Vibrational-state and isotope dependence of high-order harmonic generation in water molecules

Abstract

We report calculations on high-order harmonic generation in water molecules. Spectra are determined for various initial vibrational states of ${\mathrm{H}}_{2}\mathrm{O}$ and its isotope ${\mathrm{D}}_{2}\mathrm{O}$. It is demonstrated that the ratio of the spectra for ${\mathrm{D}}_{2}\mathrm{O}$ and ${\mathrm{H}}_{2}\mathrm{O}$ is close to unity when the initial state is the vibronic ground state, indicating that nuclear dynamics is of minor importance. For vibrationally excited initial states, the high-harmonic intensities show a clear dependence on both the initial-state quantum number and the isotopic species.