Collision-Induced Absorption of H2 and He–A Mixtures near λ = 1 mm

1972 ◽  
Vol 50 (17) ◽  
pp. 2058-2059 ◽  
Author(s):  
S. Cunsolo ◽  
H. P. Gush
Keyword(s):  
Dipole Moment ◽  
Induced Absorption ◽  
Sudden Drop ◽  
Absorption Intensity

The spectrum of compressed H2 and a He–A mixture has been measured from 4 to 50 cm−1. A sudden drop in absorption intensity below 10 cm−1 is attributed to reversal of the dipole moment in successive collisions.

Pressure-induced absorption in nonpolar gases containing tetrahedral molecules

1976 ◽  
Vol 54 (5) ◽  
pp. 611-617 ◽  
Author(s):  
A. D. Buckingham ◽  
A. J. C. Ladd
Keyword(s):  
Dipole Moment ◽  
Field Gradient ◽  
Infrared Radiation ◽  
Far Infrared ◽  
Spectral Moment ◽  
Induced Absorption ◽  
Integrated Intensity ◽  
Tetrahedral Molecules ◽  
Spherical Molecule ◽  
Far Infrared Radiation

The theory of pressure-induced absorption of far infrared radiation by gases is extended to include the contribution of the dipole moment induced in a molecule by the field gradient due to its neighbours. This dipole is nonzero when the molecule lacks a centre of inversion, as in a tetrahedron. In the collision of two tetrahedra, the dipole induced in molecule 2 by the electric field of the octopole moment Ω1 of the partner leads to transitions in which ΔJ(1) = 0, ± 1, ±2, ±3, and ΔJ(2) = 0. The dipole induced by the field gradient of Ω1 leads to ΔJ(1) = 0, ±1, ±2, ±3, and ΔJ(2) = 0, ±1, ±2, ±3, and therefore gives a required increase in absorption at higher frequencies. The field-gradient contribution vanishes in a collision involving a tetrahedral and a spherical molecule. General expressions are given for the field-gradient contributions to the integrated intensity and to the −2 spectral moment.

Lineshapes and dipole moments in collision-induced absorption

1981 ◽  
Vol 59 (10) ◽  
pp. 1544-1554 ◽  
Author(s):  
George Birnbaum ◽  
Michael S. Brown ◽  
Lothar Frommhold
Keyword(s):  
Dipole Moment ◽  
Dipole Moments ◽  
Empirical Models ◽  
Fundamental Theory ◽  
Potential Models ◽  
Induced Absorption ◽  
Induced Dipole ◽  
Substantial Error ◽  
Argon Mixture ◽  
Helium Neon

Wave mechanical lineshapes of collision-induced absorption spectra are computed for binary mixtures of argon with helium, neon, and krypton using theoretical dipole moments as input. Comparison with measured spectra shows satisfactory agreement except for the neon–argon mixture, for which either theory or measurement is seen to be in substantial error. Empirical models of the collision-induced dipole moment which reproduce the experimental spectra more closely than the fundamental theory are also given. Best agreement between computed and experimental lineshapes is obtained when potential models which are accurate in the repulsive region are used.

Moment analysis in collision-induced absorption: Determination of a single parameter empirical model for the induced dipole moment of He-Ar gas mixtures

2021 ◽  
pp. 1-16
Author(s):  
M.S.A. El-Kader ◽  
G. Maroulis
Keyword(s):  
Dipole Moment ◽  
Empirical Model ◽  
Adjustable Parameter ◽  
Classical Physics ◽  
Induced Absorption ◽  
Induced Dipole ◽  
Absorption Determination ◽  
Ar Gas ◽  
Good Agreement

We present a method for the construction of a one-adjustable-parameter empirical model for the induced dipole moment. The method is based on classical physics principles and relies on the first three spectral moments of the collision-induced absorption spectra at various temperatures and new interaction potentials. In this work it is applied to the spectra of He-Ar mixtures. Our values are in good agreement with the available ab initio data. The profiles calculated with these models at various temperatures are in excellent agreement with experiment.

Thermally induced absorption-intensity transfer betweenTl+bands in alkali halides

1977 ◽  
Vol 15 (12) ◽  
pp. 5983-5990
Author(s):  
U. Giorgianni ◽  
G. Mondio ◽  
P. Perillo ◽  
G. Saitta ◽  
G. Vermiglio
Keyword(s):  
Alkali Halides ◽  
Induced Absorption ◽  
Thermally Induced ◽  
Absorption Intensity ◽  
Intensity Transfer

Theory of Intercollisional Interference Effects. IV. Does a Zero Minimum in Induced Absorption Imply the Proportionality of the Induced Dipole Moment to the Force?

1973 ◽  
Vol 51 (23) ◽  
pp. 2455-2458 ◽  
Author(s):  
J. Courtenay Lewis
Keyword(s):  
Dipole Moment ◽  
Lorentz Gas ◽  
Intermolecular Force ◽  
Interference Effects ◽  
Induced Absorption ◽  
Induced Dipole ◽  
Interference Minimum

We show that, within the limits of the theory of intercollisional interference effects developed for collision-induced absorption by a Lorentz gas in paper I of this series, an intercollisional interference minimum which goes precisely to zero implies that the induced dipole moment is exactly proportional to the intermolecular force.

COLLISION-INDUCED ABSORPTION OF SUBMILLIMETER RADIATION BY NON-POLAR ATMOSPHERIC GASES

1962 ◽  
Vol 40 (1) ◽  
pp. 122-127 ◽  
Author(s):  
R. Heastie ◽  
D. H. Martin
Keyword(s):  
Dipole Moment ◽  
Energy Balance ◽  
Hydrogen Gas ◽  
Spectroscopic Techniques ◽  
Atmospheric Gases ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Induced Absorption ◽  
Significant Attenuation ◽  
Infrared Frequencies

The recent development of spectroscopic techniques for extreme infrared frequencies, below 100 cm−1, has enabled us to observe collision-induced absorption in non-polar gases, viz. oxygen, nitrogen, air, and helium–argon mixtures. This absorption results from the modulation of the distortion dipole moment of each pair of colliding molecules by their rotational and translational motions. It is of the kind observed previously at higher frequencies by Kiss, Gush, and Welsh using hydrogen gas. By making measurements at pressures up to 120 atmospheres, the absorption coefficients have been determined over the frequency range 30–100 cm−1.Attention is drawn to the possibilities that such processes may play a role in atmospheric energy balance and might give rise to significant attenuation if beams of infrared radiation were used for communications.

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