FIZIKA A 7 (1998) 4, 205 - 212

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and H.-J. KUNZEd

aUniversity of Zagreb, Faculty of Electrical Engineering and Computing,
Division of Applied Physics, Unska 3, 10000 Zagreb, Croatia

bRudjer Bo sković Institute, Dept. of Material Science, Thin Films Laboratory,
Bijenička 54, 10000 Zagreb, Croatia

cUniversity of Zagreb, Faculty of Science, Dept. of Physics, Bijenička 32,
10000 Zagreb, Croatia

dRuhr Universität Bochum, Institut für Experimentalphysik V,
44780 Bochum, Germany

Received 29 October 1998; revised manuscript received 22 January 1999
Accepted 8 February 1999

The ultraviolet and visible spectra of plasmas produced by N2-laser radiation focused onto a copper target in air and in vacuum have been recorded photographically. The nitrogen laser beam (l = 337 nm) had a maximum energy density of 1.1 J/cm2, the pulse duration was 6 ns, and the repetition rate 0.2 Hz. The measured electron temperature was 15000 K (±30%) in air and 13000 K (±50%) in vacuum and the electron densities were 6.5×1017 cm-3 (±60%) and 3.0×1017 cm-3 (±60%), respectively. The irradiated surface in air and in vacuum was studied employing a metallographic microscope. In vacuum, the droplets were created and expulsed at the crater edges. Their formation is explained by the hydrodynamical model. They were formed in a time interval which is about two times shorter than the duration of the laser pulse. In air, droplets were also formed. The weight loss from the Cu-crater in vacuum was about 0.3×10-4 mmole/pulse, in air it was about three times less.

PACS numbers: 52.50.Jm, 61.80.Ba
UDC 533.9

Keywords: laser-induced plasma, N2-laser radiation, short pulses, copper surface
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