J. Phys. IV France 11 (2001) Pr2-433-Pr2-436
Interaction of intense, femtosecond laser pulse with small-sized Ne clustersT. Mocek1, 2, C.M. Kim1, H.J. Shin1, D.G. Lee1, Y.H. Cha1, K.H. Hong1 and C.H. Nam1
1 Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Kusong-dong, Yusong-gu, Taejon 305-701, Korea
2 Department of Gas Lasers, Institute of Physics, Na Slovance 2, 18221 Prague 8,Czech Republic
We report the first observation of X-ray emission (4 - 18 nm) from small-sized Ne clusters heated by high-intensity, 25-100 fs laser pulses. The Ne spectrum started to drastically change in emitting ions from Ne5+ to Ne7+ below the pre-expansion temperature of -120 °C. The significant change in the spectrum is attributed to the collisional heating of small-sized Ne clusters formed in the cryogenically cooled gas jet. Though the size of Ne clusters in our experiment is estimated to be quite small, i.e. a few tens of atoms per cluster, and thus they were undetectable by the standard Rayleigh scattering technique, the appearance of spectral lines of Ne7+ ions presented clear evidence of collisional heating that occurred in near-solid-density cluster. By extending the laser pulse length from 25 fs to 100 fs, considerably higher X-ray yield from the highest charge state Ne7+ was observed in the covered spectral region, showing more efficient absorption of 100 fs laser pulse.
© EDP Sciences 2001