24 September 1999 Ž . Chemical Physics Letters 311 1999 167–172 www.elsevier.nlrlocatercplett f–d Luminescence of Pr 3q and Ce 3q in the chloro-elpasolite Cs NaYCl 2 6 Mathieu Laroche a , Marco Bettinelli b , Sylvain Girard a , Richard Moncorge a, ) ´ a CIRIL, Equipe MIL, UMR 6637 CNRS r CEA r ISMRA 6, BouleÕard Marechal Juin, 14050 Caen Cedex, France b Dipartimento Scientifico e Tecnologico, UniÕersita di Verona, Ca’Vignal, Strada Le Grazie, 37134 Verona, Italy ` Received 1 June 1999; in final form 12 July 1999 Abstract Ž . 3q 3q A detailed study of the ultraviolet UV luminescence properties of the Pr and Ce ions in the elpasolite crystal Cs NaYCl is reported. The absorption and fluorescence spectra associated with the lowest excited states of the 4f5d and 5d 2 6 electronic configurations of the Pr 3q and Ce 3q ions, respectively, were recorded both at room temperature and at 77 K. The UV excitation on the Pr 3q ions was provided indirectly via a two step absorption process using the 3 P level of the 4f 2 0 configuration as an intermediate state. Pr 3q to Ce 3q energy transfer was then clearly evidenced. q 1999 Elsevier Science B.V. All rights reserved. 1. Introduction In the last few years, it has been shown that the 4f ny1 5d ™4f n broadband interconfigurational tran- sitions of trivalent lanthanide rare-earth ions can be useful for new tunable all-solid-state lasers in the Ž . blue and ultraviolet UV spectral domains. For ex- 3q 3q w x ample, Ce :YLF and Ce :LaF 1,2 have initially 3 been lased, and more recently Ce 3q :LiCAF, 3q w x 3q w x Ce :LiSAF 3–5 and Ce :LiLuF 6,7 have been 4 demonstrated as reliable and efficient tunable UV coherent sources. However, these materials have to be pumped with UV pump sources, which can lead to color center formation and very detrimental opti- cal losses, and their laser emissions are at the mo- ) Corresponding author. Tel.: q33-231-452558; fax: q33-231- 452557; e-mail: moncorge@spalp255.ismra.fr ment limited to the near-UV between about 280 and w x 335 nm 8,9 . Thus, there is currently substantial effort being made to study and lase other rare-earth- doped crystals which can emit in complementary UV emission domains and which can be pumped differ- ently. From this point of view, the Pr 3q - and Pr 3q rCe 3q -doped elpasolites seem to be very attrac- tive. The Pr 3q -doped materials are in general inter- esting, even though none of them have lased so far w x 10 , because they can be pumped sequentially, using the 4f 2 energy levels as intermediate steps, with bluervisible pump photons. As in the case of the 5d band of Ce 3q , the splitting of the energy levels of the 4f5d electronic configuration of Pr 3q strongly depends on its crystalline environment. Pr 3q -doped Ž materials such as fluorides and chlorides other than . elpasolites because of a weak local crystal field, usually lead to absorption and emission bands at wavelengths shorter than about 300 nm. On the other 0009-2614r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0009-2614 99 00853-2