DYNAMICS OF SPIN-POLARIZED PHOTOELECTRONS IN RUBIDIUM-TETRAHYDROFURANSOLUTIONS

We present a Fourier transform EPR study of photoexcited rubidium-tetr ahydrofuran solutions (Rb/THF), in the absence and presence of the com plexing chelate 222 cryptand (Kp), Rb/THF/Kp. The temporal behavior of the EPR signals is interpreted in terms of two components participati ng in the complex processes, i.e., the spin-polarized photoelectrons a nd the solvated electrons that are coupled to the alkali-matal cations and, when present, to the cryptand molecules. The spin polarization m echanism is due to the radical pair mechanism, which is induced by cha rge transfer to solvent as a result of the photoabsorption. Spin relax ation times, measured directly in these systems, are discussed in term s of a site-exchange narrowing mechanism and a spin-rotation coupling mechanism in Rb/THF solutions and by collision-induced electron transf er in Rb/THF/Kp solutions.