engleski

Quasiresonant excitation of lithium vapor

Quasiresonant laser excitation offers an interesting way to produce highly excited atoms in a vapor mixture. It is generally a process in which laser photon absorption starts from an excited atomic level. The initial excited atomic level population is obtained through the accidental resonance with molecular transitions followed by various processes such as collisionally or radiatively induced dissociation or energy transfer. In the Li+Li2 system, the quasiresonant excitation has not been studied in details, but was used in laser-induced plasma experiments [1,2]. In this work we performed quasiresonant laser excitation of pure lithium vapor and Li-Cd vapor mixtures at 460.3 nm (2p-4d) and 497.2 nm (2p-4s). The initial population of Li(2p) level is caused by three processes: collisional dissociation or photodissociation of the Li2 B1Pu molecules or energy transfer in Li2 (B1Pu) and Li(2s) collisions. The Li(4d,4s) atoms radiatively decay towards Li(3p), from which collisional population transfer to Cd(53PJ) occurs, followed by three-body reactive collisions which produce the LiCd(2 2P ) excimer states [3]. We have used absorption spectroscopy and selective wavelength excitation spectroscopy to study line shapes of the relevant resonances and obtain detials of the excitation processes. Experimental results are suported with detailed spectral simulations. 1. J. T. Bahns, M. Koch, W. C. Stwalley, ''Physics of Ionized Gases''. (Edited by. L. Tanovic, N. Konjevic and N. Tanovic) (Nova Science Publishers, New York 1989), p. 503. 2. A. C. Tam and W. Happer, Opt. Commun. 21, 403 (1977). 3. S. Milosevic, D. Azinovic, I. Labazan and G. Pichler, Physica Scripta, in press (2000).

quasiresonant excitation; lithium vapor; laser spectroscopy

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