Photoelectrons in Rb/THF Solution: Spectral Dependence of Photodetachment Cross-Section

Photoconductivity method, combined with laser pulse excitation, was employed to obtain the spectral dependence of electron photodetachment in rubidium-tetrahydrofuran (Rb/THF) solution at room temperature. Wavelength dependence of photodetachment cross section, σpd, qualitatively retraces that of the optical absorption cross section, σa. Moreover, a wavelength dependence of the quantum yield, κ = σpd/σa, was also found, where κ ≈ 0.03 is held constant for the wavelengths region λ ≥ 680 nm (hν ≤ 1.8 eV). Also, in the short wavelengths region, λ ≤ 510 nm (hν ≥ 2.4 eV), κ is constant, but almost three times larger (κ ≈ 0.085). The inflection region is located approximately at hν = 2.2 eV, that coincides with the energy of Rb- ground state relative to the lower edge of the conduction band of THF. Mechanism of Charge-Transfer-To-Solvent (CTTS) with a subsequent release of a solvated electron is suggested to be valid below the conduction band of Rb/THF. It implies that κ = ks/(ks + kc) ≈ 0.03, and consequently,...