OBSERVATION OF GAIN-NARROWING AND SATURATION BEHAVIOR IN SE X-RAY LASER LINE-PROFILES

We report on the first successful measurements of thc spectral width of an x-ray laser line. The experiments observed the 206.38-angstrom laser in Ne-like Se and indicate an unamplified width of 50 m angstrom, show gain narrowing to 10 m angstrom 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.