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(R 1 -R 2 ) homolytic cleavage 3( R 1 R 2 ) ISC 1( R 1 R 2 )

1. “Cage” Reactions Involving Radical Pairs. Model System. • •. • •. (R 1 -R 2 ) homolytic cleavage 3( R 1 R 2 ) ISC 1( R 1 R 2 ). recombinations disproportionations. 2. The States of a Spin Correlated Radical Pair. vector model of electron spin. • •. • •.

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(R 1 -R 2 ) homolytic cleavage 3( R 1 R 2 ) ISC 1( R 1 R 2 )

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  1. 1 “Cage” Reactions Involving Radical Pairs Model System • • • • (R1-R2) homolytic cleavage 3(R1R2) ISC1(R1R2) recombinations disproportionations

  2. 2 The States of a Spin Correlated Radical Pair vector model of electron spin • • • • 1(R1R2) 3(R1R2)

  3. 3 ISC in Triplet Radical Pairs

  4. 4 Spin Rephasing Mechanism for ISC spin clock (top-down view, projection in the xy-plane) J < a S T0

  5. 5 Timescales for ISC in Radical Pairs T0 S kTS ~ (3 X 106)(gH±Msa1 ) Spin-orbit coupling, g rate, kTS Typical organic radical, g ~ 0.000-0.001 Earth’s H ~ 1G 3 X 103 Hz Lab H ~ 100,000G 3 X 108 Hz Hyperfine coupling, a Typical organic radical, a~ 10-100G 3 X 107 - 3 X 108 Hz 2 mechanisms: Spin Rephasing (g) and Spin Flipping (a)

  6. 6 Ms = 0 Spin Rephasing a >>>H No nuclear spin flip involved Spin Flipping Ms = ± 1/2 , a1 is positive Sort magnetic nuclei from nonmagnetic nuclei! Power of Spin in Product Distribution T0 S kTS ~ (3 X 106)(gH±Msa1 ) then kTS+1/2 > kTS-1/2 Sort nuclear spin states! Polarized (non-Boltzmann) product distribution!

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