Photodissociation of warm water: ab initio calculations of the room-temperature absorption spectrum

This Letter presents cross sections of water in the second absorption band obtained from quantum mechanical calculations. A Monte-Carlo sampling over the initial rotational state is applied in order to calculate the cross section for water at a temperature of 300 K (warm water). This makes a fair comparison with the experimental spectrum, only available for water at room temperature, possible. The overall rotation of the water molecule is treated exactly. The inclusion of initial rotational motion, which reduces the resonance structure in the spectrum, significantly improves the agreement between theory and experiment.