ON THE ORIGIN OF THE DIP IN THE KRF LASER GAIN SPECTRUM

High-resolution spectra of KrF (B-X) amplified spontaneous emission fr om various discharge-pumped and electron-beam-pumped KrF lasers have b een analyzed. An underlying structured absorption spectrum has been di scovered with a well-resolved peak at 248.91 nm. The absorption coeffi cient of this peak was found to vary in exact proportion to the peak l aser gain coefficient but was independent of laser gas purity. We sugg est that the absorption arises internally within the KrF molecule and is due to transitions from the B state to a higher-lying Rydberg state . This hypothesis was tested by simulating the absorption spectrum fro m KrF(B) to a weakly repulsive state dissociating to Kr*(P-3(1))+F(P- 2(3/2)). A good agreement was obtained between simulated and experimen tal absorption spectra. (C) 1996 American Institute of Physics.