Observation of gain-narrowing and saturation behavior in Se X-ray laser line profiles

The first successful measurements of the spectral width of an X-ray laser line are reported. The experiments observed the 206.38-A laser in Ne-like Se and indicate an unamplified width of 50 mA, show gain narrowing to 10 mA in intermediate length amplifiers, and show no significant rebroadening in saturated amplifiers. The unamplified width is 1.4 times the expected Doppler width, and the lack of rebroadening leads to speculation that collisional effects may play a significant role in determining the line profiles. (Author)