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RADIATIVE TRANSFER BETWEEN M AND M+
CENTERS IN NaF
L. Bosi
To cite this version:
C7-102 JOUKNÀE DE PHYSIQUE Colloque Cl, supplément au n° 12, Tome 37, Décembre 1976
RADIATIVE TRANSFER BETWEEN M AND M
+CENTERS IN N a F t
L. BGSI
Istituto di Fisica del Politecnico di Milano, and Gruppo Nazionale di Struttura della Materia, Milano, P. za Leonardo da Vinci, 32, Italy
Résumé. — On a mesuré la durée de vie radiative d'état excité IM+ pour la transition 1 sog -> 2 po-u
du centre M+ dans le NaF. On a trouvé que TM+ est presque indépendante de la température : TM+ = 33,4 ± 1,5 ns à la température de l'azote liquide. On a calculé les énergies d'absorption et la durée de vie radiative (29 ns) sur la base d'une ressemblance marquée entre un centre M+
et une molécule d'hydrogène ionisée. Lorsqu'on excite dans la bande M les échantillons qui contiennent les centres M+, on détecte une luminescence M+ typique. On peut interpréter le spectre
temporel de désexcitation observé, par le moyen de simples équations qui décrivent la cinétique d'excitation et d'émission comme une conséquence de transferts radiatifs entre centres M+ et M. Abstract. — The radiative lifetime TM+ of the ls<rB -* 2 p<7U transition of the M+ center in N a F
has been measured (TM+ = 33.4 ± 1.5 ns at LNT) and found nearly independent of the temperature up to RT. The absorption energies and the radiative lifetime (29 ns) have been calculated on the basis of a strict analogy between M+ centers and an ionized hydrogen-molecule. When samples
containing M+ centers are excited in the M band, a typical M+ luminescence can be detected : the decay spectrum observed can be interpreted in terms of simple equations describing the excita-tion and emission kinetics, as a consequence of a radiative transfer between M and M+ centers.
F. LtJTY. — You showed a diagram which indicates that excitation in the higher (7tu) states of the F ^
-center leads always to radiationless de-excitation into the <ru state. Is this well established, and does one
understand why this behaviour is different from the one observed in the F2 -center in KC1, where a second higher energy emission occurs under excitation into the 7ru state ?
L. Bosi. — The use of the continuum approxima-tion for M+-centers shows substantial agreement
t Bosi, L., Phys. Status Solidi (b) 75 (1976) K 27.
between theory and experiment. However, we may remark that the luminescence mechanisms for the M+-center in NaF are different from those observed
in KC1. In NaF, only one emission results and lumi-nescence corresponding to 2pnu -> lscg transition is
absent (COLLINS W. C. and SCHNEIDER, I., Phys.
Status Solidi (b) 51 (1972) 769). This fact has been
well established by these authors, but it is not clear the reason for the observed different behaviour of KC1 and NaF.
