Modeling of recombination kinetics of radical pairs in magnetic field. Comparison with experimental dependences on the frequency of encounters in biradicals |
| |
Authors: | V F Tarasova P P Levin |
| |
Institution: | (1) N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 4 ul. Kosygina, 119991 Moscow, Russian Federation;(2) N. M. Emanuel' Institute of Biochemical Physics, Russian Academy of Sciences, 4 ul. Kosygina, 119991 Moscow, Russian Federation |
| |
Abstract: | The recombination kinetics of spin-correlated radical pairs (RPs) with three nonequivalent magnetic nuclei were calculated
under conditions of enforced encounters between radicals at time-independent frequency ndif. The simplest two-position model of a RP was used, which includes two states (contact state and distance-separated state)
of the RP, differing in magnitude of isotropic spin-spin exchange interaction between radicals. The calculated kinetic curves
were treated in terms of a three-exponential model. The dependences of corresponding rate constants (k
rec) on ndif, external magnetic field strength (B
0), and intensity, A
eff, of isotropic hyperfine coupling (HFC) were obtained. The k
rec-vs.-ndif or k
rec-vs.-viscosity (ndif varies simultaneously with the inverse lifetime of the contact state) plots pass through maxima whose positions are shifted
from the ndif region near the A
eff value at B
0 = 0.5 G toward high ndif values with an increase in B
0. At ndif ≫ A
eff, the k
rec-vs.-B
0 plots pass through maxima in the region B
0 = A
eff. The calculated dependences are compared with experimental data on recombination of biradicals. The results of calculations
show that the experimentally observed maxima on the k
rec-vs.-B
0 or k
rec-vs.-ndif plots can be due to peculiar features of the spin dynamics induced by the hyperfine coupling rather than the exchange interaction
effects, as is commonly accepted.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1103–1110, May, 2005. |
| |
Keywords: | radical pair biradical magnetic effect hyperfine interaction recombination kinetics Liouville equation |
本文献已被 SpringerLink 等数据库收录! |
|