A microwave cavity measurement of collision-induced absorption in N2 and CO2 at 4.6 cm−1

1978 ◽  
Vol 56 (8) ◽  
pp. 1037-1045 ◽  
Author(s):  
I. R. Dagg ◽  
G. E. Reesor ◽  
M. Wong
Keyword(s):  
Far Infrared ◽  
Microwave Cavity ◽  
Induced Absorption ◽  
Microwave Frequencies ◽  
Infrared Measurements ◽  
Cavity Measurement

Microwave cavity measurements have been extended to the 140 GHz or 4.6 cm−1 region. The details of the apparatus and method are presented. The techniques have been applied to the measurement of collision-induced absorption in N2 and CO2 at 295 K. The results are compared with measurements at lower microwave frequencies and also with far infrared measurements.

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.

Collision-induced absorption in ethylene in the microwave and far-infrared regions

1981 ◽  
Vol 59 (1) ◽  
pp. 57-65 ◽  
Author(s):  
I. R. Dagg ◽  
L. A. A. Read ◽  
B. Andrews
Keyword(s):  
Fourier Transform ◽  
Far Infrared ◽  
Microwave Cavity ◽  
Fourier Transform Spectrometer ◽  
Density Range ◽  
Spectral Moments ◽  
Induced Absorption ◽  
Hcn Laser

The collision-induced rotation–translation spectrum of gaseous ethylene has been measured at 295 K over a density range from 3.7 to 23.9 amagat in the 40–360 cm−1 region and at densities up to 50 amagat at 2.3 cm−1 and at 29.6 cm−1. The measurements were made using a Fourier transform spectrometer, an HCN laser, and a microwave cavity technique. Two spectral moments of the observed spectrum have been determined and used in a recently developed theory to provide values for the components of the quadrupole tensor of ethylene: Qxx = −3.54 × 10−26, Qyy = 1.77 × 10−26, Qzz = 1.77 × 10−26 esu. These values are compared with those obtained by other workers using different methods. The z direction is along the C–C axis, the y direction is in the plane of the molecule, and the x axis is perpendicular to the plane of the molecule.

Far-infrared measurements of Holstein processes and low-energyαtr2F(ω)structure inV3Si

1979 ◽  
Vol 19 (11) ◽  
pp. 5689-5693 ◽  
Author(s):  
S. W. McKnight ◽  
S. Perkowitz ◽  
D. B. Tanner ◽  
L. R. Testardi
Keyword(s):  
Far Infrared ◽  
Infrared Measurements

Astronomy on Ice

1986 ◽  
Vol 6 (4) ◽  
pp. 403-415 ◽  
Author(s):  
Martin A. Pomerantz
Keyword(s):  
Gamma Ray ◽  
Far Infrared ◽  
The United States ◽  
High Energy ◽  
Observational Cosmology ◽  
Significant Information ◽  
Infrared Measurements ◽  
Energy Gamma ◽  
Low Humidity ◽  
Scientific Station

AbstractThe geographic South Pole, where the United States maintains a year-round scientific station, affords a number of unique advantages for certain types of astronomical observations. These include: continuous viewing and constant declination of ail objects in the southern celestial hemisphere, exceedingly low humidity, extended periods of coronal seeing, high altitude, and uniform terrain. The areas of research that have already benefited immensely from thèse extraordinary features are helioseismology and submillimeter astronomy. Unparalleled observations of global solar oscillations have already yielded significant information about the structure and dynamics of the Sun’s interior. Far infrared measurements of various galactic and extra-galactic regions have attained an unprecedented level of sensitivity, limited for the first time only by the noise inherent in the detector. In addition to further helioseismological observations, currently planned future activities include observational cosmology and ultra high energy gamma ray astronomy.

scholarly journals Determination of confusion noise for far-infrared measurements

2005 ◽  
Vol 430 (1) ◽  
pp. 343-353 ◽  
Author(s):  
Cs. Kiss ◽  
U. Klaas ◽  
D. Lemke
Keyword(s):  
Far Infrared ◽  
Infrared Measurements

COLLISION-INDUCED ABSORPTION OF COMPRESSED GASES IN THE FAR INFRARED, PART I

1965 ◽  
Vol 43 (5) ◽  
pp. 729-750 ◽  
Author(s):  
D. R. Bosomworth ◽  
H. P. Gush
Keyword(s):  
Fourier Analysis ◽  
Infrared Absorption ◽  
Michelson Interferometer ◽  
Far Infrared ◽  
Gas Mixtures ◽  
Experimental Techniques ◽  
Rare Gas ◽  
Absorption Coefficients ◽  
Induced Absorption ◽  
Separate Paper

A study is being made of the far infrared absorption occurring in compressed rare-gas mixtures, and compressed homonuclear diatomic gases. The region investigated lies between 20 and 400 cm−1. The spectra are obtained from the Fourier analysis of interferograms produced by a dynamic Michelson interferometer. It is possible to obtain accurate absolute absorption coefficients for broad bands using this method provided care is exercised in the analysis of the interferograms. The necessary precautions are discussed in detail. The precision of the method obtained in practice is demonstrated using the far infrared bands of hydrogen and nitrogen as examples. Only the experimental techniques are discussed in this paper; the detailed results follow in a separate paper.

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.

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