Rare Gas Clusters in Intense Laser Fields

Abstract

Recent experimental observations suggest that interaction of intense laser radiation with rare gas clusters jets provides an efficient source of X-rays and highly charged, energetic particles. Concerning the generation of X-rays the most prominent examples are the observation of: (i) Xe(M) an Kr(L) shell transitions with energies E up to 5keV reported by Rhodes and coworkers [1], (ii) non-coherent soft X-rays (E<500eV) on a nanosecond timescale reported by Perry and co-workers [2], and (iii) efficient high harmonic generation from Xenon clusters reported by Ditmire et al. [3], Regarding the production of energetic particles, Ditmire et al. [5] have reported Xeq+-ions with extremely high kinetic energies exceeding 100 keV when using 150fs pulses with intensities up to 1016W/cm2. Interestingly, Snyder et al. [4] were able to detect high charge states such as Xe20+ in a time-of-flight mass spectrometer after applying 350fs pulses at intensities of only 1015 W/cm2 to mixed He-Xe expansions. In a recent study of Argon clusters we have made very similar observations in a moderate intensity regime of 1014W/cm2 [6] using 30ps pulses at 1064nm. Our experimental results suggest that the underlying mechanism is efficient electron-ion collisional heating of cluster-sized nanoplasmas, similar to the interpretation proposed by Perry et al [2].