Relaxation cell signaling system

Solutions were flowed through a suprasil flat cell (0.1 mm thickness) at rates between 0.1 - S.O mL/min in order to minimize any interference from signals produced by secondary photolysis of products. Time-resolved polarization evolution profiles for the formation and relaxation of the polarized radicals were measured at a constant magnetic field and monitored by both a Hitachi 40 MHz digital oscilloscope and a Stanford Research Systems gated integrator/boxcar averager at 5 ns resolution, and both coupled to a 486 PC desk-top microcomputer for analysis. 

The next two chapters are devoted to ultrafast radiationless transitions. In Chapter 5, the generalized linear response theory is used to treat the non-equilibrium dynamics of molecular systems. This method, based on the density matrix method, can also be used to calculate the transient spectroscopic signals that are often monitored experimentally. As an application of the method, the authors present the study of the interfadal photo-induced electron transfer in dye-sensitized solar cell as observed by transient absorption spectroscopy. Chapter 6 uses the density matrix method to discuss important processes that occur in the bacterial photosynthetic reaction center, which has congested electronic structure within 200-1500cm 1 and weak interactions between these electronic states. Therefore, this biological system is an ideal system to examine theoretical models (memory effect, coherence effect, vibrational relaxation, etc.) and techniques (generalized linear response theory, Forster-Dexter theory, Marcus theory, internal conversion theory, etc.) for treating ultrafast radiationless transition phenomena. 

Perkin Elmer MPF-3 spectrofluorometer. X- and Q-band measurements of EPR spectra were carried out at liquid nitrogen and liquid helium temperatures. Microcalorimetric measurements were performed on a LKB 10700 batch microcalorimeter. Temperature-jump relaxation kinetics were measured using a double beam instrument (18) with a cell adapted for anaerobic work. The relaxation signals were fed into an H.P. 2100 computer and analyzed as described in Ref. 7. The pulse radiolysis exepriments were carried out on the 5-MeV linear accelerator at the Hebrew University. Details of the system have been published previously (19). 

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