Collaborative Research: Multi-Photon Phosphors Based on Vacuum Ultraviolet Excitation R. S. Meltzer, University of Georgia (DMR-0305400)

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Collaborative Research Multi-Photon Phosphors
Based on Vacuum Ultraviolet Excitation R. S.
Meltzer, University of Georgia (DMR-0305400)

• Improvements of existing fluorescent lamps should
  include elimination of polluting mercury and an
  increase in the present 33 wall plug efficiency.
  Lamps can be designed with a xenon discharge
  replacing mercury but this will require a new
  generation of phosphors that produce two quanta
  (photons) of light for each deep ultraviolet
  photon absorbed from the xenon discharge. We are
  exploring the fundamental processes responsible
  for this quantum splitting. The figure to the
  right demonstrates that the initial quantum
  splitting step that excites two ions, both of
  which emit a photon, (population of the 6I
  state of Gd3 and 4F3/2 state of Nd3) occurs in
  sub microseconds, proving that short-range
  superexchange interactions between the Gd3-Nd3
  pair dominates. Studies in mixed crystals
  GdxY1-xLiF4Nd3 demonstrate the importance of
  energy migration among the Gd3 ions and explain
  why all known quantum splitting phosphors which
  depend on cross relaxation energy transfer
  require 100 occupation of one of the ions of the
  pair (here Gd3).

Figure Time evolution of the excited state
populations of Gd3 and Nd3 after pulsed
excitation of the 4f25d state of Nd3 at 157 nm
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Collaborative Research Multi-Photon Phosphors
Based on Vacuum Ultraviolet Excitation R. S.
Meltzer, University of Georgia (DMR-0305400)

• Two Ph.D. students and two visiting scholars,
  Professor Hyo Jin Seo (Pukyong National
  University, Korea) and Dr. Sergey Feofilov,
  (Ioffe Institute in St. Petersburg, Russia), are
  currently involved with this project. This
  research provides an opportunity for the students
  to gain expertise in phosphor development and to
  acquire the fundamental concepts in the optical
  properties of solids, especially those of rare
  earth doped insulators which form the basis for
  many phosphors. The training includes the gamut
  of techniques involved in vacuum ultraviolet
  (VUV) spectroscopy. Close cooperation in this
  project with scientists at Osram Sylvania allow
  students to understand the interfacing of
  research and development in an industrial
  setting. Collaborating with us is Professor
  Keszlers group at Oregon State University which
  designs and produces the phosphors used in this
  effort. Students at the two Universities see
  first hand the synergy necessary to develop new
  materials. Two students presented papers at the
  International Conference on Luminescence and the
  Conference on Dynamical Processes in Condensed
  Matter in China

Mr. Zhou, a Ph.D. graduate student, and Dr.
Feofilov, a visiting scientist, are shown
operating the VUV spectroscopy system.