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Fast and efficient VUV/UV emissions from (Ba,La)F2:Er crystals
Andrzej J. Wojtowicz, Sebastian Janus and Dawid Piatkowski
N. Copernicus University, Torun, Poland
ICL ’08 7-11 July 2008, Lyon, France
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OUTLINE
Short Introduction to Rare Earth ions in solid state materials
VUV/ UV luminescence and luminescence excitation spectroscopy of (Ba,La)F2:Er;
experimental results
Model; configuration coordinate diagram
Summary
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INTRODUCTION
RE ions: [Xe]4fn, [Xe]4fn-15d
Intraconfigurational transitions 4fn → 4fn (sharp lines, parity forbidden slow emissions)
Interconfigurational transitions 4fn → 4fn-15d broad bands, parity allowed,
spin allowed/forbidden, emission fast/slow
5d crystal field states (CF structure), 5d-4fn-1 coupling (imposed on CF structure),
f-d exchange splitting (LS and HS states)
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Er3+; what do we expect?
strong Coulomb interaction between 11 4f electrons
High energy 4f11 levels (theory: the highest at about 100,000 cm-1,
the highest experimentally verified at 63,100 cm-1)
5d levels
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SUMMARY OF EXPERIMENAL RESULTS
EMISSIONS observed at 10 K:
FAST d-f emissions under 157 nm excitation (LS, J = 8)
SLOW d-f emissions under 165 nm excitation (HS, J = 8)
SLOW f-f emissions under 148 nm excitation (LS, J = 7)
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MODELConfiguration Coordinate Diagram
Assumptions:
All states of the same electronic configuration have the same
equilibrium position
BUT
The equilibrium positions for states of the 4f11 and 4f105d configurations are different
The energies taken from experiment
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Summary
Relatively slow nonradiative relaxation in (La,Ba)F2:Er between the lowest LS and HS 4f105d levels
Fast and efficient 4f105d → 4f11 emissions from the (LS, J = 8) level bypassing (HS, J = 8) 4f105d level
2G7/2 emission under the (LS, J = 7) level excitation at 10 K;
indirect identification of the 2G7/2 level
2G7/2 - THE HIGHEST KNOWN EMITTING 4f11-level of Er3+ ion in solid state material (66 100 cm-1)
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ACKNOWLEDGMENTS
S. Janus (PhD student), coauthor: experiment, time profile fits
D. Piatkowski (PhD student), coauthor: calculations of (Er3+)4f11 energy levels
Prof. M.F. Reid (University of Canterbury,
Christchurch, New Zealand)is gratefully acknowledged for providing
f-shell empirical programs to calculate 4f11 levels
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ACKNOWLEDGMENTS
SAMPLES and EXPERIMENTS
(Ba,La)F2:Er crystals grown at Optovac, MA, USA,
donated by Prof. A. Lempicki of Boston University
VUV and UV emission/excitation spectra, and time
profiles measured in 2007 at Superlumi station of
I–beamline, DORIS III, Hasylab, Hamburg, Germany
Prof. G. Zimmerer and Dr G. Stryganyuk
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VISIT the poster of
S. Janus
Mo – P – 087
High energy 4f11 and 4f105d
energy levels of Er3+ in BaF2
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