Collision Induced Absorption in N2, CO2, and H2 at 2.3 cm−1

1975 ◽  
Vol 53 (18) ◽  
pp. 1764-1776 ◽  
Author(s):  
I. R. Dagg ◽  
G. E. Reesor ◽  
J. L. Urbaniak
Keyword(s):  
Microwave Absorption ◽  
Loss Factor ◽  
Relaxation Times ◽  
Virial Coefficients ◽  
Low Frequency ◽  
Frequency Region ◽  
Induced Absorption ◽  
Three Body ◽  
Initial Measurement

Collision induced microwave absorption is reported in pure N2, CO2, and H2 in the region of 2.3 cm−1. For N2 the results are taken at temperatures ranging from 208 to 333 K and at densities ranging from 50 to 300 amagat. The parts of the loss factor which are proportional to the square and the cube of the density are found to depend respectively on T−1.55±0.12 and T−2.56±0.44. These results are well explained by the theory which relates the virial coefficients and relaxation times to the loss factor. Both the two and three body relaxation times, τ2 and τ3 follow very closely a T−0.5 dependence. The ratio of τ2/τ3 is found to be 0.83. For CO2 the results are taken at temperatures ranging from 273 to 363 K and at densities ranging from 8 to 80 amagat. The parts of the loss factor which are proportional to the square and cube of the density depend respectively on T−3.08±0.05 and T−5.4±0.059. These results together with existing infrared results show that τ2 is nearly proportional to T−0.5 and the ratio τ2/τ3 is 0.91 at 296 K. An initial measurement is reported for collision induced absorption in H2. The results for all three gases have been compared to previously reported results in the low frequency region.

Collision Induced Microwave Absorption in CO2 and CO2–Ar, CO2–CH4 Mixtures in the 2.3 cm−1 Region

1974 ◽  
Vol 52 (11) ◽  
pp. 973-978 ◽  
Author(s):  
I. R. Dagg ◽  
G. E. Reesor ◽  
J. L. Urbaniak
Keyword(s):  
Microwave Absorption ◽  
Virial Coefficient ◽  
Relaxation Times ◽  
Low Frequency ◽  
Low Density ◽  
Frequency Data ◽  
Density Region ◽  
Three Body ◽  
Correction Terms ◽  
Good Agreement

Collision induced microwave absorption is reported in pure CO2, and CO2–Ar, CO2–CH4 mixtures in the 70 GHz (2.3 cm−1) region at a temperature of 22 °C, using a sensitive cavity technique previously described. The results in pure CO2 in the very low density region from 5 to 30 amagat accurately establish the dependence of the loss on the square and cube of the density, and the relaxation times are calculated. The experimental results agree well with previously reported lower frequency data at 0.3–0.8 cm−1 which establishes the linear dependence on frequency of the absorption up to 2.3 cm−1. There is also good agreement with an extrapolation of higher frequency infrared results of Ho et al. The relaxation times associated with the two and three body collisions are shown to be nearly equal at room temperatures with τ2 = 0.84 × 10−12 s and τ3 = 1.0 × 10−12 s. Higher order dependence on the density is observed for the CO2–Ar and CO2–CH4 mixtures. The results are compared with earlier low frequency measurements at 0.8 cm−1 and with the theory of Maryott and Kryder, taking account of correction terms in the dielectric virial coefficient according to Bose and Cole.

Collision Induced Microwave Absorption in N2, CH4, and N2–Ar, N2–CH4 Mixtures at 1.1 and 2.3 cm−1

1974 ◽  
Vol 52 (9) ◽  
pp. 821-829 ◽  
Author(s):  
I. R. Dagg ◽  
G. E. Reesor ◽  
J. L. Urbaniak
Keyword(s):  
Microwave Absorption ◽  
Quadrupole Moment ◽  
Linear Dependence ◽  
Relaxation Times ◽  
High Sensitivity ◽  
Higher Order ◽  
Induced Absorption ◽  
High Q ◽  
Order Dependence

Collision induced microwave absorption is reported in pure N2, N2–Ar, N2–CH4, mixtures, and in pure CH4 in the 35 and 70 GHz regions (1.1 and 2.3 cm−1) at a temperature of 22 °C. The measurements are accomplished using overmoded high Q cavities capable of pressurization of up to 5000 p.s.i.g. The apparatus and method are described. With the high sensitivity attained, the results in pure N2 from 30 → 250 amagat reveal terms in the square and cube of the density from which the relaxation times are calculated. The linear dependence on frequency of the collision induced absorption up to 2.3 cm−1 is established. Higher order dependence on the density is observed in the N2–Ar and N2–CH4 mixtures. Various estimates of the quadrupole moment of N2 are given, making use of earlier results in other frequency regions.

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.

Submillimetric and millimetric collision-induced absorption spectra in compressed gaseous nitrogen using very low-frequency optical source

1991 ◽  
Vol 69 (10) ◽  
pp. 1264-1272 ◽  
Author(s):  
R. Occelli ◽  
H. Chaaban ◽  
J. M. Moynault ◽  
R. Coulon ◽  
A. Balsamo
Keyword(s):  
Nonlinear Crystal ◽  
Relaxation Times ◽  
Low Frequency ◽  
Theoretical Models ◽  
Gaseous Nitrogen ◽  
Optical Source ◽  
Shape Model ◽  
Induced Absorption ◽  
Close Frequency ◽  
Absorption Measurements

A (sub)millimetric source is obtained by difference-frequency mixing in a nonlinear crystal. It allows investigation of spectral absorption between 4 and 40 cm−1 with a new two-beam spectroscopic mounting. The complete mounting is described. The measurement method is given in detail. Compressed gaseous nitrogen-induced absorption measurements are used to calculate relaxation times and spectral moments. Comparisons are made with other measurements in close frequency regions, and theoretical models and an empirical line-shape model.

Magnetic sputtering of FeNi/C bilayer film on SiC fibers for effective microwave absorption in the low-frequency region

2020 ◽  
Author(s):  
Tong Guo ◽  
Ben Huang ◽  
Changgeng Li ◽  
Yumin Lou ◽  
Xiu-Zhi Tang ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Low Frequency ◽  
Frequency Region ◽  
Bilayer Film ◽  
Sic Fibers ◽  
Magnetic Sputtering

DIELECTRIC PROPERTIES OF PLASMA POLYMERIZED N,N,3,5 TETRAMETHYLANILINE THIN FILMS

2011 ◽  
Vol 18 (01n02) ◽  
pp. 53-60 ◽  
Author(s):  
H. AKTHER ◽  
A. H. BHUIYAN
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Relaxation Times ◽  
Electrical Conductance ◽  
Low Frequency ◽  
Ring Structure ◽  
Frequency Region ◽  
Localized States ◽  
High Frequency Region ◽  
Capacitively Coupled

Plasma polymerized thin films of aluminium/thin film/aluminium configuration were deposited at room temperature by a parallel plate capacitively coupled glow discharge reactor using N,N,3,5 tetramethylaniline (TMA) as a precursor. The infrared spectroscopic analyses revealed that plasma polymerized TMA (PPTMA) films contained an aromatic ring structure with NC and CH side groups, presence of C = O was also evident. The differential thermal analysis and thermogravimetric analysis of PPTMA thin film was thermally stable up to about 505 K. The scanning electron microscopy of PPTMA thin film showed a smooth, flawless and pinhole free surface. The capacitance and ac electrical conductance of PPTMA thin films were measured as functions of frequency (100 < f < 105 Hz) and temperature (300 < T < 450 K). The electrical conductivity is more dependent on temperature in the low frequency region than that in the high frequency region. In PPTMA thin films the conduction may be dominated by hopping of carriers between the localized states at low temperatures and thermally excited at the high temperatures. The activation energies are estimated to be about 0.05 eV in the low temperature and 0.23 eV in the high temperature. Dielectric constant decreases with the increase of frequency and that decreases with the increase of temperature but dielectric loss increases with increasing frequency with a minimum in the low frequency region. The temperature-dependence of the Cole-Cole diagram shows the existence of distribution of dielectric relaxation times in the PPTMA thin films.

Determination of Two‐ and Three‐Body Relaxation Times from Collision‐Induced Absorption

1967 ◽  
Vol 46 (5) ◽  
pp. 1557-1561 ◽  
Author(s):  
George Birnbaum ◽  
Howard B. Levine ◽  
Donald A. McQuarrie
Keyword(s):  
Relaxation Times ◽  
Induced Absorption ◽  
Three Body

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

scholarly journals Enhanced Magnetic Microwave Absorption at Low‐Frequency Band by Ferrite Assembled Microspheres with Controlled Components and Morphologies

2021 ◽  
Author(s):  
Mengqiu Huang ◽  
Xuefeng Yu ◽  
Lei Wang ◽  
Jiwei Liu ◽  
Wenbin You ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Frequency Band ◽  
Low Frequency
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