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.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

Improved Rotational Constants and Dipole Moment and a Nuclear Quadrupole Coupling Analysis of 2-Cyanothiophene and Dipole Moment of 2-Cyanofurane

1977 ◽  
Vol 32 (2) ◽  
pp. 152-155 ◽  
Author(s):  
J. Wiese ◽  
L. Engelbrecht ◽  
H. Dreizler
Keyword(s):  
Dipole Moment ◽  
Stark Effect ◽  
Dipole Moments ◽  
Quadrupole Coupling Constant ◽  
Rotational Constant ◽  
Coupling Constant ◽  
Frequency Range ◽  
Effect Analysis ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Results of a microwave investigation of the molecules 2-Cyanothiophene and 2-Cyanofurane are reported. The microwave spectrum of 2-Cyanothiophene was examined in the frequency range of 13 -40 GHz mainly to get a more accurate rotational constant A from the assignment of μb-btransitions. From the resolved hyperfine structure due to nuclear quadrupole coupling of the 14N-nucleus the quadrupole coupling constant X+=Xbb + Xcc was determined for 2-Cyanothiophene. No information for X- was available from the measured transitions.From Stark effect studies the dipole moments were determined for both molecules. The nuclear quadrupole coupling as a perturbation of the second order Stark effect was included in the Stark effect analysis

Adiabatische Korrektur der Born-Oppenheimer-Näherung beim GeS und GeSe / Adiabatic Correction of the Born-Oppenheimer Approximation for GeS and GeSe

1976 ◽  
Vol 31 (3-4) ◽  
pp. 374-380 ◽  
Author(s):  
W. U. Stieda ◽  
E. Tiemann ◽  
T. Törring ◽  
J. Hoeft
Keyword(s):  
Dipole Moment ◽  
High Precision ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Rotational Constant ◽  
Frequency Range ◽  
Rotational Spectra ◽  
Oppenheimer Approximation

Abstract The rotational spectra of GeS and GeSe were measured in the frequency range of 66 GHz to 110 GHz with high precision. The breakdown of the Born-Oppenheimer approximation was observed for the rotational constant yol. With the known molecular 37-factor and the electric dipole moment the adiabatic part of the Born-Oppenheimer correction can be extracted from the primary observa-tion on y01. The adiabatic correction is very similar in both molecules but differs from the results in the earlier measurements on PbS.

scholarly journals Mikrowellenspektrum, Struktur, Dipolmoment und internes Hinderungspotential von Dimethyldisulfid

1965 ◽  
Vol 20 (12) ◽  
pp. 1676-1681 ◽  
Author(s):  
D. Sutter ◽  
H. Dreizler ◽  
H. D. Rudolph
Keyword(s):  
Perturbation Theory ◽  
Dipole Moment ◽  
Angular Momentum ◽  
Internal Rotation ◽  
Stark Effect ◽  
Order Perturbation ◽  
Frequency Range ◽  
First Order ◽  
Cross Terms ◽  
Second Order Perturbation Theory

The microwave spectra of CD3 —S —S —CD3 and CH3 —S —S—CH3 have been measured in the frequency range from 5.5 to 34 kmc/sec. From the six rotational constants an r0-structure has been calculated. STARK-effect measurements have been made for the 101 —110 and 202—211 rotational transitions of CH3—S—S—CH3. The dipole moment was calculated to be (1.985±0.01) Debye. An approximate value for the barrier to internal rotation of the two methyl tops is given, V3= (1.6±0.1) kcal. The calculation has been based on triplet splittings of the rotational lines using second order perturbation theory in the torsional wavefunctions and neglecting first order and cross terms in angular momentum.

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.

ABSORPTION COEFFICIENTS OF SEVERAL ATMOSPHERIC GASES

1953 ◽  
Author(s):  
K. Watanabe ◽  
Murray Zelikoff ◽  
Edward C. Inn
Keyword(s):  
Atmospheric Gases ◽  
Absorption Coefficients

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.

Collision–induced absorption in gaseous methane at low temperatures

1986 ◽  
Vol 64 (7) ◽  
pp. 763-767 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Low Temperatures ◽  
Low Frequency ◽  
Frequency Region ◽  
Experimental Results ◽  
Published Data ◽  
Frequency Range ◽  
Simple Method ◽  
Induced Absorption ◽  
Good Agreement

A recently developed theory for collision-induced absorption in methane is compared with experimental results over a wider spectral range and at lower temperatures than previously reported. The present experimental results covering the frequency range below 400 cm−1 exhibit good agreement with other recently published data. The theory shows excellent agreement with experiment in the low-frequency region below approximately 200 cm−1 but underestimates the experimental data somewhat at higher frequencies. Possible theoretical reasons for this discrepancy are given. The theory represents a simple method of obtaining a good estimate of the collision-induced absorption spectra of methane in this frequency region and for extrapolating to lower temperatures for which experimentation is not feasible. In addition, the moments α1 and γ1are compared with earlier determinations and indicate good agreement with the previously obtained values for the octupole and hexadecapole moments of methane.

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