Visible anti-Stokes emission of Gd3+ in Cs2NaGdCl6 crystal

Visible emission, assigned to the transitions between the upper excited lev els of Gd3+ in the Cs2NaGdCl6 crystal upon excimer laser excitation, was ob served. The emitting level is covered by the intense 4f(6)5d bands. The obs erved anti-Stokes transitions result from a two-photon absorption, the natu re of which is discussed. Two mechanisms may have contributed to the observ ed visible signal: excited state absorption and two-photon absorption where the intermediate state belongs to the 4f(7) configuration. (C) 1998 Elsevi er Science B.V. All rights reserved.