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FAST AND SLOW VUV/UV EMISSIONS FROM BaF 2 :Er AND (Ba,La)F 2 :Er

FAST AND SLOW VUV/UV EMISSIONS FROM BaF 2 :Er AND (Ba,La)F 2 :Er Andrzej J. Wojtowicz Uniwersytet M. Kopernika, Toruń, Poland ESTE 2010, WROCŁAW & Piechowice September 04-09, 2010. OUTLINE Samples and experiments

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FAST AND SLOW VUV/UV EMISSIONS FROM BaF 2 :Er AND (Ba,La)F 2 :Er

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  1. FAST AND SLOW VUV/UV EMISSIONS FROM BaF2:Er AND (Ba,La)F2:Er Andrzej J. WojtowiczUniwersytet M. Kopernika, Toruń, Poland ESTE 2010, WROCŁAW & PiechowiceSeptember 04-09, 2010

  2. OUTLINE Samples and experiments 4f n-15d – 4f nVUV luminescence spectra and time profiles of Er emission in BaF2:Er, (Ba,La)F2:Erwhat do we get; what did we expect Excitation spectra; energy levels MODEL; CONFIGURATION COORDINATE DIAGRAM BF and BLF sites in BaF2 and BaLaF2 SUMMARYand CONCLUSION

  3. SAMPLES and EXPERIMENTS (Ba,La)F2:Er (0.2%) La(20%), BaF2:Er (0.05%), BaF2:Er (0.075%) crystals grown at Optovac, MA, USA,donated by late Prof. A. Lempicki of Boston University VUV and UV emission/excitation spectra, and time profiles measured in 2007, 2008, 2009 and 2010 at Superlumi station of I–beamline, DORIS III, Hasylab, Hamburg, GermanyProf. G. Zimmerer (retired), Drs G. Stryganyuk, A. Kotlov

  4. VUV luminescence spectra and time profiles Similar spectra, very different time profiles

  5. Er3+; what did we expect? If relaxation between LS and HS d-levels were slower we could have a fast spin-allowed emissions from heavy rare earth ions But why does it work for LaBaF2 and not for BaF2?

  6. Excitation spectra of Er3+ emissions Fast emission bands (LS levels, spin-allowed transitions) Slow emission bands (HS levels, spin-forbidden transitions) Ground state is LS; 2S+1 = 4, emitting state may be LS or HS, 2S+1 = 6

  7. Emission and excitation spectra of BaLaF2:Er3+VUV emissions

  8. MODEL; CONFIGURATION COORDINATE DIAGRAM NOTE: Er in BLF should emit from 2G7/2 after excitation into 2nd LS band 4f n states parabolas intersecting 5d parabolas enable nonradiative energy relaxation process in BaF2 but not in (Ba,La)F2

  9. SLOW EMISSION FROM 2G7/2 of Er3+ in (Ba,La)F2 At 10 K excitation into second LS band generates emission from 2G7/2

  10. EXCITATION SPECTRA of BLF and BF sites in BaF2 BF site: 143, 153, 162 nm BLF site: 149, 159, 167 nm

  11. BLF and BF sites in BaF2 and BaLaF2 170 nm: spin-forbidden from BLF site, some overlap 547 nm: parity forbidden emission from 4S3/2 (Er green emission) BF site: 143, 153, 162 nm BLF site: 149, 159, 165 nm

  12. Emissions from BLF and BF sites in (Ba,La)F2:Er 153 nm excitation tuned to first LS state of BF site some excitation delivered to first LS state of BLF site 159 nm excitation tuned to first LS state of BLF site some excitation via relaxation delivered to HS state of BLF site 149 nm excitation tuned to second LS state of BLF site; relaxation to 2G7/2 some excitation via relaxation delivered to first LS and HS states of BLF site

  13. Emissions from BLF sites in BaF2:Er 159 nm excitation tuned to first LS state of BLF site

  14. Emissions from BF sites in BaF2:Er 159 nm excitation tuned to first LS state of BLF site

  15. SUMMARY and CONCLUSION FAST VUV EMISSION observed from Er in BLF sites in BaLaF:Er and BaF2:Er Only slow, spin-forbidden emission observed fromEr in BF sites in BaLaF2 and BaF2 BLF and BF sites abundant in BaF2 The number of BF sites is reduced in BaLaF2 To optimize material for FAST VUV EMISSIONmore studies of Er emission in mixed crystals are needed

  16. ACKNOWLEDGMENTS PhD students Experiment: S. Janus, P. Palczewski, M. Rozanski, M. Witkowski calculations of (Er3+)4f11 energy levels:D. Piatkowski 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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