Radiative lifetime of the 3s3p exp 3(exp 5 S sub 2 exp 0) metastable level of P(+)

The present experimental and theoretical results for the radiative lifetime of the 3s3p exp 3(exp 5 S sub 2 exp 0) metastable level of P(+) encompass an experimental determination of the (exp 5 S sub 2 exp 0) lifetime which represents the first measured lifetime of a low charge-state ion in the Si I sequence. This constitutes a fundamental test of the theoretical methods used to determine transition possibilities for intercombination lines involving this level, and suggests that theoretical techniques used to determine such transition probabilities in low-Z species of the Si I isoelectronic sequence should be reevaluated.