Picosecond dynamics of gas-phase dimers in liquid carbon dioxide

An inelastic neutron scattering and molecular dynamics simulation study of the interaction properties of liquid CO2 is reported. By means of an interaction-based interpretation of neutron scattering and simulation results for the dynamic structure factor we also show that ( CO 2 ) 2 equilibrium dimers characteristic of the gas phase are present in dense liquid carbon dioxide and predominantly contribute to the observed picosecond dynamics. Such a memory of the gas-phase structures was not observed in liquid methane. The role of anisotropy and strength of interactions on these important differences is discussed.