Optimization of C5+ Balmer-α line intensity at 182 A from laser-produced carbon plasma

Parametric dependence of the intensity of 182 angstrom Balmer-alpha line (C5+ ; n = 3 -> 2), relevant to xuv soft X-ray lasing schemes, from laser-produced carbon plasma is studied in circular spot focusing geometry using a flat field grating spectrograph. The maximum spectral intensity for this line in space integrated mode occurred at a laser intensity of 1.2 x 10(13) W cm(-2). At this laser intensity, the space resolved measurements show that the spectral intensity of this line peaks at similar to 1.5 mm from the target surface indicating the maximum population of C5+ ions (n = 3), at this distance. From a comparison of spatial intensity variation of this line with that of C5+ Ly-alpha (n = -> 1) line, it is inferred that n = 3 state of C5+ ions is predominantly populated through three-body recombination pumping of C6+ ions of the expanding plasma consistent with quantitative estimates on recombination rates of different processes.