Spectral widths are reported for a high-pump power F2 excimer laser op
erating at 3-10 atm pressure. Single-shot interferograms of 1576 angst
rom radiation were produced by a vacuum ultraviolet Fabry-Perot and re
corded on film in an argon atmosphere. The 0.01-0.05 angstrom widths a
rise from population accumulation in the lower laser state commensurat
e with laser action developing on multiple rotational lines.