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trans → S χ → S 1 → trans -T 1 → 3 bir → ana

Picosecond pump-probe experiments. trans ana. Pump:270 nm. trans. ana. 15 ns. ⊿ A = A ana － A trans. ana － trans. Reaction is completed within 15 ns. trans → S χ → S 1 → trans -T 1 → 3 bir → ana. Picosecond pump-probe experiments. trans ana. Pump:2 ４８ nm.

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trans → S χ → S 1 → trans -T 1 → 3 bir → ana

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  1. Picosecond pump-probe experiments trans ana Pump:270 nm trans ana 15 ns ⊿A = Aana－ Atrans ana－trans Reaction is completed within 15 ns. trans → Sχ → S1 → trans-T1 → 3bir → ana

  2. Picosecond pump-probe experiments trans ana Pump:2４８ nm Not change any further ana → ana - S1 : Red(2ps) ana - S1 → ana - T1 Blue(40ps) : 2 ps trans 40 ps ana ana → S1 → ana-T1 → ・・・

  3. Re-excitation Nanosecond kinetic and spectrographic laser flash photolysis Probe:480 nm Pump:308 nm (the formation of ana-1) t / ms

  4. Re-excitation Nanosecond kinetic and spectrographic laser flash photolysis Re-excitation trans → Sχ → S1 → trans-T1 → 3bir → ana → ・・・ Femtosecond laser Nanosecond laser 15×10-5 ns 25 ns ~ 15 ns ~ 15 ns

  5. Nanosecond kinetic and spectrographic laser flash photolysis Probe 480 nm Pump:308 nm (the formation of ana-1) rise step t / ms

  6. (trans → ana) (ana → trans) － trans ana Nanosecond kinetic and spectrographic laser flash photolysis trans trans ana Step is no longer detectable. step The fast formation of ana-1

  7. trans ana Nanosecond kinetic and spectrographic laser flash photolysis Re-excitation Only rise is detected. rise The formation from ana-T1 ana→ ana-T1 → ana ana-T1 → ana ( trans → ana )

  8. Energy diagram for the photochromic transformation trans ana trans ana E Sχ S1 S1 T1 T1 bir 3bir ? trans ana trans ana Reaction coordinate

  9. Summary Four transient intermediates were detected by pump-probe spectroscopy of the trans-quinones 1. The associated processes are assigned to internal conversion Sχ → S1, intersystem crossing S1 → T1, and formation of a spiro-bridged triplet biradical intermediate that was directly observed for the first time. The reverse photoreaction, ana → trans, proceeds directly from the lowest singlet state.

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