VIBRATIONAL FREQUENCY PERTURBATIONS IN THE RAMAN SPECTRUM OF COMPRESSED GASEOUS HYDROGEN

1964 ◽  
Vol 42 (6) ◽  
pp. 1058-1069 ◽  
Author(s):  
A. D. May ◽  
G. Varghese ◽  
J. C. Stryland ◽  
H. L. Welsh
Keyword(s):  
Raman Band ◽  
Intermolecular Forces ◽  
Hydrogen Gas ◽  
High Spectral Resolution ◽  
Intermolecular Potential ◽  
Dispersion Forces ◽  
Frequency Shifts ◽  
Linear Coefficient ◽  
Relative Population ◽  
Good Agreement

The frequencies of the Q(J) lines of the fundamental Raman band of compressed hydrogen gas were measured with high spectral resolution for a series of densities from 25 to 400 Amagat units at 300 °K and 85 °K. The frequency shifts are expressed as a power series in the gas density. The linear coefficient at a given temperature has the form aJ = ai + ae(nJ/n), where ai, constant for all the Q lines, can be interpreted in terms of isotropic intermolecular forces, and ae(nJ/n), proportional to the relative population of the initial J level, arises from the inphase coupled oscillation of pairs of molecules. The temperature variation of ai is analyzed on the basis of the Lennard-Jones intermolecular potential and the molecular pair distribution function. The repulsive overlap forces and the attractive dispersion forces give, respectively, positive and negative contributions to ai, which can be characterized by the empirical parameters Krep and Katt. The values of Katt and ae are in good agreement with calculations based on the polarizability model of the dispersion forces. The relation of the results to the Raman frequency shifts in solid hydrogen is discussed.

Pressure shifts in the vibrational Raman spectra of hydrogen and deuterium, 315–85 K

1978 ◽  
Vol 56 (8) ◽  
pp. 1102-1108 ◽  
Author(s):  
E. C. Looi ◽  
J. C. Stryland ◽  
H. L. Welsh
Keyword(s):  
Standard Deviation ◽  
Raman Spectra ◽  
Rotational Level ◽  
The Other ◽  
Dispersion Forces ◽  
Temperature Dependent ◽  
Vibrational Coupling ◽  
Frequency Shifts ◽  
Linear Coefficient ◽  
Gas Density

The Raman frequencies of the Q(J) lines of the fundamental Raman bands of compressed H2 and D, were measured with a standard deviation of ±0.02 cm−1 at gas densities from 10 to 100 amagat at several temperatures in the range 315 to 85 K. The frequency shifts are negative and linear in the gas density; they range up to −1.2 cm−1 for H2 and −0.7 cm−1 for D2. The linear coefficient for the Q(J) line has the form, ai + ac(nJ/n), where nJ/n is the fractional population of the rotational level, J, and ai and ac are constants independent of J. The constant ai is strongly temperature-dependent and is interpreted as the vibrational shift due to isotropic dispersion and overlap forces. On the other hand, ac is practically temperature-independent and is believed to arise from vibrational coupling through dispersion forces.

Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

1977 ◽  
Vol 32 (1) ◽  
pp. 57-60 ◽  
Author(s):  
H. E. Gunilla Knape ◽  
Lena M. Torell
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Viscosity Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Hypersonic Velocity ◽  
Frequency Shifts ◽  
Bulk Viscosity Coefficient ◽  
Good Agreement

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper­ sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap­ proaching the classical attenuation. The results are in good agreement with Mountain's theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

The transient start of supersonic jets

2007 ◽  
Vol 578 ◽  
pp. 331-369 ◽  
Author(s):  
MATEI I. RADULESCU ◽  
CHUNG K. LAW
Keyword(s):  
Numerical Simulations ◽  
Ambient Air ◽  
Hydrogen Gas ◽  
Shock Interactions ◽  
Round Jets ◽  
Reactive Gases ◽  
Acoustic Instabilities ◽  
Diffusive Fluxes ◽  
Experimental Findings ◽  
Good Agreement

This study investigates the initial transient hydrodynamic evolution of highly under-expanded slit and round jets. A closed-form analytic similarity solution is derived for the temporal evolution of temperature, pressure and density at the jet head for vanishing diffusive fluxes, generalizing a previous model of Chekmarev using Chernyi's boundary-layer method for hypersonic flows. Two-dimensional numerical simulations were also performed to investigate the flow field during the initial stages over distances of ~ 1000 orifice radii. The parameters used in the simulations correspond to the release of pressurized hydrogen gas into ambient air, with pressure ratios varying between approximately 100 and 1000. The simulations confirm the similarity laws derived theoretically and indicate that the head of the jet is laminar at early stages, while complex acoustic instabilities are established at the sides of the jet, involving shock interactions within the vortex rings, in good agreement with previous experimental findings. Very good agreement is found between the present model, the numerical simulations and previous experimental results obtained for both slit and round jets during the transient establishment of the jet. Criteria for Rayleigh–Taylor instability of the decelerating density gradients at the jet head are also derived, as well as the formulation of a model addressing the ignition of unsteady expanding diffusive layers formed during the sudden release of reactive gases.

Isotopic Thermal Diffusion Factors for Helium and Neon at Low Temperatures

1963 ◽  
Vol 18 (2) ◽  
pp. 242-245 ◽  
Author(s):  
W. W. Watson ◽  
A. J. Howard ◽  
N. E. Miller ◽  
R. M. Shiffrin
Keyword(s):  
Thermal Diffusion ◽  
Low Temperatures ◽  
Quantum Corrections ◽  
Intermolecular Potential ◽  
De Vries ◽  
Lower Temperature ◽  
Improved Accuracy ◽  
Good Agreement

With an all-metal “swing separator” having unique features, thermal diffusion factors αT for He3/He4 and Ne20Ne22 have been measured with improved accuracy down to average gas temperatures T̅=136°K. For helium αT is 0.0696 ± 0.0010 at 136°K, dropping gradually to 0.0651 ±0.0010 at 313°K. These data, plus measurements by Van der Valk and de Vries at somewhat higher temperatures, agree best with values predicted by an exp-six intermolecular potential with ε/k=9.16 and α=12.7. We are extending these helium measurements down to T=4°K for the lower temperature, to detect if possible quantum corrections to the intermolecular potential. For neon αT increases from 0.0166 ± 0.0010 at 136°K to 0.0233 ± 0.0020 at 310°K, considerably higher than our previously reported values. These T. D. factors for neon are in good agreement with values calculated from an exp-six potential with ε/k = 46.0 ± 0.6 and α=13.

London – van der Waals forces and torques exerted on an ellipsoidal particle by a nearby semi-infinite slab

1981 ◽  
Vol 59 (13) ◽  
pp. 2004-2018 ◽  
Author(s):  
Howard Brenner ◽  
Lawrence J. Gajdos
Keyword(s):  
Potential Energy Function ◽  
Intermolecular Forces ◽  
Separation Distance ◽  
Intermolecular Potential ◽  
Integration Scheme ◽  
Intermolecular Potentials ◽  
Ellipsoidal Particle ◽  
Principal Axes ◽  
Infinite Slab ◽  
Centrally Symmetric

A Hamaker-type integration of the pairwise en vacuo intermolecular forces is performed for a homogeneous triaxial ellipsoidal particle in proximity to a homogeneous semi-infinite slab bounded by a plane wall. The orientation of the ellipsoid relative to the plane is taken to be arbitrary, as too is its distance from the plane. The integrated potential energy function of the ellipsoid with respect to the slab is found to possess nonadditive positional and orientational contributions. This macroscopic potential is employed to compute the force and torque on the ellipsoid as functions of both its position and orientation relative to the plane.The novel integration scheme pertains to centrally-symmetric pairwise intermolecular potentials of arbitrary functional form. Specific results are derived for classical inverse-power intermolecular potentials possessing both attractive (r−n) and repulsive (−r−m) additive components (with n > m). In stable equilibrium the ellipsoid aligns itself with the shortest of its three principal axes perpendicular to the bounding wall, and at a separation distance comparable to the length scale of the intermolecular potential itself.

scholarly journals Temperature-Dependent Raman Spectroscopic Study of the Double Molybdate KBi(MoO4)2

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5453
Author(s):  
Min Wang ◽  
Changhao Wang ◽  
Jian Wang ◽  
Liming Lu ◽  
Xiaoye Gong ◽  
...  
Keyword(s):  
High Temperature ◽  
Raman Spectra ◽  
Monoclinic Phase ◽  
Raman Band ◽  
Vibrational Modes ◽  
Temperature Dependent ◽  
Raman Spectroscopic ◽  
Thermal Stability Of ◽  
Good Agreement

In situ high-temperature Raman spectra of polycrystalline KBi(MoO4)2 were recorded from room temperature to 1073 K. Thermal stability of the monoclinic KBi(MoO4)2 was examined by temperature-dependent XRD. The monoclinic phase transformed into the scheelite tetragonal structure at 833 K, and then to the monoclinic phase at 773 K. Quantum chemistry ab initio calculation was performed to simulate the Raman spectra of the structure of KBi(MoO4)2 high-temperature melt. The experimental Raman band at 1023 K was deconvoluted into seven Gaussian peaks, and the calculated results were in good agreement with the experimental data. Therefore, the vibrational modes of Raman peaks of molten KBi(MoO4)2 were assigned. It was confirmed that the isolated structure of [Bi(MoO4)2]− monomer, consisting of Mo6+ centers and Bi3+ sub-centers connected by edge-sharing, mainly exists in the melt of KBi(MoO4)2.

Rotational temperature profiles of shock waves in diatomic gases

1971 ◽  
Vol 49 (2) ◽  
pp. 337-351 ◽  
Author(s):  
A. K. Macpherson
Keyword(s):  
Shock Waves ◽  
Rotational Temperature ◽  
Rotational Velocity ◽  
Three Dimensional ◽  
Intermolecular Potential ◽  
Collision Dynamics ◽  
Density Profiles ◽  
Frequency Distributions ◽  
Dimensional Approximation ◽  
Good Agreement

The variation of the translational temperature, rotational temperature, and density through shock waves in oxygen and nitrogen was studied using classical laws of mechanics and a Monte Carlo scheme. The collision dynamics were calculated using an intermolecular potential by Parker with both a two-dimensional approximation and the full three-dimensional calculations. The rotational velocity frequency distributions were also calculated. The average number of collisions a molecule will experience a t various stages passing through a shock wave were found and plotted with the temperature and density profiles. The nitrogen results were compared with experimental results and good agreement was found. This also provided a method for giving a first approximation to the three-dimensional intermolecular potential.

Theoretical Analysis of Porosity in an Ordered Porous Copper Fabricated by Continuous Unidirectional Solidification

2018 ◽  
Vol 933 ◽  
pp. 136-141
Author(s):  
Rong Cao ◽  
Qing Lin Jin
Keyword(s):  
High Pressure ◽  
Theoretical Model ◽  
Theoretical Analysis ◽  
Processing Parameters ◽  
Unidirectional Solidification ◽  
Hydrogen Gas ◽  
Porous Copper ◽  
Gas Atmosphere ◽  
Ordered Porous ◽  
Good Agreement

Ordered porous copper with elongated pores has been fabricated by a continuous unidirectional solidification method in a hydrogen gas atmosphere with high pressure. The porosity of the ordered porous copper is significantly affected by the pressure of hydrogen. A theoretical model is developed to get the relation between the porosity and the processing parameters. The calculated values are in good agreement with the experimental results. Key words: Unidirectional solidification; Ordered porous copper; Porosity; Modeling.

Fourier Deconvolution of the Amide I Raman Band of Proteins as Related to Conformation

1988 ◽  
Vol 42 (5) ◽  
pp. 819-826 ◽  
Author(s):  
Heino Susi ◽  
D. Michael Byler
Keyword(s):  
Raman Band ◽  
Broad Band ◽  
Gaussian Function ◽  
Specific Protein ◽  
Protein Conformations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fourier Deconvolution ◽  
Infrared Methods ◽  
Good Agreement

Fourier deconvolution has been employed to enhance the resolution of the amide I Raman band of nine proteins found in milk and/or other foods. The broad band was resolved into several components. The overall shape of the amide I Raman band of proteins was found to be nearly Gaussian or to be composed of Gaussian components. A Gaussian function was therefore used for deconvolution. The results obtained were more detailed than those obtained with the Lorentzian approximation usually employed. The resolved band components were assigned to specific protein conformations. The frequencies and assignments are in good agreement with previous Raman work based on entirely different procedures. The band areas of the resolved components appear to reflect the fraction of any given conformation in a protein. Semiquantitative estimations of protein conformation are in reasonable agreement with data obtained by x-ray diffraction and by infrared methods.

CALCULATION OF THE SELF-BROADENING OF RAMAN LINES DUE TO DIPOLAR AND QUADRUPOLAR FORCES

1963 ◽  
Vol 41 (3) ◽  
pp. 433-449 ◽  
Author(s):  
J. Van Kranendonk
Keyword(s):  
Phase Shift ◽  
Cross Sections ◽  
Scattered Light ◽  
Rotational Quantum Number ◽  
Intermolecular Forces ◽  
Intermolecular Potential ◽  
Radiation Process ◽  
Impact Theory ◽  
Order Of Magnitude ◽  
The Impact

The impact theory of Raman line broadening due to anisotropic intermolecular forces, developed previously, is applied to the broadening due to dipolar and quadrupolar forces. The optical cross sections are calculated assuming the isotropic intermolecular potential to be a hard-sphere potential, and neglecting the spread in velocities. Explicit expressions are derived for the phase-shift contribution to the width of the isotropic (j = 0) and anisotropic (j = 2) Raman scattered light as a function of the rotational quantum number J. For j = 2 scattering the phase shifts produced in the radiation do not vanish when the initial and final states of the radiation process are identical, and the phase-shift contribution to the width of the anisotropic components of the Q lines is of the same order of magnitude as for the S lines. In all cases the phase-shift contribution tends to zero when J becomes large compared with j. The contribution to the width of the inelastic collisions also tends to zero for large J, but this is characteristic of the long-range interactions considered here and results from the correspondingly short range of the resonance factors. The theory is compared with the available experimental data on H2 and N2. It is pointed out that quite generally an observation of the broadening of the isotropic and anisotropic Raman lines allows a determination of the lifetimes of the rotational levels and of the phase-shift contributions to the width of the anisotropic lines.

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