Kwang Yul Kim

Observation of Modulations in Lyman‐Alpha Line Profiles of Hydrogen‐Like Ions of Oxygen in Clusters Irradiated by Femtosecond Laser Pulses: Effect of an Oscillatory Electric Field

Profiles of the Lyα line of O VIII ions in N2O clusters irradiated by femtosecond laser pulses (laser flux up to 4×1017 W/cm2) were recorded. The features (peaks and dips) in the Lyα O VIII line profiles were observed evidencing the presence of intense plasma oscillations with an amplitude of the electric field E0 ∼ (0.5 – 1.0) × 109 V/cm and a frequency ω ∼ (0.7 – 2.4) × 1015 s−1.

Observation and Analysis of Strong Oscillating Electric Fields in a ps and fs Laser Plasma by High-resolution X-ray Spectroscopy Measurements

The results of measurements of the multicharged ions spectra in plasma produced by moderately intense (up to 4×1017 W/cm−2) laser pulses are presented. In the first case, Nd glass laser radiation with energy 1 – 2 J and pulse duration 1.5 ps was focused on the flat solid Teflon target. In the second case, Ti:Sa laser radiation with energy ∼70 mJ and pulse duration 70 and 500 fs was focused onto an N2O gas jet, created by a high‐pressure liquid nitrogen cooled, pulsed (10 Hz) nozzle. Profiles of the Lyα lines of F IX ions in Teflon target and O VIII ions in N2O clusters were recorded with a very high spectral resolution λ/δλ ∼ 3000 – 5000. The features (peaks and dips) in the Lyα line profiles were observed. They suggest the existence of intense plasma oscillations with a frequency appreciably lower than the frequency of the laser radiation. The observed X‐ray spectra for the plasma satellites of the Lyα doublet of the hydrogen F IX and O VIII ions in plasma were modeled theoretically. It was shown that th...