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

1982 ◽  
Vol 60 (1) ◽  
pp. 16-25 ◽  
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.

Temperature dependent collision-induced absorption in nitrogen

1984 ◽  
Vol 62 (4) ◽  
pp. 338-347 ◽  
Author(s):  
N. W. B. Stone ◽  
L. A. A. Read ◽  
A. Anderson ◽  
I. R. Dagg ◽  
W. Smith
Keyword(s):  
Close Agreement ◽  
Far Infrared ◽  
Intermolecular Potential ◽  
Fourier Transform Spectrometer ◽  
Fir Laser ◽  
Complete Spectrum ◽  
Temperature Dependent ◽  
Induced Absorption ◽  
Different Temperatures ◽  
Microwave Data

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].

Rototranslational absorption in gaseous H2–Ar mixtures at intermediate densities

1989 ◽  
Vol 67 (6) ◽  
pp. 599-604 ◽  
Author(s):  
P. Dore ◽  
A. Filabozzi ◽  
G. Birnbaum
Keyword(s):  
Absorption Spectrum ◽  
Low Density ◽  
Density Range ◽  
Line Profiles ◽  
Induced Absorption ◽  
Density Limit ◽  
Density Effects ◽  
Low Density Limit ◽  
Experimental Values ◽  
Three Body

We present the measurements and analysis of the density effects on the rototranslational absorption spectrum of H2–Ar mixtures, for densities up to about 200 amagat. This density range is intermediate between the low-density limit, in which the spectrum is due to binary interactions, and the high-density range, in which density produces the so-called density-narrowing effect, which was studied previously. We find in the density range currently explored that density (ρ) effects are clearly evident and are well accounted for by considering a negative ρ3 contribution to the absorption besides the dominant ρ2 contribution. Experimental values of the two-body and three-body zeroth moments are obtained. We also obtain experimental line profiles for these two contributions. Even if the accuracy of the ρ3 profile is low, this work presents the first ρ3 line determined from measurements of collision-induced absorption.

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.

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.

Collision-induced absorption in gaseous mixtures of nitrogen and methane

1986 ◽  
Vol 64 (11) ◽  
pp. 1467-1474 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Far Infrared ◽  
Frequency Region ◽  
Theoretical Development ◽  
Gaseous Mixtures ◽  
Induced Absorption ◽  
Rotational Spectra ◽  
Theoretical Line ◽  
Microwave Techniques ◽  
Lower Frequency Region ◽  
Good Agreement

The collision-induced absorption spectra of nitrogen–methane gas mixtures have been measured in the spectral region below 400 cm−1 at four temperatures, namely, 212, 179, 149, and 126 K. The measurements have involved the use of Fourier-transform infrared and microwave techniques as well as a far-infrared laser operating at 84.2 and at 15.1 cm−1. These are compared with a theoretical line shape obtained from a convolution of free rotational spectra and a translational component as determined from information theory. The calculated spectra show good agreement with the experimental results only in the lower frequency region. An important feature of the theoretical development is that no adjustable parameters need be introduced.

Collision-induced absorption in a gaseous mixture of nitrogen and argon

1986 ◽  
Vol 64 (1) ◽  
pp. 7-15 ◽  
Author(s):  
I. R. Dagg ◽  
A. Anderson ◽  
S. Yan ◽  
W. Smith ◽  
C. G. Joslin ◽  
...  
Keyword(s):  
Laser System ◽  
Gaseous Mixture ◽  
Far Infrared ◽  
Theoretical Development ◽  
Induced Absorption ◽  
Theoretical Line ◽  
Microwave Techniques ◽  
Rotation Spectrum ◽  
System Operating ◽  
Good Agreement

The collision-induced absorption spectrum of a nitrogen–argon gas mixture is treated theoretically and the theory is applied to results obtained by us in the spectral region below 360 cm−1 at four temperatures, namely, 126, 149, 179, and 212 K. The measurements have involved the use of Fourier transform infrared and microwave techniques as well as a far-infrared laser system operating at 84.2 and 15.1 cm−1. The theoretical line shape is obtained from a convolution of a free rotation spectrum and a translational component. The spectra calculated from either information theory alone or combined with Mori theory both show good agreement with experimental results, especially above 30 cm−1. An important feature of the theoretical development is that no adjustable parameters need to be introduced.

scholarly journals Far-infrared absorption in cubic ZnS

1976 ◽  
Vol 54 (10) ◽  
pp. 1053-1060 ◽  
Author(s):  
E. A. Kwasniewski ◽  
E. S. Koteles ◽  
W. R. Datars
Keyword(s):  
Absorption Spectrum ◽  
Infrared Absorption ◽  
Phonon Dispersion ◽  
Far Infrared ◽  
Fourier Transform Spectrometer ◽  
High Symmetry ◽  
Phonon Density ◽  
Zone Boundary ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves

Far-infrared absorption in cubic ZnS due to single-phonon and two-phonon processes was measured with a high resolution, far-infrared Fourier transform spectrometer. A 14-parameter lattice dynamical shell model was fitted to phonon dispersion curves measured by Vagelatos et al. The two-phonon density-of-states calculated with these parameters was compared with the absorption spectrum. Two-phonon combinations and their locations in the Brillouin zone were identified with features of the absorption spectrum. Critical points were found on or near the zone boundary and not only at high symmetry points as suggested previously.

Far-infrared absorption in CdTe

1977 ◽  
Vol 55 (22) ◽  
pp. 2013-2018 ◽  
Author(s):  
E. Batalla ◽  
E. S. Koteles ◽  
W. R. Datars
Keyword(s):  
Absorption Spectrum ◽  
Brillouin Zone ◽  
Infrared Absorption ◽  
Far Infrared ◽  
High Accuracy ◽  
Compound Semiconductor ◽  
Model Parameters ◽  
Fourier Transform Spectrometer ◽  
Phonon Density ◽  
Phonon Density Of States

Far-infrared absorption in the II–VI compound semiconductor Cd Te has been measured using a Fourier transform spectrometer. Two-phonon density-of-states curves were calculated from shell model parameters determined by Rowe, Nicklow, Price, and Zanio and were compared to the high-accuracy absorption spectrum. Two-phonon combinations and the location of the corresponding critical points in the Brillouin zone were identified with features in the absorption spectrum. From these assignments, accurate values of some normal mode frequencies at certain points in the Brillouin zone were determined.

On the Theory of Collision-Induced Absorption in Rare Gas Mixtures

1971 ◽  
Vol 49 (7) ◽  
pp. 837-847 ◽  
Author(s):  
S. L. Brenner ◽  
D. A. McQuarrie
Keyword(s):  
Absorption Spectrum ◽  
Dipole Moment ◽  
Far Infrared ◽  
Gas Mixtures ◽  
Moment Function ◽  
Rare Gas ◽  
Induced Absorption ◽  
Induced Dipole ◽  
Calculated Equilibrium

The observed far-infrared collision-induced absorption of helium–argon mixtures is used to determine the parameters in an induced-dipole moment function of the form[Formula: see text]It is shown that, with this form of μ(r), the values of the constants μo, ρ, and c7 that are necessary to fit the first two moments of the observed absorption contour are in disagreement with the available theoretical values of these constants. Possible explanations for this disagreement are discussed in the paper. Finally, it is shown that if μ(r) were known, it is possible to obtain an excellent representation of the entire absorption spectrum from a knowledge of only the first three moments, which are easily calculated equilibrium quantities.

Sign in / Sign up

Export Citation Format

Share Document