The Role of 6p States of Xe in the Discharge Pumped XeCl Laser Emission

M Castillejo,J J Medina,I García-Moreno,J M Figuera

doi:10.1155/lc.12.13

Abstract

The role played by 6p metastable Xe level in the kinetics of discharge pumped XeCl laser emission is investigated by performing time resolved and time integrated fluorescence studies of the Xe 6p–6s emissions produced in the discharge plasma at various pressures of chlorine donor compounds. The results analyzed according to a simple kinetic model suggest that 6p level is populated through a cascading mechanism involving various Xe levels which is enhanced by the presence of the halogen donor compound. The laser emission dependence is also investigated as a function of the halogen donor pressure. The observations lead to the conclusion that 6p states do not play a relevant role in the formation of XeCl* molecules and that other Xe excited states should be considered to account for the participation of the neutral channel in the XeCl* formation mechanism.

Highlights

Despite the importance of excimer lasers in many areas of research and industry, the complicated kinetics of the processes occurring in the laser plasma is still not without uncertainties
In the last few years a number of publications dealing with XeCI* laser models2’3 and spectroscopic investigations of Xe excited-state density have appeared.’-6 As a result of these studies it has become evident that highly excited Xe metastables are necessary to understand the neutral channel formation kinetics of the XeC1 laser gas mixtures both pumped by electrical discharges and by electron beams
The discussion is centered around the role of excited state kinetics which in the past has been assumed to be less important in XeC1 than in other rare-gas halide lasers, such as KrF and has been considered to be of secondary importance as compared to formation of XeCI* through Xe /--C1

Summary

INTRODUCTION

Despite the importance of excimer lasers in many areas of research and industry, the complicated kinetics of the processes occurring in the laser plasma is still not without uncertainties. In the last few years a number of publications dealing with XeCI* laser models2’3 and spectroscopic investigations of Xe excited-state density have appeared.’-6 As a result of these studies it has become evident that highly excited Xe metastables are necessary to understand the neutral channel formation kinetics of the XeC1 laser gas mixtures both pumped by electrical discharges and by electron beams. Time integrated and time resolved fluorescence studies of 6p-6s transitions occurring in the UV preionized discharge plasma were carried out using different halogen donor compounds. All measurements in the present study were made for a base gas mixture of He/Xe (3.2 bar/45 mbar) to which different pressures of various halogen donor compounds were added. 2. Time resolved and time integrated fluorescence studies of the different rare gas/halogen donor mixtures. Time resolved and time integrated fluorescence studies of the different rare gas/halogen donor mixtures For these experiments the fluorescence light was observed at a fixed wavelength selected with the monochromator. The halogen donor compounds were used as supplied, after degassificao tion in the case of vapours and their purity is as stated: Cl2 99.8%, HC1 99.99%, CH2C12 99.6%, CHC13 99.8%

Emission Spectra

Fluorescence Decay Curves

Laser Emission