Measurements of Gaseous Hydrogen–Nitrogen Laser-Plasma

Christian G Parigger

doi:10.3390/atoms7030061

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 α , H β , H γ , and H δ lines. For 13 selected time delays from 0.25 μ s to 3.25 μ s and 0.025 μ s gate-widths, micro-plasma diagnostics is evaluated. Of interest are the peak separation and width of H δ and width of H γ for electron densities in the range of 0.1 to 1.0 × 10 17 cm - 3 , and comparisons with H β and H α diagnostics. Integral inversions interrogate spatial distributions of the plasma expansion. Applications include laboratory and stellar astrophysics plasma diagnosis.

Highlights

Measurement of laser-plasma has gained significant attention in recent years [1,2]
Plasma characteristics for time delays up to 0.275 μs were previously discussed for exclusively hydrogen gas at 0.75 atm and ambient temperature [9,10,11]
The experimental study of Hγ and Hδ line shapes shows that results are obtained that are consistent with those from Hα and Hβ, especially for time delays of the order of a few μs after initiation of laser-plasma: Shock waves tend to propagate at speeds of the order of one mm/μs for the 0.27-atm hydrogen–nitrogen mixture

Summary

Introduction

Measurement of laser-plasma has gained significant attention in recent years [1,2]. Addition of fractionally small amounts of hydrogen [5] can be vital for analysis of plasma. Time-resolved plasma spectroscopy [6,7] requires spatial resolution for appropriate characterization of expansion phenomena and species distributions. Recent hydrogen laser-plasma experiments address the first four Balmer-series hydrogen lines—early in the plasma decay, neutral and ionized nitrogen lines are identified and appear first as the plasma cools. Plasma characteristics for time delays up to 0.275 μs were previously discussed for exclusively hydrogen gas at 0.75 atm and ambient temperature [9,10,11]. Optical breakdown plasma is generated in a 1:1 hydrogen:nitrogen mixture at ambient temperature and

Methods

Results

Conclusion