Correlation of optical and electron spin resonance spectra for metal–electron species in alkali metal solutions

Pulse radiolysis of alkali metal cations (M+) in amines and tetrahydrofuran has demonstrated the formation of transient optical absorption bands attributed to a species of stoichiometry M. Such bands exhibit a distinct blue shift from that of es− observed in the same solvent. Comparisons with electron spin resonance (esr) spectra obtained in alkali metal solutions demonstrate that the blue shift can be correlated with the percent atomic character deduced for the species of the same stoichiometry. This correlation indicates that both the optical and esr spectra arise from the same species which, with decreasing solvent polarity, exhibits a continuous transition from well solvated ion-pairs to something approaching solvated atoms or tight ion-pairs.