Heterogeneous clusters as a model system for the study of ionization dynamics within tampered samples

Abstract

Tampering of a sample with a layer of another material is a promising technique to slow down the expansion dynamics within laser irradiated samples, with sound implications for single-particle diffraction imaging. Ideally, if an imaged object is covered by a layer of another material, during the irradiation this layer will be primarily ionized and will expand fast due to Coulomb repulsion, whereas the object located within the net neutral core will expand more slowly (hydrodynamically). We investigate the details of the electronic damage within the tampered samples during their irradiation with an intense extreme ultraviolet (EUV) pulse. We study heterogeneous clusters composed of noble gas atoms, Xe and Ar, for which chemical-bond effects can be neglected. Using a fully nonequilibrium kinetic equation code, we demonstrate the influence of cluster composition on ionization dynamics; in particular, on the electronic damage. The results are obtained for the wavelength of 32 nm, which is available at the free-electron laser in Hamburg (FLASH) facility, but our conclusions can also have implications for samples with a more complex structure and irradiated at a much shorter wavelength.

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

“…This confirms the earlier finding that the presence of a heavier element covering a low-Z material can enhance the damage in the low-Z material. 71 Despite the fact that part of the energy deposited by radiation in tungsten is transferred by electrons to diamond, the radiation dose remaining in tungsten is still sufficiently high to evaporate the tungsten layer (these doses were estimated to be 2.4, 3.0, and 7.2 eV/atom for the three considered fluences), in agreement with the experimental observation.…”

“…Thus, a dedicated analysis of the damage threshold is necessary for any specific multilayer composition. 71 TABLE I. Comparison of photoabsorption in diamond with the energy deposition made by electrons from the 200-nm tungsten layer put on top of diamond.…”

Nanoplasma Dynamics of Single Large Xenon Clusters Irradiated with Superintense X-Ray Pulses from the Linac Coherent Light Source Free-Electron Laser

“…It is noted that this observation is quite surprising, as for the most highly charged clusters less than 1% of the photoactivated electrons can leave before the photoemission is frustrated in the increasing cluster Coulomb potential [13]. Our findings are also vastly different as compared to results of earlier experiments with about one order of magnitude lower photon energies where very efficient nanoplasma recombination mechanisms have been found [17,19]. The initial photoionization processes are similar for both cases, and they are guided by the atomic photoabsorption cross sections and subsequent inner-shell vacancy decay.…”

“…In dense nanoplasma, the cluster ionization can be further enhanced by energy-exchanging electron collisions [15]. For photon energies of % 100 eV, large clusters are transiently highly charged [16] before they disintegrate in a hydrodynamic expansion accompanied by recombination of the cluster core [17][18][19].…”

Charge and energy transfer in argon-core–neon-shell clusters irradiated by free-electron-laser pulses at 62 nm

“…Charge and energy transfer were estimated, and the results support the advantage of the core-shell structure for weakening the Coulomb explosion of laser-irradiated cluster cores. The current finding may be of great importance with respect to suggestions to delay and reduce the Coulomb explosion of biomolecules by embedding them in a tamper [35][36][37][38][39][40] for future x-ray-diffraction imaging experiments using x-ray lasers.…”