Ultraviolet spectroscopy of water clusters: Excited electronic states and absorption line shapes of (H2O)n, n=2–6

Abstract

A semiempirical model is developed, based on ab initio calculations, to provide an analytic representation of excited-state potential energy surfaces for $({\mathrm{H}}_{\mathrm{2}}\mathrm{O}{)}_n,$ $\text{n=2–6.}$ Using quantum calculations of the ground vibrational states, the UV absorption spectra are computed by a semiclassical approximation, showing a strong blue-shift with extended blue tails relative to the monomer, but with an additional red tail in the case of the dimer absorption band. The nature of the excitonic states is discussed.