical constant spectra. To correct for macroscopic dielectric effects, the complex molar polarizability spectra, α′m(˜ν) and α″m(˜ν), were calculated from the dielectric constant spectra under the Lorentz local field. The properties of bands in these different spectra are compared. The imaginary molar polarizability spectra were fitted convincingly to 208 Classical Damped Harmonic Oscillator bands, and the areas under the corresponding ˜να″m bands gave the integrated intensities C j . These were assigned as far as possible and are tabulated. The transition dipole moments of well assigned transitions, and for the infrared-active fundamentals, under the double harmonic approximation, the dipole moment derivatives with respect to the normal coordinates, were calculated from the values of C j , and are presented. This appears to be the first extensive measurement of the infrared absorption intensities of liquid benzene-d6. The results are compared with literature data for liquid and gaseous benzene-d6.