Delayed emission of 2p-1s and 3p-1s X-rays from 40 MeV neon ions ionized in a thin carbon foil

A previous study of the He- and H-like lines of 40 MeV Ne projectiles excited by a thin carbon foil showed that the x-ray spectrum contains only He-like and H-like lines and that the intensities of these lines are sufficient to employ a high resolution curved crystal spectrometer to study the decay curves for individual transitions. Presented are Ne K x-ray spectra excited by passing a beam of 40 MeV ions through a 50 μg/cm2 carbon foil. They were taken at 0, 2.3, and 9.1 mm behind the foil and are normalized to the same total integrated charge in the carbon foil. The 1s2p(23P1)-1s2(11S0) transition is a spin-forbidden, metastable, intercombination line and has a lifetime of 1.85 x 10-10 sec8, whereas the He-like 1s2p(1P)-1s2(1S), H-like 2p(2P)-1s(2S), and H-like 3p(2P)-1s(2s) transitions are dipole-allowed with lifetimes of 1.13 x 10-13 sec8, 1.59 x 10-13 sec9, and 5.98 x 10-13 sec 10, respectively. It is apparent that even at 1 cm (i.e. 0.5 ns) behind the foil, considerable intensity is still detected for the short lifetime transitions indicating that electrons are cascading from very high n levels. Previous measurements and calculations have shown that the decay curves can be described by a power law of the form I = ct/sup -b/, where c and b are constants for a given line. It has been found that b depends on the initial n,l distribution. The measured decay curves for the delayed He-Like 1s2p(1P)-1s2(1S), H-like 2p-1s and H-like 3p-1s transitions are shown fitted to this power law