THE PRESSURE-INDUCED ROTATIONAL ABSORPTION SPECTRUM OF HYDROGEN: I. A STUDY OF THE ABSORPTION INTENSITIES

1959 ◽  
Vol 37 (3) ◽  
pp. 362-376 ◽  
Author(s):  
Z. J. Kiss ◽  
H. P. Gush ◽  
H. L. Welsh
Keyword(s):  
Absorption Spectrum ◽  
Kinetic Energy ◽  
Infrared Spectrum ◽  
Absorption Coefficient ◽  
Quadrupole Interaction ◽  
Vibrational Band ◽  
Absorption Process ◽  
Relative Kinetic ◽  
Good Agreement ◽  
Gas Pressures

The pressure-induced infrared spectrum of H2 and mixtures of H2 with N2, He, Ne, A, Kr, and Xe was measured in the region 300–1400 cm−1 at total gas pressures up to 250 atm at 300° K and, where possible, at 195° K and 85° K. The spectrum shows greatly broadened S lines (ΔJ = + 2) with half widths which decrease as the temperature is lowered. The integrated absorption coefficient of the band is of the form [Formula: see text], where ρƒ is the density of the perturbing gas, except in the case of Xe for which a cubic term, [Formula: see text], is also necessary. The binary coefficient α1 increases by a factor of 28 in going from He to Xe. The theoretical band intensity, calculated on the basis of quadrupole interaction alone, is in good agreement with the experimental value only for Xe as perturbing gas; in other cases the calculated value is appreciably less than the observed value. The shape of the absorption contours suggests that the S lines are overlaid by a continuum increasing in intensity towards lower frequencies. This continuum is interpreted as the counterpart of the QR component in the vibrational band, that is, a collision-induced absorption due to overlap interaction in which the relative kinetic energy of the collision partners changes in the absorption process.

INDUCED INFRARED ABSORPTION IN HYDROGEN AND HYDROGEN - FOREIGN GAS MIXTURES AT PRESSURES UP TO 1500 ATMOSPHERES

1954 ◽  
Vol 32 (4) ◽  
pp. 291-312 ◽  
Author(s):  
D. A. Chisholm ◽  
H. L. Welsh
Keyword(s):  
Kinetic Energy ◽  
Absorption Band ◽  
Absorption Coefficient ◽  
Infrared Absorption ◽  
High Frequency ◽  
Absorption Process ◽  
Rate Of Increase ◽  
Frequency Components ◽  
Relative Kinetic ◽  
Gas Pressures

The pressure-induced fundamental infrared absorption band of hydrogen has been investigated in the pure gas and in hydrogen–helium, hydrogen–nitrogen, and hydrogen–argon mixtures for gas pressures up to 1500 atm. and temperatures in the range 80°–376°K. At the higher densities the rate of increase of the integrated absorption coefficient with density is anomalously large; this effect is interpreted in terms of finite molecular volumes. The Q branch has been shown to consist of three components QP, Qq, and QR. The separation of the maxima in the low- and high-frequency components, QP and QR, depends on the perturbing gas and increases linearly with its density; the separation and relative intensities of the components are also strongly dependent on the temperature. It is proposed that this splitting of the Q branch is caused by the participation of the relative kinetic energy of the colliding molecules in the absorption process for collisions in the region of overlap forces. The Qq component and the S lines show no splitting and are probably produced by collisions in the region of quadrupole interaction.

Urbach's rule in impurity absorption

1969 ◽  
Vol 47 (16) ◽  
pp. 1703-1708 ◽  
Author(s):  
Dennis Dunn
Keyword(s):  
Absorption Spectrum ◽  
Absorption Coefficient ◽  
Photon Energy ◽  
Valence Electron ◽  
Impurity State ◽  
Function Technique ◽  
Absorption Process ◽  
Impurity Absorption ◽  
Long Wavelength ◽  
State Electron

We have investigated theoretically the shape of the long-wavelength edge of the impurity absorption spectrum in an insulator (or semiconductor) by means of a Green's function technique. The absorption process is assumed to be the excitation of a valence electron into a previously unoccupied impurity state. We have shown that Urbach's rule is obeyed, that is the absorption coefficient depends exponentially upon the photon energy, if either the valence electron or the impurity state electron is coupled strongly to monoenergetic phonons.

PRESSURE-INDUCED INFRARED ABSORPTION OF HYDROGEN AND HYDROGEN – FOREIGN GAS MIXTURES IN THE RANGE 1500–5000 ATMOSPHERES

1958 ◽  
Vol 36 (1) ◽  
pp. 88-103 ◽  
Author(s):  
W. F. J. Hare ◽  
H. L. Welsh
Keyword(s):  
Absorption Coefficient ◽  
Infrared Absorption ◽  
Room Temperature ◽  
Pure Hydrogen ◽  
Vibrational Transition ◽  
Absorption Process ◽  
Quadrupole Interactions ◽  
Relative Kinetic ◽  
Very High ◽  
Absorption Of Hydrogen

The pressure-induced infrared absorption of hydrogen was studied in pure hydrogen and in hydrogen–helium, hydrogen–argon, and hydrogen–nitrogen mixtures at pressures up to 5000 atm. at room temperature. The integrated absorption coefficient can be expressed in the form α1ρaρp + α2ρaρp2 over the whole range of densities (ρa = density of H2, ρp = density of the perturbing gas, [Formula: see text] in the mixture experiments). The coefficient α2 is much smaller than predicted from the effect of finite molecular volumes; this is interpreted as a partial cancellation of the induced moments in ternary collisions. The splitting of the Q branch of the fundamental, which is due to the participation of the relative kinetic energies of the colliding molecules in the absorption process, increases linearly with the density because of ternary collisions; a more rapid increase observed at very high densities is not yet explained. The components of the overtone and double vibrational transition, like the QQ and S components of the fundamental, show no splitting or broadening with increasing density; these absorptions are believed to be due to quadrupole interactions while the QP and QR components of the fundamental are due to overlap interactions.

Effective Dielectric Function of Porous Silicon: the Transverse Component

1994 ◽  
Vol 358 ◽  
Author(s):  
G. Gumbs
Keyword(s):  
Absorption Spectrum ◽  
Absorption Coefficient ◽  
Electron Density ◽  
Quantum Wires ◽  
Interband Transition ◽  
Incident Light ◽  
Transverse Component ◽  
Effect Of Temperature ◽  
High Electron ◽  
Confining Potential

ABSTRACTA self-consistent many-body theory is developed to study the effect of temperature and electron density on the interband absorption coefficient and the frequency-dependent refractive index for an array of isolated quantum wires. The peaks in the absorption coefficient correspond to interband transitions resulting in the resonant absorption of light. The oscillations in the derivative spectrum are due to the quantization of the energy levels related to the in-plane confining potential for such reduced dimensional systems. There are appreciable changes in the absorption spectrum when the electron density or temperature is increased. One interband transition peak is suppressed in the high electron density limit and the thermal depopulation effect on the electron subbands can be easily seen when the temperature is high. We also find that the exciton coupling weakens the shoulder features in the absorption spectrum. This study is relevant to optical characterization of the confining potential and the areal density of electrons using photoreflectance. By using incident light with tunable frequencies in the interband excitation regime, contactless photoreflectance measurements may be carried out and the data compared with our calculations. By fitting the numerical results to the peak positions of the photoreflectance spectrum, the number of electrons in each wire may be extracted.

Disorientation of Cs(62P1/2) atoms, induced in collisions with noble gases

1976 ◽  
Vol 54 (7) ◽  
pp. 748-752 ◽  
Author(s):  
B. Niewitecka ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Noble Gas ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Buffer Gas ◽  
Resonance Fluorescence ◽  
Circularly Polarized ◽  
Low Field ◽  
Good Agreement ◽  
Gas Pressures

The disorientation of 62P1/2 cesium atoms, induced in collisions with noble gas atoms in their ground states, was systematically investigated by monitoring the depolarization of cesium resonance fluorescence in relation to noble gas pressures. The Cs atoms, contained together with a buffer gas in a fluorescence cell and located in zero magnetic field, were excited and oriented by irradiation with circularly polarized 8943 Å resonance radiation, and the resonance fluorescence, emitted in an approximately backward direction, was analyzed with respect to circular polarization. The experiments yielded the following disorientation cross sections which have been corrected for the effects of nuclear spin: Cs–He: 4.9 ± 0.7 Å2; Cs–Ne: 2.1 ± 0.3 Å2; Cs–Ar: 5.6 ± 0.8 Å2; Cs–Kr: 5.8 ± 0.9 Å2; Cs–Xe: 6.3 ± 0.9 Å2. The results are in good agreement with most of the available zero-field and low-field data.

Heat Transfer Committee and Turbomachinery Committee Best Paper of 1996 Award: The Path to Predicting Bypass Transition

1997 ◽  
Vol 119 (3) ◽  
pp. 405-411 ◽  
Author(s):  
R. E. Mayle ◽  
A. Schulz
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Energy Equation ◽  
Free Stream ◽  
Bypass Transition ◽  
Turbulence Level ◽  
Free Stream Turbulence ◽  
Energy Profiles ◽  
Computer Codes ◽  
Good Agreement

A theory is presented for calculating the fluctuations in a laminar boundary layer when the free stream is turbulent. The kinetic energy equation for these fluctuations is derived and a new mechanism is revealed for their production. A methodology is presented for solving the equation using standard boundary layer computer codes. Solutions of the equation show that the fluctuations grow at first almost linearly with distance and then more slowly as viscous dissipation becomes important. Comparisons of calculated growth rates and kinetic energy profiles with data show good agreement. In addition, a hypothesis is advanced for the effective forcing frequency and free-stream turbulence level that produce these fluctuations. Finally, a method to calculate the onset of transition is examined and the results compared to data.

scholarly journals The spectrum of thallium fluoride

1937 ◽  
Vol 160 (901) ◽  
pp. 242-253 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Kinetic Energy ◽  
The Other ◽  
Molecular Spectra ◽  
Absorption Tube ◽  
Saturated Vapour ◽  
Long Wave ◽  
Original Investigation ◽  
Wave Edge

This study of the thallium fluoride spectrum was undertaken as part of a detailed investigation into the molecular spectra of the series of heavy diatomic fluorides HgF, TlF, PbF and BiF. Whereas the spectra of PbF (Rochester 1936) and BiF (Howell 1936), of which analyses have already been published, contain no very unusual features the TlF spectrum is particularly rich in them, so that it has seemed desirable to extend the original investigation in order to include the other halides of thallium. The absorption spectrum of the fluoride has already been examined by Boizova and Butkow (1936), their findings being summarized below: 1— A continuum at 2200 A appears when the absorption tube is at a temperature of 155° C. Its long-wave edge moves towards the red with increase of temperature, being at 2700 for the unsaturated vapour and at 3400 for the saturated vapour when the temperature is 280° C. They attributed this continuum to the dissociation of Tl 2 F 2 . Tl 2 F 2 → 2TlF + kinetic energy.

Reactive mode composition factor analysis of transition states: the case of coupled electron–proton transfers

2019 ◽  
Vol 21 (45) ◽  
pp. 24912-24918 ◽  
Author(s):  
Mauricio Maldonado-Domínguez ◽  
Daniel Bím ◽  
Radek Fučík ◽  
Roman Čurík ◽  
Martin Srnec
Keyword(s):  
Factor Analysis ◽  
Kinetic Energy ◽  
Isotope Effects ◽  
Transition States ◽  
Kinetic Isotope Effects ◽  
Composition Factor ◽  
Kinetic Isotope ◽  
Proton Transfers ◽  
Relative Kinetic ◽  
Reactive Mode

The kinetic energy distribution in the reactive mode in transition states correlates the asynchronicity of CPET with relative kinetic isotope effects.

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