GREEN EMISSION OF LACL3 - U3-PULSE( PRODUCED BY RED LASER)

A pulsed, red excitation of U3+-doped LaCl3 crystal at 16240 cm(-1) (I -4(9/2)-->K-2(13/2)) produces a green emission at 18180 cm(-1) (K-2(15 /2)-->I-4(9/2)). A similar effect of up-conversion has been found unde r an IR YAG:Nd excitation (I-4(9/2)-->H-2(9/2)). The induced emission was observed at low temperature (10 K). The intensity decay of the obs erved emission was analysed. After red excitation, the green emission is due to two processes: (a) a sequential absorption within one U3+ io n where the second photon populates the 5f(2)-6d bands and thus the en ergy is non-radiatively transferred to the K-2(15/2) emitting level an d (b) an energy transfer up-conversion process (ETU), which involves a U3+-U3+ pair. The up-conversion follows the scheme (F-4(9/2),F-4(9/2) )-->(H-2(9/2),H-2(11/2)')-35 cm(-1). The anti-Stokes emission produced by IR excitation is due to an excited state absorption process. (C) 1 998 Elsevier Science B.V. All rights reserved.