EQUILIBRIUM STRUCTURE, FLUCTUATIONS, AND SPECTROSCOPY OF A SOLVATED ELECTRON IN METHANOL

Structural and spectroscopic properties of the equilibrium excess elec tron solvated in methanol are evaluated via adiabatic quantum molecula r dynamics simulations employing an electron-methanol pseudopotential based on that of Zhu and Cukier et al. [J. Chem. Phys. 98, 5679 (1993) ]. The solvated electron is localized in a roughly spherical ground el ectronic state of 2.5 Angstrom radius. The electron is surrounded by a pproximately six or seven methanol molecules in the first solvent shel l with mostly O-H bond orientation. Due to the strong electron-methano l coupling, solvent fluctuations result in substantial fluctuations of energy, size, and shape of the electron. The influences of radial flu ctuations and asymmetric distortions of solvent cavities are illustrat ed on both the solvation structure and the optical spectrum. The optic al-absorption spectrum of the solvated electron is dominated by transi tions to three clearly nondegenerate p-like excited states, The fluctu ations influence the s-p energy gap and modulate the p-p energy splitt ing leading to the calculated broad, featureless optical band. Compari son between systems containing flexible and rigid methanol molecules i s also reported. Unlike in water, characteristic fluctuations of appro ximately 20-ps time scale can occur in methanol. The structural and op tical consequences of these long timescale fluctuations are examined. (C) 1997 American Institute of Physics.