Quenching of Einstein coefficients in plasmas

We investigate possible mechanisms for the recently observed selective quenching of spontaneous emission coefficients of carbon and nitrogen ions (C iv, C iii, and N v) in laser-produced plasmas. Various effects of the plasma electrons on the spontaneous emission of the ions are considered. We suggest (by exclusion) that the cause of the phenomenon is the weak trapping of plasma electrons by the radiating ions (producing C iii, C ii, and N iv ions in highly excited states). These highly excited electrons so strongly shift and change some low-frequency lines that they are not observed. The branching ratio of line intensities from the same upper level then becomes proportional to the fraction of ions not having any trapped electrons.