A STATISTICAL APPROACH TO THE ANALYSIS OF INFRARED BAND PROFILES

A method is described for the quantitative description of the profile and asymmetry of an infrared absorption band, based on the computation of the second and third incomplete moments of the absorbance curve. Provision is included for differentiation between the intrinsic band asymmetry and that induced by instrumental factors dependent on the direction of scan. A program has been prepared for an I.B.M. 1620 computer to facilitate the calculation of the moments. This program also yields the incomplete fourth moments, the statistical kurtosis parameter ([Formula: see text]), and the Gauss–Cauchy index, though these quantities are not employed in the present investigation. Examples are given of the application of these computations to the analysis of the effect of the spectral slit width on the profiles of bands at 812.7 and 726.6 cm−1 respectively in the spectra of carbon disulphide solutions of perylene and anthracene, and of the effect of the amplifier time constant on the asymmetry of the band at 2234.4 cm−1 in the spectrum of p-chlorobenzonitrile in tetrachloroethylene solution.

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ANALYSIS OF THE PROFILE OF THE FUNDAMENTAL INFRARED BAND OF HYDROGEN IN PRESSURE-INDUCED ABSORPTION

Canadian Journal of Physics ◽

10.1139/p64-082 ◽

1964 ◽

Vol 42 (5) ◽

pp. 873-885 ◽

Cited By ~ 32

Author(s):

J. L. Hunt ◽

H. L. Welsh

Keyword(s):

Absorption Band ◽

Infrared Absorption ◽

Line Shape ◽

Computational Procedure ◽

Pure Hydrogen ◽

Square Root ◽

Infrared Band ◽

Integrated Intensities ◽

Boltzmann Law ◽

Dispersion Line

The pressure-induced fundamental infrared absorption band of hydrogen was measured for a series of pressures in the pure gas and in a H2–He mixture at 300 °K, 195 °K, and 78 °K, and in H2–A and H2–N2 mixtures at 300 °K. The band profiles were separated by a computational procedure into QP and QR (overlap) components and QQ and S(J) (quadrupole) components using a dispersion line shape modified by the Boltzmann law. The dispersion half-width obtained for the overlap components was about twice as great as for the quadrupole components; both half-widths varied as the square root of the temperature. The S(J) lines in pure hydrogen consisted of single and double transitions, the relative intensities of which were in accordance with the assumption of quadrupole interaction. Ortho–para ratios of 3:1 and 1:1 were used in the experiments; the integrated intensities of the band showed very little dependence on the ortho–para ratio, in disagreement with a previously reported result.

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Two types of localized excess electrons in crystalline D2O ice

Canadian Journal of Chemistry ◽

10.1139/v77-326 ◽

1977 ◽

Vol 55 (12) ◽

pp. 2385-2395 ◽

Cited By ~ 40

Author(s):

George V. Buxton ◽

Hugh A. Gillis ◽

Norman V. Klassen

Keyword(s):

Absorption Band ◽

Infrared Absorption ◽

Low Temperatures ◽

Total Yield ◽

Equilibrium Concentration ◽

Electron Trap ◽

Decay Kinetics ◽

Infrared Band ◽

Visible Absorption ◽

Perfect Lattice

In a pulse radiolysis study of crystalline D2O ice, an intense infrared absorption band with λmax > 2350 nm has been found at low temperatures, in addition to the well-known visible absorption band of the trapped electron. The infrared band is also attributed to trapped electrons, partly because of its similarity to the electron absorption band found recently in some D2O glasses at low temperatures. The effects of temperature, dose per pulse, accumulated dose, and added NH4F, HF, and ND3 on the yields and decay kinetics of both bands have been investigated. It is concluded that the electron trap giving rise to the visible band is a vacancy which at low temperatures is radiation-produced by a two-step spur process. At temperatures close to the melting point the vacancy-trap probably exists before the radiation pulse at equilibrium concentration. The electron trap which gives rise to the infrared band is thought to be a cavity that occurs naturally in the perfect lattice. For previously unirradiated samples the infrared band decays by a second order process which is remarkably fast [Formula: see text] The decay reaction is probably neutralization by D2O+. Doping with NH4F increases the yield of the infrared absorption and greatly decreases its decay rate. The total yield of localized electrons in irradiated crystalline D2O is higher than has been generally recognized.

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Pressure Narrowing of the Rotational Lines of the Fundamental Infrared Band of H2 in Collision-Induced Absorption

Canadian Journal of Physics ◽

10.1139/p71-045 ◽

1971 ◽

Vol 49 (3) ◽

pp. 381-384 ◽

Cited By ~ 16

Author(s):

J. De Remigis ◽

J. W. Mactaggart ◽

H. L. Welsh

Keyword(s):

Absorption Band ◽

Infrared Absorption ◽

Half Width ◽

Density Range ◽

Infrared Band ◽

Induced Absorption ◽

Infrared Absorption Band

The enhancement by argon of the pressure-induced fundamental infrared absorption band of hydrogen is studied for Ar densities in the range 8–820 amagat at 152 K. The half-width, Δv1/2, of the quadrupole-induced S1(1) transition remains constant at 55 cm−1 up to ~300 amagat and then decreases to 25 cm−1 at the highest density. In the higher density range Δv1/2 varies inversely as the density. The S1(1) line of H2 in liquid H2–Ar solutions shows a similar pressure narrowing for Ar densities in the range 640–833 amagat at 115 K.

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The Absolute Intensity of the ν4 Infrared Absorption Band of Methane and Its Enhancement by Nitrogen at High Pressures

The Journal of Chemical Physics ◽

10.1063/1.1700233 ◽

1952 ◽

Vol 20 (10) ◽

pp. 1646-1647 ◽

Cited By ~ 19

Author(s):

H. L. Welsh ◽

P. J. Sandiford

Keyword(s):

Absorption Band ◽

Infrared Absorption ◽

High Pressures ◽

Absolute Intensity ◽

Infrared Absorption Band ◽

The Absolute

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THE ABSOLUTE INFRARED ABSORPTION BAND INTENSITIES OF THE METHYLENE GROUP VIBRATIONS OF SOME METHYLENE HALIDES

10.2172/4382317 ◽

1955 ◽

Author(s):

R. Hedges ◽

H. Shull

Keyword(s):

Absorption Band ◽

Infrared Absorption ◽

Infrared Absorption Band ◽

The Absolute ◽

Methylene Group

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Infrared Spectra of the Ices at ≈4 K and the Interpretation of the v OD(D2O) Bands of Ices II and IX

Journal of Glaciology ◽

10.1017/s0022143000033827 ◽

1978 ◽

Vol 21 (85) ◽

pp. 694

Author(s):

F. E. Bates ◽

S. M. Jacobs ◽

J. E. Bertie

Keyword(s):

Infrared Absorption ◽

Far Infrared ◽

Fermi Resonance ◽

Chemical Physics ◽

Vibrational States ◽

Infrared Band ◽

Stretching Vibrations ◽

First Time ◽

Lattice Modes ◽

Complete Interpretation

Abstract We have studied the infrared absorption by the OD stretching, v OD(D2O), and D2O rotational, v R(D2O), vibrations of fully deuterated ice II and ice IX at lo K, and the absorption by OD stretching vibrations, v OD (HDO), of HDO molecules isolated in ices Ih, II, and IX at 10 K. Calculations of the frequencies and relative intensities of the zero-wave-vector normal v OD(D2O) vibrations of ices II and IX have allowed the v OD(D2O) absorption to be assigned. Each component of the band is broad, even at 10 K, most probably because of Fermi resonance between the fundamental OD stretching vibrational states and the isoenergetic continuum of high-order overtone and combination states of the lattice modes. This work has yielded the most complete interpretation yet achieved of an infrared band due to the OH or OD stretching vibrations of a phase of ice. The far-infrared absorption by the translational vibrations of H2O and D2O ices Ih and Ic at 4.3 K has been measured, and has revealed differences between the spectra of ices III and Ic for the first time. Papers describing this work in full have been published in Journal of Chemical Physics, Vol. 67, No. 4, 1977, p. 1311-18, and Vol. 67, No. 6, 1977, p. 2445-48.

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