Rare-gas-cluster explosions under irradiation by intense short XUV pulses

Abstract

High-intensity, extreme-ultraviolet (XUV) femtosecond interactions with large rare-gas clusters of xenon and argon have been studied at a wavelength of 38 nm. Pulses of XUV radiation with nJ energy are produced by high-order harmonic conversion from a 35-fs, near-infrared, terawatt laser. Mass resolved ion spectra show charge states up to Xe 8+ and Ar 4+ . Kinetic-energy measurements of ions and electrons indicate that a nanoplasma is formed and a hydrodynamic cluster explosion ensues after heating by the short wavelength pulse. It appears that the observed charge states and electron temperatures are consistent with sequential, single-photon ionization and collisional ionization of ions that have had their ionization potential depressed by plasma continuum lowering in the cluster nanoplasma.

Induced transparency in the XUV: a pump-probe test of laser-cluster interactions

“…This would be unexpected since the effect was not detected in Nagler et al for a solid and the ionization potential lowering (IPL) mechanism's contribution decreases as the density of the cluster decreases. This decrease is due to the cluster's disintegration and the effect must tend to zero as the density becomes that of a gas since no such mechanism has been observed in gas [14,16,[36][37][38]. Lastly it is worth noting that our PIM used the most conservative assumptions and thus our results represent a lower bound on the experimental PIM results.…”

“…As the density of the cluster decreases with the cluster's disintegration, one would expect the IP lowering effect must also decrease. It would tend to zero as the density becomes that of a gas, since no IP lowering mechanism has been observed in gas [11,13,[24][25][26]. IP lowering effects would thus be sensitive to pump-probe delay time.…”

Explosion Dynamics of Methane Clusters Irradiated by 38 nm XUV Laser Pulses

“…After separation from the fundamental frequency, the filtered XUV pulse propagated into the interaction chamber, where it was focused by a f /12 Sc/Si multilayer, dielectric-coated, spherical mirror with a focal length of 12 cm. This mirror was designed to reflect only the 21 st harmonic (38 ± 5 nm), although aging resulted in some reflection of the neighboring harmonics (discussed in [9]). We reflected the incoming beam at about 5 o to normal incidence [16].…”

“…These two limits exhibit very different cluster explosion times and signatures. The ionization process leading to cluster explosion is strongly wavelength-dependent from IR through XUV [9,10] to the X-ray regime; because the kinetic energy of the released electrons determines the charge distribution within the cluster and therefore the explosion dynamics.…”

CO2exploding cluster dynamics probed by XUV fluorescence

“…However, impressive advances in laser science are quickly driving the investigation of laser-cluster interaction towards new frontiers. On the one hand, studies concerning clusters exposed to intense XUV and x-ray pulses are nowadays made possible by the availability of free electron lasers [14][15][16][17] and laser-driven high order harmonic sources [18,19]. On the other hand, the recent development of intense and ultrafast laser sources based on optical parametric amplifiers [20] has opened the way to the study of strong-field laser-matter interaction in the mid-IR spectral region [21].…”