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Benjamin Dietzek, Niklas hristensson, Torbjörn Pascher, Tõnu Pullerits, and Arkady Yartsev

Ultrafast Excited-State Isomerization Dynamics of 1,1‘-Diethyl-2,2‘-Cyanine Studied by Four-Wave Mixing Spectroscopy. Benjamin Dietzek, Niklas hristensson, Torbjörn Pascher, Tõnu Pullerits, and Arkady Yartsev J. Phys. Chem. B, 2007, 111 (19), pp 5396–5404. Miyasaka Lab. Masayasu Muramatsu.

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Benjamin Dietzek, Niklas hristensson, Torbjörn Pascher, Tõnu Pullerits, and Arkady Yartsev

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  1. Ultrafast Excited-State Isomerization Dynamics of 1,1‘-Diethyl-2,2‘-Cyanine Studied by Four-Wave Mixing Spectroscopy Benjamin Dietzek, Niklas hristensson, Torbjörn Pascher, Tõnu Pullerits, and Arkady Yartsev J. Phys. Chem. B, 2007, 111 (19), pp 5396–5404 Miyasaka Lab. Masayasu Muramatsu

  2. Contents • Introduction • Photoinduced Isomerization • 1122CExcited-State bond-twisting motion • Experimentalmethod • Transient Absorption • TransientGrating • Three-pulse photon echo peak-shift • Results ＆ Discussion • Summary

  3. trans-stilbene 11-cis retinal hn’ 254nm hn 313nm hn 200fs cis-stilbene all-trans retinal Photoinduced Isomerization Control pathway rate.etc eye sight model systemvs biological system →function of the protein matrix

  4. Excited-State bond-twisting motion Methanol 538nm 523nm 500ps trans-1122C cis-1122C

  5. Probe I DA = -log I0 DA A a b a b Transient Absorption Pump Transient species Sample hn a → b A Reference a b

  6. Pulse participation Excited State Absorption （ESA） Ground State Bleach （GSB） Stimulated Emission （SE） Hole spectrum time

  7. Transient Grating （TG） 2pulse interference １）　Thermal change ２）　Volume change ３）　Spectrum change 3pulse interference n(t)：refracture index k(t)：absorbance

  8. Three-pulse photon echo peak-shift τ≫0：decoherent→no echo T≫0：vanish diffraction fringe→no echo

  9. Three-pulse photon echo peak-shift Signal in k3+k2-k1 direction 100fs 1ps 10ps 100ps

  10. ESA:excited-state population 405nm(filled triangle) 573nm(open star) 700nm(open triangle) 850nm(open aquare) 1000nm(filled circle) 4.9ps 405nm Transient Absorption Stimulated emission

  11. Transient Grating 548nm Viscosity, large →Decay time, large Rise:Stimulated Emission (dark state) Decay:Internal Conversion

  12. Transient Grating 530nm 495nm 530nm 495nm 495nm：no emission →no rise

  13. 3PEPS 548nm viscosity large ↓ inhomogeneity large Rise:Stimulated Emission (another state) The osillation pattern is insensitive to solvent →It is not related to torsion

  14. 3PEPS methanol propanol Vibrational Relaxation 548nm(red), 530nm(green), 495nm(blue) 5ps~ Rise: cis isomer formation ? or Ultrafast Internal Conversion ?

  15. 1ps 4.9ps 538nm 523nm 500ps Summary • Transient Absorption • ESA(405nm): ~1ps(flat),τ=4.9ps(decay) • SE(548nm):~1ps(decay)→dark state • Transient Grating • wavelength dependent rise ← ESA • solvent dependent decay ← internal conversion • 3PEPS • high viscosity →high inhomogeneity • rise(495nm) →cis isomer?

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