Spectroscopy of rare gas clusters using VUV light from a free-electron-laser

Abstract We performed time-of-flight (TOF) spectroscopy on a jet of rare gas clusters using light pulses at λ FEL  = 32 nm produced by the FLASH VUV freeelectron-laser (Hamburg, Germany) with a maximum peak power density of about 3 × 10 13  W/cm 2 at the sample. Energy deposition on the clusters was found to be strongly dependent on lambda and much more efficient in the VUV than in the IR and visible spectral range. We observed multiple ionization of rare gas atoms coming from clusters; the latter fragment completely upon absorption of a single pulse. We have also measured high quality photoelectron spectra. Small angle soft X-ray scattering (SAXS) from a single light pulse ( λ FEL  = 32 nm), was recorded with high signal to noise ratio for very large ( N atoms 3 × 10 6 ) Argon clusters.