The quadrupole moment of acetylene from collision-induced absorption in a gaseous mixture with argon

1988 ◽  
Vol 66 (5) ◽  
pp. 453-459 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
W. Smith ◽  
M. Missio ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Quadrupole Moment ◽  
Line Shape ◽  
Theoretical Estimate ◽  
Gaseous Mixture ◽  
Experimental Spectrum ◽  
Laser Source ◽  
Shape Theory ◽  
Frequency Range ◽  
A Value ◽  
Theoretical Line

The collision-induced spectrum of a mixture of argon and acetylene (100:1) is reported in the frequency range below 240 cm−1. The spectrum is obtained from the total absorption in the mixture at pressures up to 1400 psi (1 psi = 6.89 kPa) and subtraction of the contribution from an allowed difference band of pure acetylene centred near 113 cm−1. The measurements are made with a Michelson Fourier-transform interferometer and with a laser source at 84.1 cm−1. The quadrupole moment of acetylene determined from the experimental spectrum and existing theory for the integrated absorption coefficient is 5.42 (± 0.41) B if a theoretical estimate of the hexadecapole moment is used. Alternatively, a value of 6.14 (± 0.46) B is obtained if the contribution from the hexadecapole moment is assumed to be zero. An extension of the line-shape theory, 1T6, that includes the contribution from hexadecapolar induction is also reported. The resulting theoretical line shape is compared with the experimental spectrum.

The quadrupole moment of cyanogen: a comparative study of collision-induced absorption in gaseous C2N2, CO2, and mixtures with argon

1986 ◽  
Vol 64 (11) ◽  
pp. 1475-1481 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Quadrupole Moment ◽  
Spectral Region ◽  
Gaseous Mixture ◽  
Far Infrared ◽  
Spectral Moments ◽  
A Value ◽  
Large Anisotropy ◽  
Experimental Values ◽  
Microwave Techniques ◽  
Good Agreement

The collision-induced spectra of C2N2 gas and a gaseous mixture of C2N2 and Ar at 298 K have been obtained in the spectral region below 120 cm−1 using far-infrared laser and microwave techniques as well as a Fourier-transform spectrometer. In addition, the collision-induced spectra of a gaseous mixture of CO2 and Ar are reported at temperatures of 233 and 298 K in the spectral region below 230 cm−1. The theoretical values for the spectral moments α1 and γ1 for CO2 are much smaller than the experimental values, as expected for a molecule with a relatively large quadrupole moment. However, for CO2–Ar mixtures, the agreement between the theoretically and experimentally determined spectral moments is relatively good, resulting in a value of 4.6 B for the quadrupole moment of CO2 instead of the generally accepted value of 4.3 B. The quadrupole moment of C2N2 is estimated to be 6.2 ± 0.4 B from our data and the theory for the spectral moments, if a correction is made for an overestimate of the quadrupole moment similar to that obtained for the CO2–Ar mixture. This value is considerably smaller than a previously reported calculated result of 9.0 B. Line-shape expressions based on information theory (IT6) do not yield good agreement with experiment, a result that is attributed to the large anisotropy of the molecules.

Far infrared absorption in gaseous CCl4 and CS2

1989 ◽  
Vol 67 (5) ◽  
pp. 507-514 ◽  
Author(s):  
I. R. Dagg ◽  
M. Missio ◽  
A. Anderson ◽  
W. Smith ◽  
L. A. A. Read
Keyword(s):  
Quadrupole Moment ◽  
Absorption Spectra ◽  
Infrared Absorption ◽  
Theoretical Estimate ◽  
Gaseous Mixture ◽  
Far Infrared ◽  
Frequency Region

The absorption spectra of gaseous CS2, CCl4, and a gaseous mixture of CCl4 and argon at temperatures up to 400 K in the frequency region below 140 cm−1 are reported. From the results on CCl4, the octupole moment is estimated to be 16 ± 3.0 × 10−34 esu; the hexadecapole moment, 64 ± 12 × 10−42 esu. For CS2, if a previously measured value of 3.6 B for the quadrupole moment is assumed, the hexadecapole moment is estimated to be less that 24 × 10−42 esu, considerably less than an earlier theoretical estimate.

Line-shape theory of magnetoabsorption in semiconductor superlattices

1989 ◽  
Vol 40 (8) ◽  
pp. 5497-5506 ◽  
Author(s):  
Hanyou Chu ◽  
Yia-Chung Chang
Keyword(s):  
Line Shape ◽  
Shape Theory ◽  
Semiconductor Superlattices

Collision-induced absorption in nitrogen at low temperatures

1985 ◽  
Vol 63 (5) ◽  
pp. 625-631 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
L. A. A. Read
Keyword(s):  
Quadrupole Moment ◽  
Laser System ◽  
Far Infrared ◽  
Microwave Cavity ◽  
Jones Potential ◽  
Induced Absorption ◽  
Line Shapes ◽  
Theoretical Predictions ◽  
Theoretical Line

The collision-induced absorption (CIA) spectrum for nitrogen has been measured in the spectral region below 360 cm−1 at 126, 149, 179, and 212 K. The measurements have been obtained using Fourier transform infrared (FTIR) techniques, a far infrared (FIR) laser system operating at 84.2 and 15.1 cm−1, and microwave cavity techniques. The experimental line shapes have been compared with the theoretical predictions of Joslin, based on Mori theory, and of Joslin and Gray, based on information theory alone. The data have been used to determine the quadrupole moment employing various intermolecular potentials. One Lennard–Jones potential has resulted in a quadrupole moment of 1.51 B, the value that was used in generating the theoretical line shapes. These results, when combined with our forthcoming measurements on nitrogen mixed with methane and argon, may be helpful in determining the role of CIA in calculating the opacity of some planetary atmospheres.

A STUDY OF METHODS FOR OBTAINING HIGH RESOLUTION WITH A PAIR SPECTROMETER

1960 ◽  
Vol 38 (2) ◽  
pp. 194-216 ◽  
Author(s):  
G. A. Bartholomew ◽  
P. J. Campion ◽  
K. Robinson
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Line Shape ◽  
Theoretical Line

Methods of improving the resolution and line shape of a flat magnetic field pair spectrometer with the aid of specially designed detector apertures are described. The performance of two such apertures is described in detail. The theoretical line shape and resolution for one type of aperture are calculated and compared with experiment.

In-plane lattice-parameter and crystallite-size determination in a turbostratic graphite-like structure

1994 ◽  
Vol 27 (5) ◽  
pp. 767-771 ◽  
Author(s):  
Yu. G. Andreev ◽  
T. Lunström
Keyword(s):  
Crystallite Size ◽  
Line Shape ◽  
Lattice Parameter ◽  
Size Determination ◽  
Instrumental Function ◽  
Boron Nitrides ◽  
Plane Lattice ◽  
Profile Fitting ◽  
Theoretical Line ◽  
Diffraction Peaks

A detailed recipe is given for the refinement of in-plane lattice-parameter and crystallite-size values of a turbostratic graphite-like structure through the profile fitting of the diffraction peaks from random layers. Folding of the theoretical line shape with the experimentally measured instrumental function provides convenient correction for systematic broadening. The devised technique is applied to the analysis of turbostratic hexagonal boron nitrides.

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