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Measurements of the free-free absorption coefficient in high-pressure (50–400 psia) e-beam-excited rare-gas plasmas have been used to deduce the temporal evolution of electron density in these systems. The measurements were carried out using a focused CO2 laser beam passing through the excited region of the plasma. Comparison of theory and experiment in the early afterglow, where Penning ionization of excimers dominates the electron production, yields a room-temperature rate coefficient of 8×10−11 cm3/sec for this process in xenon.

The dynamic behavior of the high-pressure rare-gas VUV excimer systems is examined. It is found that the collisional coupling of the excited singlet and triplet manifolds in combination with the losses arising from photoionization play a vital role in determining the over-all performance. The proposed mechanisms provide a unified description of both the pressure dependence of the stimulated output and the observed pressure shift of the stimulated spectrum in xenon. Numerical values of the relevant parameters are given.

The peak electron density in e-beam-excited rare-gas plasmas has been studied as a function of pressure, using inverse bremsstrahlung absorption techniques. It was found that the heavier rare gases exhibit broad maxima beyond which the peak electron density decreases monotonically with pressure. No maxima were observed in helium or neon over the pressure range investigated (0–400 psia). Data are presented along with a proposed theoretical explanation for the observed phenomena.