Berlin 2001 – wissenschaftliches Programm

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A: Atomphysik

A 5: Posters Tuesday (Photoionisation, Multi Photon Processes)

A 5.39: Poster

Dienstag, 3. April 2001, 12:30–15:00, AT3

Coherent radiation from the dense lithium vapor upon quasiresonant excitation — •Irena Labazan, Davorka Azinovic, Slobodan Milosevic, and Goran Pichler — Institute of Physics, PO Box 304 HR-10000 Zagreb, Croatia

An intense red and near-infrared radiation from lithium vapor contained in the heat-pipe oven has been observed in forward direction when the pulsed nanosecond laser was tuned near the 2p-4d resonance at 460.3 nm. To characterize this emission we have measured time resolved intensities, excitation and emission spectra near 3d-2p, 3s-2p, 4s-2p transitions versus laser intensity and density of lithium vapor, both in forward and in perpendicular direction of the laser beam. The most intense emission near 610.4 nm is observed to be slightly off-axis indicating that the main excitation is due to four-wave mixing process, which involves 4d, 4p, 3d and 2p lithium atom levels. We believe that this is the first time that such process is observed from initial level, which is the excited state. This is achieved with quasiresonant excitation where initial 2p level population goes through various molecular channels involving the leading edge of laser pulse, while the rest of the pulse excites 4d level. Other nonlinear, parametric and cooperative emission processes will be discussed.