Temperature dependent collision-induced absorption in nitrogen

The collision-induced rotational translational spectrum of gaseous N2 has been measured in the temperature range 228–343 K at six different temperatures. The measurements were made with a Fourier transform spectrometer in the 25 to 360 cm−1 region and at 15.1 and 84.2 cm−1 with far infrared (FIR) laser. Previously obtained microwave data at 2.3 and 4.7 cm−1 have been used in defining the complete spectrum. Using a recently developed theory for quadrupolar-induced absorption, we find that the calculated quadrupole moment is independent of temperature and has a magnitude in close agreement with the recommended values of several other workers; i.e., Q = 1.46 B. The calculated value depends on the particular form of the intermolecular potential and this dependence is examined in some detail. A contribution to the absorption originating primarily from hexadecapolar and overlap induction has been observed in agreement with theoretical estimates and leads to an estimated value for the hexadecapolar moment [Formula: see text].

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

Canadian Journal of Physics ◽

10.1139/p82-003 ◽

1982 ◽

Vol 60 (1) ◽

pp. 16-25 ◽

Cited By ~ 4

Author(s):

I. R. Dagg ◽

W. Smith ◽

L. A. A. Read

Keyword(s):

Absorption Spectrum ◽

Far Infrared ◽

Fourier Transform Spectrometer ◽

Density Range ◽

Fir Laser ◽

Quadrupolar Interaction ◽

Induced Absorption ◽

Upper Limit ◽

Experimental Values ◽

Microwave Techniques

The collision-induced absorption spectrum of gaseous ethane has been measured at 295 K over a density range from 12 to 45 amagat in the 50–360 cm−1 region and at densities up to 59 amagat at 4.6, 17.4, and 29.6 cm−1. The measurements were made using a Fourier transform spectrometer, an HCN laser, a FIR laser, and microwave techniques. A collision-induced torsional absorption is observed which is centred at 280 cm−1 and is superimposed on the collision-induced rotation–translation absorption. Theoretically, the latter absorption can be ascribed to quadrupolar interaction. This theory has been used to extract estimates for the quadrupole moment of ethane. The results provide an upper limit for the value of Q = −1.28 × 10−26 esu. Lower estimates are also given which reflect a larger contribution to the absorption from the torsional band by using the known absorption profiles for N2 and C2H4. These estimates are compared with other theoretical and experimental values.

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Spectral lineshapes of collision-induced absorption (CIA) using isotropic intermolecular potential for N2-CH4

Journal of Computational Methods in Sciences and Engineering ◽

10.3233/jcm-210049 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1063-1078

Author(s):

M.S.A. El-Kader ◽

G. Maroulis ◽

T. Bancewicz

Keyword(s):

Potential Model ◽

Dipole Moments ◽

Molecular Nitrogen ◽

Intermolecular Potential ◽

Gaseous Mixtures ◽

Induced Absorption ◽

Induced Dipole ◽

Different Temperatures ◽

Experimental Absorption ◽

Good Agreement

Quantum mechanical lineshapes of collision-induced absorption (CIA) at different temperatures are computed for gaseous mixtures of molecular nitrogen and methane using theoretical values for the induced dipole moments and intermolecular potential as input. Comparison with theoretical absorption spectra shows satisfactory agreement. An empirical model of the dipole moment which reproduces the experimental spectra and the first three spectral moments more closely than the fundamental theory, is also presented. Good agreement between computed and experimental absorption lineshapes is obtained when a potential model which is constructed from the thermophysical and transport properties is used.

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

Canadian Journal of Physics ◽

10.1139/p81-008 ◽

1981 ◽

Vol 59 (1) ◽

pp. 57-65 ◽

Cited By ~ 8

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.

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