EFFECT OF PRESSURE ON THE FLUORESCENCE OF Pr3+ IN LaCl3

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EFFECT OF PRESSURE ON THE FLUORESCENCE OF Pr3+ IN LaCl3

T. Gregorian, W. Holzapfel

To cite this version:

T. Gregorian, W. Holzapfel. EFFECT OF PRESSURE ON THE FLUORESCENCE OF Pr3+ IN LaCl3. Journal de Physique Colloques, 1984, 45 (C8), pp.C8-41-C8-42. �10.1051/jphyscol:1984807�.

�jpa-00224305�

JOURNAL DE PHYSIQUE

Colloque C8, supplément au n ° l l , Tome 45, novembre 1984 page C8-41

EFFECT OF PRESSURE ON THE FLUORESCENCE OF P r

3 +

IN L a C l

3

T. Gregorian and W.B. Holzapfel

Faahbeveioh Physik, Universitat-GH-Paderborn, D-4790 Paderborn, F.P.G.

Résumé - l.s spectre de luminescence de Pr dans LaCl3 à température ambi- ante et à environ 120 K, Lie 0 à 12 GPa, est analysé. Une première analyse dos spectres indique que le déplacement des niveaux multiplets sous pres- sion est principalement dû aux variations de l'interaction électrostatique des électrons 4f et que la séparation de champ cristallin est deminée par une augmentation ce Agg et |Agnl.

Abst ract- The fluorescence spectrum of Pr in L a C l , at room temperature and about 120 K fron 0 to 12 GPa is analysed. A first analysis of the spectra indicates that the shift of the multiplet levels under pressure are mainly due to the changes in the electrostatic interaction of 4f electrons and the crystal field splittings are dominated by an increase of A

R R

and |A

60

|.

Introduction - The downward or red shift of the atomic energy levels during the complex formation (Nephelauxetic Effect) and the splitting into the crystal field levels are the two phenomena that interest us here. First attempts to study the effect of the pressure on absorption spectra of rare earth ions /'1/ indicated strong red shifts of

multiplet levels, but could not resolve changes in the crystal field splittings. Variations of the hf- levels under pressure have been studied previously on E u P

R

0 , , / 2 / , however, the low symmetry of this crystal did not allow for a quantitative evaluation of the oh served variation in the crystal field levels.

For a theoretical interpretation of these red shifts and changes in the crystal field s p l i t t i n g s , P r

3 +

is one of the most favourable candidates. It has relatively simple ground state configuration of two 4 f electrons and L a C l , is a host lattice with high point symmetry ( C -^, ) at the rare earth ' ion site.

1. E xperimental - The fluorescence of Pr was observed at room temperature and also at about 120 K, from P - ( 0 ) , P . ( 1 ) , P

n

and 1 "5 3

D_(0) levels to the various crystal field components of F , F , 3 3 3 3

F , H , H and H / 3 / w h e r e t h e numbers i n parenthesis i n d i c a t e the crystal quantum numbers. The pressure induced shift, of the 25 observed lines are given in Fig. 1.

The pressure was generated by a diamond anvil cell / 2 / . Fluorescence measurements up to 12 GPa en samples with or without pressure transmitting media indicated that the present results are nut strongly affected by non hydrostatic stresses.

2. Results - A first evaluation of the changes in these crystal field splittings indicates that the crystal field parameters / 4 / A

R R

and A

R

increase by about 3 0 % between D and 12 GPa and the ratio

A

R R

/ A = -".95(b) remains constant within the present accuracy. The

variation of A and A with pressure depends still strongly on

the approximations and "Ehc number of levels used in this preliminary

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984807

C8-42 JOURNAL

DE

PHYSIQUE

analysis. The e v a l u a t i o n o f t h e m u l t i p l e t c e n t e r s o f g r a v i t y show a n o v e r a l l d o w n w a r d s h i f t o f t h e s e l e v e l s . T h e s e s h i f t s a r e d o m i n a t e d b y t h e d e c r e a s e i n t h e S l a t e r p a r a m e t e r .

14700

1350

0 2 4 6 8 1 0 1 2 PRESSURE I GPa

F i g . l

-

E f f e c t of pressure on t h e 3+

.

fluorescence spectrum of P r I n LaC15

Acknowledgments. -We wish tocxpr.esc,our g r a t i t u d e t o Dr.T.Hangleiter and M r . 0.

Niggemeier f o r p r e p a r a t i o n o f the sample and t o 0r.R.Hirsch and Dr.P.Johannsen f o r h e l p f u l advices.

References

/I/ KEATING K.B. and DRICKAMER H.G., J.Chem.Phys. 45 (1961) 2729 /2/ t1UBER G.

,

SYASSEN K. and HOLZAPFEL W.B., ~ h ~ s x e v . ~ (1977)5123 /3/ DIEKE G.H. and SARUP R., J.Chem.Phys.g (1958)741

/4/ NEWMAN D. J., ~ d v . ~ h ~ s . ~ ( 1 9 7 1 )I 97