Spectroscopy of hard X-rays (2-15 keV) generated by focusing femtosecond laser on metal targets

Spectroscopy of hard X-rays generated by focusing a femtosecond laser (42 f s at 780 nm) onto metal targets consisting elements of various atomic numbe r (Z) is carried out in the energy range between 2 and 15 keV using a direc t-detection charge-coupled-device camera. Sharp K-shell line emissions are observed fur X-rays generated from medium-Z targets (Til Fe, Ni, Cu and Zn) , which can be used for X-ray diffraction without further monochromization. A blond continuum and a weak trace of L-shell line emissions are observed fur X-rays from high-Z targets (Mo, Nb and W). The energies of the characte ristic X-rays agree well with that of X-rays from neutral atoms or slightly ionized ions.