Ž . Chemical Physics 238 1998 429–435 The study on the magnetic field effect and the microwave effect on the photoconductivity observed in the photolysis of N, N, N X , N X -tetramethyl-p-phenylenediamine: theoretical calculation trial by the stochastic Liouville equation Yasutaka Kitahama a , Hisao Murai b, ) a Department of Chemistry, Graduate School of Science, Kyoto UniÕersity, Kyoto 606-8502, Japan b Department of Chemistry, Graduate School of Science, Tohoku UniÕersity, Sendai 980-8578, Japan Received 15 June 1998 Abstract The magnetic field effect on the photoconductivity and photoconductivity detected magnetic resonance spectra observed X X Ž . in the photoionization system of N, N, N , N -tetramethyl-p-phenylenediamine TMPD in alcohol are analyzed by the numerical calculation. The stochastic Liouville equation is applied to the study of the dynamics of the transiently formed Ž . radical–ion pair RIP . We succeeded in estimating the appropriate physical parameters according to the simulation of the line-width and the other observed phenomena. However, we realized that a new model, the formation of a cluster-like network structure between the RIP and the solvent molecules, should be introduced, because the calculation of the RIP dynamics in homogeneous solutions cannot reproduce the experimental results of the viscosity dependence. q 1998 Elsevier Science B.V. All rights reserved. 1. Introduction Ž . The behavior of a radical–ion pair RIP that is confined by the Coulomb force is different from that of a neutral radical pair. For example, the photoion- ization of N, N, N X , N X -tetramethyl-p-phenylenedia- Ž . mine TMPD in polar media, which forms the tran- Ž Øq . sient RIP of the TMPD cation radical TMPD Ž y . and the solvated electron e , is an interesting solv. system. This reaction has been investigated by a wx transient optical absorption method 1 , a transient w x photoconductivity method 1,2 , a time-resolved ESR ) Corresponding author. E-mail: murai@orgphys.chem.tohoku.ac.jp wx technique 3 , and a delayed fluorescence detected wx magnetic resonance method 4 . According to the reports of the transient optical absorption, the monophotonic ionization takes place through the in- termediate RIP formed from the excited singlet state of TMPD. The data of the external magnetic field Ž . effect MFE on the photoconductivity showed that the recombination mainly occurs through the triplet w x RIP 2,5,6 . Recently, a photoconductivity detected magnetic Ž . resonance PCDMR method was developed as a new ESR detection technique to study the RIP dy- w x namics 5,6 . PCDMR detects the escaped free ion radicals as the transient conductivity. In the system of TMPD in a mixed alcohol solution of 2-propanol 0301-0104r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0301-0104 98 00328-0