Observation of enhanced soft x-ray emission using nitrogen clusters ionized by intense, femtosecond laser

Abstract

We report soft x-ray spectra (5-18 nm) from a cryogenically cooled nitrogen gas jet irradiated by 28-fs-laser pulses at an intensity of similar to7 x 10(16) W/cm(2). While the time-integrated spectrum obtained at room temperature showed exclusively transitions in N4+ ions, spectral lines from N5+ and N6+ charge states appeared with cooling. Rapid, nonlinear increase of x-ray emission on lines from N4+, N5+, and N6+ has been observed by lowering the preexpansion gas temperature. (C) 2003 American Institute of Physics.