Showing papers on "Vibrational partition function published in 1973"

Vibrational relaxation in gases and molecular lasers

Abstract: This article reviews the current status of the theory of vibrational relaxation in gases and its applications to the theory of molecular lasers. We discuss relaxation of the vibrational energy of diatomic and polyatomic molecules as represented by harmonic-oscillator models. The vibrational kinetics in a system of anharmonic oscillators is analyzed in detail. We treat quasi-steady-state population distributions of vibrational levels that arise under substantially non-equilibrium conditions, both in a singlecomponent molecular system and in gas mixtures. We discuss relaxation that proceeds in the presence of sources of vibrationally-excited molecules: infrared resonance radiation, recombination, and dissociation; in particular, we analyze the process of non-equilibrium dissociation at low gas temperatures. We discuss from a unified standpoint based on vibrational kinetics the working mechanisms of lasers using vibrational-rotational transitions in diatomic and polyatomic molecules with various means of excitation (electrical, chemical, and gas-dynamic).

Calculation of vibrational and rotational energy transfer between HF, DF, HCl, and CO2

Abstract: A theory of vibrational energy transfer which retains the exponential form of the scattering operator is applied to energy transfer between vibrationally excited HF, DF, HCl, and CO2. The calculations contain several new features, including use of curved classical trajectories and vibrational wavefunctions obtained numerically from an RKR potential. Cross sections for multiquantum pure rotational changes caused by the dipole‐quadrupole interaction are calculated. These multiquantum rotational transitions play an important role in vibrational energy exchange by allowing large vibrational energy defects to be absorbed by the rotational degrees of freedom. Agreement between theory and experiment is excellent. Cross sections calculated for simultaneous transfer of two vibrational quanta from HF or HCl to CO2 are very small. However, for DF–CO2 the calculated two‐quantum‐transfer cross section is only a factor of 2–6 smaller than that for single‐quantum transfer.

Geometry and vibrational spectra of the alkaline earth dihalides. III. MgCl2, CaCl2, SrCl2, and BaCl2

Abstract: The infrared spectra of MgCl2, CaCl2, SrCl2, and BaCl2 trapped in solid krypton matrices at 20 °K are reported. From precise measurements of changes in the vibrational modes on isotopic substitution, a linear configuration for MgCl2 and CaCl2 is confirmed and an apex angle of 120° is established for SrCl2. For BaCl2 the bond angle has been estimated at 100°. Using a valence force field we have obtained a set of force constants from the measured fundamental frequencies as well as approximate values for the anharmonic corrections to some of the vibrational modes. The statistical entropies calculated from the vibrational frequencies and molecular geometries are in excellent agreement with the thermodynamic measurements.

The vibrational Zeeman effect

Abstract: The theory of the vibrational Zeeman effect in symmetric top molecules is presented. It is shown that vibrational g factors may be related to rotational g factors and estimates are made of their magnitude for a number of molecules; these calculations indicate that vibrational Zeeman effects should be observable in symmetric top molecules in degenerate vibrational states. In addition, the novel features of the theory for linear molecules are discussed.

Vibrational relaxation of oxygen in an unsteady expansion wave

Abstract: The time‐resolved population density of the fifth vibrational level of the ground electronic state of oxygen has been obtained in an unsteady expansion wave by measuring the absorption of light at a wavelength of 2283 A. By assuming that a Boltzmann distribution exists among the vibrational degrees of freedom the vibrational temperature has been inferred and compared with those calculated for an ideally centered expansion wave based on relaxation times obtained from shock wave studies. The results suggest that the vibrational de‐excitation of oxygen proceeded at a rate agreeing with that found behind normal shock waves.