Inner-shell X-ray emission from high contrast femtosecond-pulse laser irradiation of Ar clusters; Observation and modeling

Colgan, J.*; Abdallah, J. Jr.*; Faenov, A.*; Pikuz, T.; Skobelev, I.*; 福田 祐仁; 林 由紀雄; Pirozhkov, A. S.; 川瀬 啓悟*; 桐山 博光; et al.

no journal, , 

A study is made of the ultra short laser pulse irradiation of Ar cluster targets. Experiments have been performed with large cluster sizes and using very high laser contrasts, which have allowed clear and unambiguous observation of exotic inner shell transitions in near neutral Ar ions, so called hollow atom transitions. The interaction of the main laser pulse with the unperturbed target is a necessary requirement for observing these lines. Our measurements are supported by kinetics calculations in which a very detailed atomic model is used. The Los Alamos suite of atomic structure and kinetics codes is used to perform the modeling. The calculations predict all of the spectral features found experimentally, and support the notion that the X-ray emission arises from many ion stages of the Ar plasma, from near neutral through He like ions, and from a range of plasma temperatures and densities.