The X-ray spectra of H-like, He-like and Li-like silicon ions after foil excitation

Radiation emitted from silicon beams at 35, 38 and 45 MeV excited by passage through thin carbon foils has been studied in the range 3-9 AA using a curved-crystal X-ray spectrometer. More than 100 lines have been observed, of which only one quarter had been observed or predicted from solar or laboratory plasma spectra. Most of the previously unobserved lines may be attributed to satellites of H- and He-like transitions arising in three- and four-electron Si ions. The lifetime of the Si XIII 2 3 P 1 state has been measured, and a preliminary experimental value of 6.5+or-1.3 ps obtained.