VIBRATIONAL FREQUENCY PERTURBATIONS IN THE RAMAN SPECTRUM OF HYDROGEN

1965 ◽  
Vol 43 (10) ◽  
pp. 1836-1842 ◽  
Author(s):  
A. D. May ◽  
J. D. Poll
Keyword(s):  
Raman Spectrum ◽  
Vibrational Frequency ◽  
Adiabatic Approximation ◽  
Intermolecular Forces ◽  
Solid Hydrogen ◽  
Hydrogen Gas ◽  
Lattice Vibrations

The influence of the lattice vibrations on the shift of the vibrational Raman lines in solid hydrogen and the influence of nonadditive intermolecular forces on the shift in hydrogen gas are investigated for freely rotating molecules in terms of the adiabatic approximation. It is shown that the experimental value for the shift in the solid (Soots et al. 1965) can be accounted for by introducing a reasonable value for the amplitude of the lattice vibrations. The effect of the nonadditive intermolecular forces on the shift in hydrogen gas is shown to be appreciable at high densities.

The Raman spectrum of solid hydrogen

1965 ◽  
Vol 26 (11) ◽  
pp. 615-620 ◽  
Author(s):  
E.J. Allin ◽  
A.H. M ◽  
V. Soots ◽  
H.L. Welsh
Keyword(s):  
Raman Spectrum ◽  
Solid Hydrogen

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.

THEORY OF THE INTERACTION BETWEEN THE LATTICE VIBRATIONS AND THE ROTATIONAL MOTION IN SOLID HYDROGEN

1966 ◽  
Vol 44 (2) ◽  
pp. 313-335 ◽  
Author(s):  
J. Van Kranendonk ◽  
V. F. Sears
Keyword(s):  
Rotational Motion ◽  
Zero Point ◽  
Solid Hydrogen ◽  
The Self ◽  
Intermolecular Potential ◽  
Lattice Vibrations ◽  
Energy Effect ◽  
Self Energy ◽  
Blowing Up ◽  
Point Lattice

The effects of the interaction between the rotational motion of the molecules in solid hydrogen and the lattice vibrations, resulting from the anisotropic van der Waals forces, have been investigated theoretically. For the radial part of the anisotropic intermolecular potential an exp–6 model has been adopted. First, the effect of the lattice vibrations, and of the anistropic blowing up of the crystal by the zero-point lattice vibrations, is discussed. The effective anisotropic interaction resulting from averaging the instantaneous interaction over the lattice vibrations is calculated by assuming a Gaussian distribution for the modulation of the relative intermolecular separations by the lattice vibrations. Secondly, the displacement of the rotational levels due to the self-energy of the molecules in the lattice is calculated both classically and quantum mechanically, and the resulting shifts in the frequencies of the rotational transitions in solid hydrogen are given. Finally, the splitting of the rotational levels due to the anisotropy of the self-energy effect is calculated. The theory is applied to the calculation of the asymmetry of the S0(0) triplet in the rotational Raman spectrum of solid parahydrogen, and of the specific heat anomaly in solid hydrogen at low ortho-concentrations.

The single crystal Raman spectrum of orthorhombic PbCl2

1970 ◽  
Vol 48 (18) ◽  
pp. 2931-2933 ◽  
Author(s):  
G. A. Ozin
Keyword(s):  
Raman Spectrum ◽  
Raman Scattering ◽  
Single Crystal ◽  
Lattice Vibrations ◽  
Polarized Raman ◽  
Oriented Single Crystal

The frequencies and symmetries of the even parity lattice vibrations of orthorhombic lead dichloride are determined by means of polarized Raman scattering from an oriented single crystal. The frequencies of the vibrations are interpreted in terms of symmetry co-ordinates and by comparison with the modes of the isomorphous lead dibromide.

DENSITY EFFECTS IN THE RAMAN SPECTRUM OF CARBON DIOXIDE

1952 ◽  
Vol 30 (2) ◽  
pp. 99-110 ◽  
Author(s):  
H. L. Welsh ◽  
P. E. Pashler ◽  
B. P. Stoicheff
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Raman Spectrum ◽  
Relative Intensity ◽  
Intermolecular Forces ◽  
Anisotropic Scattering ◽  
Fermi Resonance ◽  
Intensity Effect ◽  
Density Effects ◽  
Frequency Changes

Two Raman tubes, one of quartz and one of glass, capable of withstanding pressures up to 75 and 300 atm. respectively, were used to study density effects in the Raman spectrum of carbon dioxide. The components of the ν1 band show changes in frequency and relative intensity with increasing density. An analysis shows that the frequency changes are due to a lowering of the frequency of 2ν2, in Fermi resonance with ν1, with increasing density. The intensity effect, however, is not completely explained by the change in the sharpness of the resonance. In the high pressure gas and in the liquid faint bands corresponding to the Raman inactive frequencies, ν2 and ν3, are observed. The effect of increasing density on the rotational Raman spectrum can be explained in terms of the broadening of anisotropic scattering by intermolecular forces.

Raman Spectrum of Gypsum

1971 ◽  
Vol 49 (7) ◽  
pp. 885-896 ◽  
Author(s):  
N. Krishnamurthy ◽  
V. Soots
Keyword(s):  
Hydrogen Bond ◽  
Raman Spectrum ◽  
Water Molecule ◽  
Laser Excitation ◽  
Lattice Vibrations ◽  
Principal Moments Of Inertia ◽  
Lattice Modes ◽  
Bond Vibration ◽  
Oriented Single Crystal ◽  
Combination Frequencies

The Raman spectrum of an oriented single crystal of CaSO4∙2H2O has been recorded from 20 to 3600 cm−1 at 300 °K and 77 °K using polarized laser excitation. The symmetries of the observed Raman lines have been determined and the spectrum has been analyzed in terms of external lattice vibrations, internal vibrations of the SO4 and H2O groups, hydrogen bond vibrations, and combinations of these vibrations. The translatory and rotatory lattice modes of the H2O molecules have been identified and the latter have been correlated with the principal moments of inertia of the water molecule. The hydrogen bond vibration was observed at 210 cm−1 at 300 °K and 217 cm−1 at 77 °K. The assignments of the internal modes were found to be consistent with the results of previous workers. Several overtone and combination frequencies were observed, especially in the region of the ν1 and ν3 vibrations of H2O.

Theory of the interaction of the lattice vibrations with the vibrational excitations in solid hydrogen

1970 ◽  
Vol 48 (5) ◽  
pp. 489-501 ◽  
Author(s):  
J. Noolandi ◽  
J. Van Kranendonk
Keyword(s):  
Solid Hydrogen ◽  
The Self ◽  
Order Perturbation ◽  
Lattice Vibrations ◽  
Phonon Coupling ◽  
Phonon Interaction ◽  
Self Consistent ◽  
Vibrational Excitations ◽  
Intramolecular Vibrations ◽  
Quantum Crystals

The theory of the interaction of the vibrational excitations (vibrons) with the lattice vibrations in solid hydrogen is developed. The phonons are treated in the self-consistent harmonic (SCH) approximation appropriate to quantum crystals. The vibron–phonon interaction is expanded in terms of the SCH phonon operators rather than in powers of the displacements of the molecules from their equilibrium positions. First- and second-order perturbation corrections to the vibron energies arising from the vibron–phonon coupling are calculated. The effect of the anharmonicity of the intramolecular vibrations in conjunction with the vibron–phonon coupling is also discussed.

Fundamental and Overtone Vibrational Transitions in the Raman Spectrum of h.c.p. Solid Hydrogen

1972 ◽  
Vol 50 (13) ◽  
pp. 1471-1479 ◽  
Author(s):  
William R. C. Prior ◽  
Elizabeth J. Allin
Keyword(s):  
Raman Spectrum ◽  
Relative Intensity ◽  
Argon Laser ◽  
Solid Hydrogen ◽  
Frequency Separation ◽  
Frequency Change ◽  
Quadrupolar Interaction ◽  
Vibrational Coupling ◽  
Frequency Shifts ◽  
Vibrational Overtone

The use of an argon laser of high intensity has made it possible to observe the vibrational overtone of solid hydrogen and to study the fundamental over a wider concentration range than previously. At ortho concentrations below ~ 15% the Q1(1) line has two components. The dependence on concentration and temperature of the frequency separation and relative intensity of these components is accounted for by the quadrupolar interaction between ortho molecules. Differences in the frequency shifts of the Q1(0) and the Q1(1) and of the Q2(0) and the Q1(1) lines in mixtures of all concentrations are also related to the quadrupolar interactions. The overtone lines show almost no frequency change with concentration. This is explained by a much smaller vibrational coupling due to the isotropic interactions in the ν = 2 than in the ν = 1 state. Confirmation of this is found in the small enhancement of the intensity of Q2(1) relative to Q2(0). The measurement of the frequency of Q2(0) makes it possible to determine the parameters μ1, and μ2, specifying the change in the intramolecular potential by the isotropic interactions, from transitions involving J = 0 states alone.

Raman spectrum of solid hydrogen deuteride

1993 ◽  
Vol 47 (22) ◽  
pp. 14886-14897 ◽  
Author(s):  
J. J. Miller ◽  
R. L. Brooks ◽  
J. L. Hunt
Keyword(s):  
Raman Spectrum ◽  
Solid Hydrogen ◽  
Hydrogen Deuteride
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