부산대학교 도서관

X-ray line emission from 2{ell} - n{ell}{prime} transitions in Ne-like Kr and nearby ions has been observed from {approx} 1 {micro}m Kr clusters irradiated by fs-scale laser pulses at the JAERI facility in Kyoto, Japan. The incident laser intensity reached 10{sup 19} W/cm{sup 2}, with pulse energies from 50 to 300 mJ and pulse durations from 30 to 500 fs. The dependence of the x-ray spectral features and intensity on the incident laser intensity is rather weak, indicating that the 1 - 2 ps cluster lifetimes limit the number of ions beyond Ne-like Kr that can be produced by collisional ionization. Lines from F- to Al-like Kr emitted from the cluster plasmas have been identified using data from the relativistic multiconfiguration atomic structure code FAC. A collisional-radiative model based on this data has been constructed and used to determine that the cluster plasma has electron densities near 10{sup 22} cm{sup -3}, temperatures of a few hundred eV and hot electron fractions of a few percent.