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Author Yao, X. ♦ Kumar, D. ♦ McGlynn, S. P.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword PLASMA PHYSICS AND FUSION ♦ TRANSIENTS ♦ PLASMA ♦ NEON ♦ HIGH-FREQUENCY DISCHARGES ♦ ENERGY-LEVEL TRANSITIONS ♦ LASER RADIATION ♦ EXCITATION ♦ METASTABLE STATES ♦ IMPEDANCE ♦ IONIZATION
Abstract The optogalvanic effects (OGE) induced by pulsed laser excitation of Ne 1s{sub 2,4}{r_arrow}2p{sub 1,3} transitions in a low power, {approximately}30 MHz radio frequency Ne discharge at {approximately}5 Torr are described. The polarity (sign) of the OGE signal is controlled by perturbations of the 1s{sub j} populations. The steady state 1s{sub 4} population is {approximately}10{sup 1} times larger than the 1s{sub 2} population and the OGE signals for 1s{sub 4}{r_arrow}2p{sub 1,3} excitations are correspondingly stronger than those for 1s{sub 2}{r_arrow}2p{sub 1,3} excitations. The plasma temperature is found to be {approximately}1000 K. The excitations 1s{sub 2,4}{r_arrow}2p{sub 3} are more efficient at signal production than the 1s{sub 2,4}{r_arrow}2p{sub 1} excitations, which is contrary to prediction. The OGE signals are consequences of: (1) perturbation and reequilibration of the metastable 1s{sub 3} and 1s{sub 5} populations; (2) radiatively trapped 1s{sub 2}{r_arrow}{sup 1}S{sub 0} photons; and (3) collisionally induced 1s{sub 2}, 1s{sub 4}{leftrightarrow}1s{sub 3}, 1s{sub 5} energy transfer. The OGE signal components, both the ionization and photoacoustic constituents, are temporally coincident only when the immediate causative agents are trapped photons. When otherwise produced, the photoacoustic part is delayed relative to the ionization component by the time required for the acoustic wave to travel from the locus of excitation to the sensitive region(s) of the plasma. {copyright} {ital 1999 American Institute of Physics.}
ISSN 00218979
Educational Use Research
Learning Resource Type Article
Publisher Date 1999-03-01
Publisher Place United States
Journal Journal of Applied Physics
Volume Number 85
Issue Number 6


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