Investigation on effects of quenching of Einstein A coefficient in plasmas

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1) In order to investigate the claim : Quenching of Einstein A Coefficient in Plasmas which has been proposed by the Princeton Univ.group, we tried to measure the branching ratios of He I np^3P-2s^3S, 3s^3S (n=6,7,8,9,10) in low density plasmas (ne<10^<14> cm^<-3>), which enables us to measure the total line intensities without the problem of Stark broadening. Here, we used nonequilibrium recombining plasma, in order to observe the transitions from highly excited states.As the result, changes of branching ratios up to 50% were observed. However, this result may not be directly attributed to the quenching spontaneous transition probabilities caused by the quantum electromagnetic effect. At present, an effect of level mixing at highly excited states is a candidate for a possbile mechanism on the changes of branching ratio.2) According to a branching ratio between multiplet structures, it is generally demonstrated that the atomic branching ratio is a constant and does not depend on the population distribution among the upper sublevels, if the structures of lower levels are same.