Visible spectral lines from n=3, {Δ}n=0 transitions in N⁺ and N²⁺ ions are used for measuring the plasma electron density and temperature in a region of two colliding blast waves, propagating through a 1.5--10-Torr nitrogen atmosphere. The blast waves originate at the tips of two aluminum rods irradiated with two beams of the Naval Research Laboratory (NRL) Pharos-III 1.054-{μ}m-wavelength Nd:glass laser operated at an energy of 200--430 J for each beam in 5-ns pulses. An electron density in the colliding-blast-wave region of Nₑ{}10¹⁸ cm^-3 was deduced from Stark broadening of spectral lines from N⁺ ions. An electron temperature of Tₑ{}4 eV was measured in this region from a spectral-line intensity ratio between N²⁺ and N⁺ ions. Near one target, an electron density of Nₑ{}8×{}10²⁰ cm^-3 was determined from series-limit x-ray spectral-line merging; a mean electron temperature of kTₑ{}225 eV was determined from x-ray line-intensity ratios. Some evidence was found for enhanced velocities for blast waves propagating through a plasma formed by a preceding blast wave.
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Elton et al. (1994) studied this question.