Lifetime measurements of the1P1state of helium-like Si and Cl

K X-rays, produced by foil excitation of 48.5 MeV Cl and 47 MeV Si beams, were studied using a high resolution Doppler-tuned spectrometer. From observation of the X-ray yield at the foil as a function of target thickness, the lifetimes of the 1 P 1 state of helium-like Cl and Si were deduced to be 0.9+or-0.2*10 -14 s and 2.9+or-1.0*10 -14 s respectively.