We present the observation of solid material luminescence excited by s
oft x-ray laser. The 21.2 nm photons of the soft x-ray laser of the La
boratoire d'Utilisation des Lasers Intenses (Palaiseau, France) have b
een used to induce ultraviolet luminescence in CsCl and CsI. The laser
supplied up to 6x10(12) photons in 80 ps. A single laser shot was suf
ficient to obtain luminescence spectra with very good resolution. In t
he case of CsI, the use of two illumination conditions, differing by a
factor 150 in intensity, showed the collapse of luminescence efficien
cy for very strong illumination. The quenching effect is discussed in
terms of the large increase of crystal excitation mean density, alteri
ng the usual process of luminescence centers production. (C) 1997 Amer
ican Institute of Physics.