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Physics of Excited States in Solids ----- ultrafast laser studies and numerical modeling -----

Physics of Excited States in Solids ----- ultrafast laser studies and numerical modeling ----- Olin 209 ------- Qi Li – Ph.D. student Joel Grim – postdoc (WFU ‘12) Yan Wang – Shanghai visiting Keerthi Senevirathne - CEES Burak Ucer – Research Prof. Richard Williams – Prof.

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Physics of Excited States in Solids ----- ultrafast laser studies and numerical modeling -----

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  1. Physics of Excited States in Solids ----- ultrafast laser studies and numerical modeling ----- Olin 209 ------- Qi Li – Ph.D. student Joel Grim – postdoc (WFU ‘12) Yan Wang – Shanghai visiting KeerthiSenevirathne- CEES BurakUcer– Research Prof. Richard Williams – Prof.

  2. National Lab Partners Lawrence Berkeley National Laboratory Lawrence Livermore National Laboratory Pacific Northwest National Laboratory Oak Ridge National Laboratory National Nuclear Security Administration, Office of Defense Nuclear Nonproliferation, Office of Nonproliferation Research and Development (NA-22) of the U. S. Department of Energy under Contracts DE-NA0001012 & DE-AC02-05CH11231.

  3. . . . ~ 3 nm, ns duration, random location: – not by imaging!

  4. Particle track Laser experiment 1/e 6.1 eV laser 1/e 2Δr ~ µm - mm nm for α = 4 x 105 cm-1(NaI) equate e-h densities that produce the same quenching in both cases

  5. Measuring 2nd and 3rd order quenching: Z-scan nonlinear quenching set-up PMT uv laser translating lens integrating sphere

  6. excitation density (e-h/cm3) x 1020 0.07 0.3 5.8 0.3 0.07 0.03 K2 = 1 x 10-9 cm3s-1 Quenching is 2nd order in BGO. Excitons during NLQ.

  7. excitation density (e-h/cm3) x 1020 0.06 0.2 3.3 0.2 0.06 0.03 K3 = 8 x 10-31 cm6s-1 Quenching is pure 3rd order in SrI2. Free carriers during NLQ.

  8. Pacific Northwest National Lab Kinetic Monte Carlo August 2012 Wake Forest data

  9. We calculate “electron yield” Ye(Ei) to compare with SLYNCI and K-dip data, by the integral below. Feh(Ei,n0) is the fraction of all excitations produced at local density n0 by an electron of initial energy Ei including all delta rays (GEANT4). LLY(n0) is the local light yield model of nonlinear quenching and diffusion in Li et al JAP 2011).

  10. Cherepy et al Alekhin et al, SCINT LLY of Li et al JAP 2011 with K3 from z-scan k1 = 0.04 LY ≤ (1 - k1) = 0.96 80,000 ph/MeV

  11. Can we measure the radius of an electron track? . . . phone conversation with FeiGao (PNNL), Feb. 2012

  12. Track radius deduced from experiment NaI:Tl K-dip Khodyuk et al NaI:Tl z-scan 50% 0.4 mJ/cm2 4 x 105 cm-1 6.1 eV 1.6 x 1020 e-h/cm3

  13. Equating e-h densities, find radius z-scan K-dip (Vasil’ev, 2009) 3 nm in NaI near track end (PNNL, 2011) 2.6 nm Calculated immobile STH distribution = 2.8 nm [NWEGRIM, (PNNL) FeiGao 2012]

  14. CsI:Tl (0.3%) Induced Absorption

  15. Qi Li – Young Researcher Award – International Conference on Defects in Insulating Materials, Santa Fe, July 2012. First principles calculations and experiment predictions for iodine vacancy centers in SrI2

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