Laser Ionization Spectroscopy of Atomic Plasma

Abstract

This study explores the behavior of atomic inert argon (Ar) gases in a normal glow discharge under steady-state conditions using the Laser Opto-Galvanic (LOG) spectroscopic technique. A nickel hollow electrode, connected to a DC voltage source, generates plasma from Ar gases at low pressure inside a Pyrex glass tube. Tunable laser beam is then employed to perturb the steady state of the plasma species electrons, protons, ions, and excited neutral atoms through resonant absorption of the laser light. As the laser wavelength is varied, the signal profile changes over time, with both positive and negative polarity signals recorded. The study also captures spectra for one- and two-photon transitions using a boxcar averager detection system, while adjusting the delay time and gate width. Additionally, the impact of linear and circular polarization on these transitions is investigated. The goal is to present these findings in a clear and accessible way to facilitate understanding among scientists, researchers, and graduate students, promoting further research in the field. A comprehensive atlas of Ar spectral lines in the 400 to 740 nm wavelengths range are created by analyzing the visible spectrum using a pulsed tunable dye laser system. The study identifies the conditions necessary for observing two-photon lines in the optogalvanic spectrum and examines how polarized light affects the relative intensity of these lines. The temporal evolution of the optogalvanic signals is also tracked. A theoretical framework for the experimental work is provided, shedding light on the underlying mechanisms of the Opto Galvanic Effect (OGE). Finally, the study discusses the use of OGE in calibrating spectroscopic instruments, spectrum detectors, and opto-electronic devices. The technique has important applications in fields such as combustion diagnostics, isotope separation, Rydberg series analysis, micro/nanoelectronics production, and plasma physics.