The asymptotic line wing theory assumes the presence of two intermolecular interaction characteristics–quantum and classical intermolecular interaction potentials–in the expression of the absorption coefficient. The same classical potential enters into the expression for the second virial coefficient. The classical potential found from the second virial coefficient data is used for calculating of the temperature dependence of the absorption coefficient of water vapor line wings in the 8–12 μm transparency window. To obtain agreement between the calculated and experimental absorption coefficients at this point, it is necessary to refine the expression for the absorption coefficient by abandoning the longwave approximation in line wings. The calculation that meets this condition is performed in the framework of a diffusion model. The time between collisions of certain type giving rise to line wing absorption is estimated. © 2012 Wiley Periodicals, Inc.

The self-broadened H 2 O continuum absorption data for the 3−5 μm window available in the literature are described in the framework of asymptotic line wing theory. Use is made of a diffusion model taking into account violation of the long-wave approximation in spectral line wings.

Dynamics and radiation of a relativistic charged particle moving in a linear restoring force field is studied. Solutions to the equations of motion are presented in a compact form in terms of Jacobi elliptic functions. The intensity of radiation, its angular distribution and radiation spectrum of a relativistic oscillator are investigated. It is shown that, unlike a non-relativistic oscillator, the maximum intensity is emitted not at the turning points, but at some intermediate points of the particle's trajectory. The emission spectrum consists of lines at frequencies that are multiples of the oscillation frequency of the oscillator. As the oscillator energy increases, the number of harmonics in the spectrum increases. The maximum in the spectrum of highly relativistic oscillator occurs on high numbers of harmonics.