A wavelength-selective feedback modulation scheme was devised to study the competitive behavior of the lasering transitions in the argon ion laser and to determine the coupling relationships, radiative as well as collisional, between the inverted states of the ion. By means of monitoring cross modulation on lasering lines, spontaneous transitions, and discharge current, the interdependence of the lasering transitions was determined. Whereas lasering transitions which share common energy levels, upper or lower, are expected to compete adversely with each other, it was found that under certain conditions the contrary takes place.

The electron‐ion recombination coefficient αei in ionized nitrogen gas is investigated as to its variation with pressure (0.2 to 2 mm Hg) and electron temperature (92°K to 300°K) corresponding to various low electron energies. At 1.3 mm Hg, αei varies from about 8.5×10−7 cm3/sec at 300°K to 6.7×10−6 cm3/sec at 92°K, almost an order of magnitude difference. Discussion of the possible modes of recombination in a nitrogen gas plasma is given and dissociative recombination is found to be the most probable means of electron loss. Microwave transmission methods were used in this study.

Vacuum ultraviolet instrumentation compatible with simultaneous operation of the argon ion laser is described and perturbation spectroscopy on the resonance transitions of the argon ion is reported. Observations suggest a largely nonradiative destruction of the lower levels of the lasering transitions at current densities up to 300 A cm−2 and within a pressure range of 0.1 to 0.5 Torr.

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A detailed temporal history of the electron density on the axis of a theta pinch is presented. During the magnetic compression, oscillations are superimposed on the electron density. The amplitude of these oscillations is, under some conditions, as large as 50% of the maximum value attained in the pinched state. These density variations are ascribed to radial hydromagnetic oscillations. The electron density measurements were made by means of a spherical laser interferometer and these were correlated with electron density measurements using Stark broadening techniques.