Delayed ejection of cluster ions from a liquid–water beam following Mid-IR and Near-IR laser irradiation

Ions, OH−(H2O)n, were produced from a liquid beam of pure water by irradiation of a Mid- and a Near-IR lasers resonant to the fundamental and the forth harmonic of the OH vibration of the liquid water, respectively. The ions were composed of two components originating from the liquid beam surface and the inside, which liberated the ions into the gas phase at 0.2 and 1.7 ± 0.2 μs, respectively, after the Near-IR excitation. The Near-IR excitation created an ion pair (H+⋯OH−) in the course of non-equilibrium disintegration of the liquid beam induced by the Mid-IR excitation.