PHOTOCHEMICAL CHARGE SEPARATION SUPPRESSED BY SPIN CONVERSION

We present the unified theory of binary tripler stare ionization follo wed by spin conversion to a singlet state of radical ion pair (RIP) an d subsequent spin-allowed recombination which hinders the charge separ ation. An analytical theory of RIPs recombination in contact approxima tion is developed. At slow diffusion the previous results which ignore d the spin states have been confirmed, though the effective recombinat ion constant is weighted with an equilibrium share of singlet state, 1 /4. At faster diffusion, the spin conversion becomes a limiting stage if not completed during encounter and/or delivery time (from the initi al distance to contact). The analytical and numerical study of charge separation in polar solutions shows that initial interion distance is an important factor in determining the quantum yield dependence on enc ounter diffusion and spin conversion rates. At distant starts the diff usional control of geminate recombination gives way to kinetic control and/or to spin conversion control as diffusion increases. At any diff usion the quantum yield of RIPs separation decreases with the magnetic field if the latter accelerates the spin conversion.