The frequency distributions of spectral lines of nonhydrogenic atoms broadened by local Gelds of both electrons and ions in a plasma are calculated in the classical path approximation. The electron collisions are treated by an impact theory which takes into account deviations from adiabaticity. For the ion e6ects, the adiabatic approximation can be used to describe the time-dependent wave functions. The various approximations employed were examined for self-consistency, and an accuracy of about 20% in the resulting line profiles is expected. Good agreement with Wulff's experimental helium line profiles was obtained while there are large deviations from the adiabatic theory, especially for the line shifts. Asymptotic distributions for the line wings are given for astrophysical applications. Here the ion eKects can be as important as the electron effects and lead to large asymmetries, but near the line core electrons usually dominate. Numerical results are tabulated for 24 neutral helium lines with principal quantum numbers up to five.

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A theory of line broadening in the impact approximation is developed which includes the case of overlapping lines. It is assumed that the collisions which give rise to the broadening do not cause transitions between states with different principal quantum numbers. The theory has been worked out in detail in two cases:(1) the broadening arises only from perturbations of the upper state with arbitrary splitting of the substates. This approximation may be used if the perturbations of the lower state are relatively unimportant (e.g., the higher series members of the Balmer lines), and is exact if the perturbations do not affect the lower state as in the case of the ground state of hydrogen perturbed by electron collisions; (2) complete degeneracy of the initial and final states. This approximation is also valid on the far wing of the line if there is splitting, i.e., for frequencies large compared to the splitting, and is a generalization of Anderson's theory. The formal theory is worked out by two different methods. The method of calculation for nearly degenerate initial and final states with splitting is indicated. Method I is particularly suited for calculating the wing distribution while Method II is more suitable for finding the intensity distribution at the line center for overlapping lines. The line profile is made up of a sum of dispersion profiles and asymmetric terms which arise from interferences when the transition operator is not diagonal. The shift and half-width parameters are found from the roots of a secular equation and depend on the splitting as well as the density, temperature, and the character of the perturbation.

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It is shown that laser action at 3371 A terminates in times t < (tau(32)(-1) + Y(3))(-1), where tau(32) is the lifetime of the transition of C(3)pi(u) --> B(3)pi(g) and Y(3) is the electron depopulation rate of the upper laser level. Following Gerry but including electron impact mixing of laser levels, rate equations, coupled to the circuit equation, were solved under saturation approximations. Assuming a Seaton excitation cross section between laser levels, with an effective Gaunt factor of 0.25, power and pulse width were in good agreement with Shipman's values. The rate equations were also solved without recourse to the saturation approximation yielding excellent agreement with the saturation method during most of the pulse and indicating the existence of an early oscillation which is not predicted by the saturation approximation method. Finally, the inclusion of the electron impact ionization of he nitrogen molecule from the excited state C(3)pi(u) brings the pulse width to still better agreement with Shipman's values.