Infrared spectroscopy of size-selected water and methanol clusters

The field of weakly bound neutral molecular clusters has enjoyed a remarkable growth during the last years. The main experimental tools are combinations of different spectroscopic methods with size-selecting techniques. This article discusses results which are mainly based on the dispersion of the cluster sizes by the scattering from a helium beam combined with infrared photodissociation, resulting in depletion or enhancement of the beam, depending on the position of the detector. Size range from n=2 to 10 are covered. The tunable lasers employed include CO2 lasers in the 10 μm range or an optical parametric oscillator (OPO) system around 3 μm.