Communication: Mapping water collisions for interstellar space conditions

Abstract

We report a joint experimental and theoretical study that directly tests the quality of the potential energy surfaces used to calculate energy changing cross sections of water in collision with helium and molecular hydrogen, at conditions relevant for astrophysics. Fully state-to-state differential cross sections are measured for H2 O-He and H2O-H2 collisions at 429 and 575 cm-1 collision energy, respectively. We compare these differential cross sections with theoretical ones for H2 O+ H 2 derived from state-of-the-art potential energy surfaces [P. Valiron, J. Chem. Phys. 129, 134306 (2008)] and quantum scattering calculations. This detailed comparison forms a stringent test of the validity of astrophysics calculations for energy changing rates in water. The agreement between theory and experiment is striking for most of the state-to-state differential cross sections measured. © 2010 American Institute of Physics.