FLUORESCENCE AND SMALL-SIGNAL GAIN AT 2177 AND 2163 Å IN CIII BY RESONANT PHOTOEXCITATION WITH 310 Å, MnVI LINE RADIATION

Line radiation at 310 A from a laser-produced Mn plasma was used to resonantly photoexcite the 2s IS 4p Ip0 transition in CIII ions in a vacuum-arc discharge. Enhanced fluorescence, up to a factor of 180, was observed on the 4p-3d line at 2177 A. Enhanced fluorescence was also observed on other 4-3 lines in CIII, because the photoexcited 4p population is collisionally redistributed among all the n = 4 levels. A 72-level, collisional-radiative model of CIII was constructed, including the resonant photoexcitation. Measured values of electron density and temperature were used in the model. Theoretical predictions of enhanced fluorescence agree well with the measurements. Small-signal gain coefficients of -0.1 cm-I were theoretically predicted. Single-pass gain measurements show gains as high as 0.4 cm-l on the 4p-3d, 2177 & line and the 4f-3d, 2163 & line. This CIII-MnVI photoexcitation scheme is a prototype for soft x-ray lasers, using higher Z, isoelectronic analogs.