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Abstract

The combination of supersonic expansions with IR action spectroscopy techniques is the basis of many
successful approaches to study cluster structure and dynamics. The effects of temperature and
temperature evolution are important with regard to both the cluster synthesis and the cluster dynamics
upon IR excitation. In the past the combination of the sodium doping technique with IR excitation
enhanced near threshold photoionization has been successfully applied to study neutral, especially
water clusters. In this work we follow an overall examination approach for inspecting the interplay of
cluster temperature and cluster structure in the initial cooling process and in the IR excitation induced
heating of the clusters. In molecular simulations, we study the temperature dependent photoionization
spectra of the sodium doped clusters and the evaporative cooling process by water molecule ejection at
the cluster surface. We present a comprehensive analysis that provides constraints for the temperature
evolution from the nozzle to cluster detection in the mass spectrometer. We attribute the IR action
effect to the strong temperature dependence of sodium solvation in the IR excited clusters and we
discuss the effects of geometry changes during the IR multi-photon absorption process with regard to
application prospects of the method.