Abstract

This work communicates laser-plasma experiments in a gaseous mixture of hydrogen and nitrogen. Time-resolved spectroscopy measures the first four Balmer-series hydrogen lines together with selected neutral and ionized nitrogen lines. Optical breakdown plasma is generated in a 1:1 hydrogen:nitrogen mixture at ambient temperature and 0.27-atm pressure. Time-resolved spectroscopy records emitted radiation with spatial resolution along the slit height for the H ${}_{\mathsf{\alpha }}$ , H ${}_{\mathsf{\beta }}$ , H ${}_{\mathsf{\gamma }}$ , and H ${}_{\mathsf{\delta }}$ lines. For 13 selected time delays from 0.25 $\mathsf{\mu }$ s to 3.25 $\mathsf{\mu }$ s and 0.025 $\mathsf{\mu }$ s gate-widths, micro-plasma diagnostics is evaluated. Of interest are the peak separation and width of H ${}_{\mathsf{\delta }}$ and width of H ${}_{\mathsf{\gamma }}$ for electron densities in the range of 0.1 to 1.0 $\times {10}^{17}{\mathrm{cm}}^{-3}$ , and comparisons with H ${}_{\mathsf{\beta }}$ and H ${}_{\mathsf{\alpha }}$ diagnostics. Integral inversions interrogate spatial distributions of the plasma expansion. Applications include laboratory and stellar astrophysics plasma diagnosis. View Full-Text