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Laser-assisted microanalysis offers the advantage of determining the spatially resolved compositions in 3D. Scanning a material with a sequence of sampling laser pulses and acquiring online the related spectra allow one to map the lateral and depth distribution of elements and molecules. However, the requirement to analyse smaller and smaller length-scales is challenged by focal diffraction as well as reduction of sensitivity at the nano-scale. Electron-based microprobes still offer unmatched spatial resolution. Disruptive improvements in laser technology are however demonstrated utilizing recently self-developed extreme ultraviolet or soft X-ray lasers. Firstly, a significant enhancement of the resolution is accomplished thanks to a much shorter wavelength, with respect to state-of-the-art commercial lasers. Furthermore, as the most innovative aspect, the sampling efficiency is enhanced using "ionizing radiation", i.e. directly activating the target material. The high photon-energy (20–100 eV) makes the sampling process essentially single-photon, whatever bond or ionization energy. Furthermore, the analytical setup is simplified to a sampling source and detector, i.e. without the need for a secondary ionization or excitation source as in some state-of-the-art analytical systems. In this review, fundamental aspects of X-ray laser desorption and ablation are discussed, and a survey of the available literature is presented. The main objective is to convince the reader that desorption or ablation in this spectral domain is a significantly cleaner sampling process, with large potential, still requiring investigation for a complete fundamental understanding. Applications of laser microanalysis are thus entering the nano-scale era, which shrinks the gap with electron-based microprobes. [ABSTRACT FROM AUTHOR]

In a mixture of molecular gases with compositions (CO2–N2–H2O and CO–N2–H2O) and total pressure close to that of the Earth’s early atmospheres, a centimeter-sized plasma was created by focusing a single 85-J, 450-ps near-infrared laser pulse in a center of 15-L gas cell. Chemical consequences of the laser-produced plasma generation in such a mixture were investigated using high-performance liquid chromatography with mass-spectrometric detection (HPLC/MS). Amino acids were identified in the reaction mixture containing CO2 as well as in that one based on CO, both exposed to 10 laser shots. [Copyright &y& Elsevier]

Ablation behavior of organic polymer (polymethylmethacrylate) and elemental solid (silicon) irradiated by single pulses of XUV radiation emitted from Z-pinch, plasma-focus, and laser-produced plasmas was investigated. The ablation characteristics measured for these plasma-based sources will be compared with those obtained for irradiation of samples with XUV radiation generated by a free-electron laser. [Copyright &y& Elsevier]

The application of fluorescent crystal media in wide-range X-ray detectors provides an opportunity to directly image the spatial distribution of ultraintense X-ray beams including investigation of the focal spot of free-electron lasers. Here the capabilities of the micro- and nano-focusing X-ray refractive optics available at the High Energy Density instrument of the European XFEL are reported, as measured in situ by means of a LiF fluorescent detector placed into and around the beam caustic. The intensity distribution of the beam focused down to several hundred nanometers was imaged at 9 keV photon energy. A deviation from the parabolic surface in a stack of nanofocusing Be compound refractive lenses (CRLs) was found to affect the resulting intensity distribution within the beam. Comparison of experimental patterns in the far field with patterns calculated for different CRL lens imperfections allowed the overall inhomogeneity in the CRL stack to be estimated. The precise determination of the focal spot size and shape on a sub-micrometer level is essential for a number of high energy density studies requiring either a pin-size backlighting spot or extreme intensities for X-ray heating. [ABSTRACT FROM AUTHOR]

We study the behavior of poly(methyl methacrylate) (PMMA) exposed to femtosecond pulses of extreme ultraviolet and X-ray laser radiation in the single-shot damage regime. The employed microscopic simulation traces induced electron cascades, the thermal energy exchange of electrons with atoms, nonthermal modification of the interatomic potential, and a triggered atomic response. We identify that the nonthermal hydrogen decoupling triggers ultrafast fragmentation of PMMA strains at the absorbed threshold dose of ~0.07 eV/atom. At higher doses, more hydrogen atoms detach from their parental molecules, which, at the dose of ~0.5 eV/atom, leads to a complete separation of hydrogens from carbon and oxygen atoms and fragmentation of MMA molecules. At the dose of ~0.7 eV/atom, the band gap completely collapses indicating that a metallic liquid is formed with complete atomic disorder. An estimated single-shot ablation threshold and a crater depth as functions of fluence agree well with the experimental data collected. [ABSTRACT FROM AUTHOR]

Abstract: A large-scale plasma was created in CO–N2–H2O gas mixtures by high-power laser-induced dielectric breakdown. The composition of the mixtures used corresponded to a cometary and/or meteoritic impact into the Earth’s early atmosphere. A multiple-centimeter-sized fireball was created by focusing near-infrared laser pulse into the centre of cell. The laser–plasma formation in the mixtures mainly leads to a production of CO2. The competition of the CO+CO→CO2 +C and CO+OH→CO2 +H reactions in the CO2 production was investigated using 18O labeled water. An analysis of the isotopomers was carried out by means of high-resolution FTIR spectroscopy. [Copyright &y& Elsevier]

Abstract: This article gives an account of chemical reactions initiated by laser-induced dielectric breakdown (LIDB) in homogeneous molecular gases. The systematic part of the article describes the laser-plasma-chemical behavior of simple inorganic gases and their mixtures, metal carbonyls and organometallics, and organic molecular gases. Research on LIDB-initiated chemical reactions producing well-defined fine solid particles has been triggered again recently by the advent of nanotechnologies. Laser ignition of fuel mixtures is also a well researched branch of laser-plasma chemistry because of strong commercial and military interests. However, the strongest current impulses for studying laser-spark chemistry come from planetary sciences, where laser sparks have been used as a laboratory model of high-energy-density phenomena (e.g., impact of extraterrestrial bodies, lightning) in planetary atmospheres. A single pulse from a high-power laser system was used to develop an improved method for investigating this phenomenon. The particular processes responsible for the chemical action of a laser spark are identified and described in detail by the end of the article. [Copyright &y& Elsevier]

Abstract: Double-walled carbon nanotubes were prepared by XeCl-laser irradiation of fullerene (C60 or C70) peapods. Raman spectroscopy evidences less defect structure of outer tubes, as compared to those in double-walled carbon nanotubes grown by thermal treatment of peapods. The diameter distribution also differs from that of the thermally prepared nanotubes. At the given laser fluence, the conversion of C70@SWCNT into double-walled carbon nanotubes was more efficient than the corresponding conversion of C60@SWCNT. [Copyright &y& Elsevier]

Fullerene oxides were the first observed fullerene derivatives and they have naturally attracted attention of both experiment and theory. C60O has represented a long standing case of experiment–theory disagreement, and there has been a similar problem with C60O2—both cases were explained by kinetic rather than thermodynamic control. In this contribution, we report the first computations of C84O. The computations are carried out with the PM3 quantum-chemical semiempirical method. Thermodynamic stabilities are evaluated for the electronic singlet and triplet states. The triplet states are computed at both restricted open-shell Hartree–Fock (ROHF) and unrestricted open-shell Hartree–Fock levels. The computations focus on the two most abundant C84 isomers—D2 and D2d, and especially deal with additions to their shortest and longest bonds. The D2/long structure is the lowest-energy species. The PM3/ROHF energy ordering of the C84O isomers in the first triplet electronic state is exactly the same as in the singlet electronic state and the relative energies are also quite similar. On the other hand, the kinetic stability order is just reversed compared to the thermodynamic order. Hence, for relatively short reaction times the C84O D2/short isomer should primarily be formed (in spite of the fact that it should be, thermodynamically, the least stable in the studied set). The computations point out various stability selection rules controlling production of fullerene-based materials. [Copyright &y& Elsevier]

We present a computational case study of X-ray single-particle imaging of hydrated proteins on an example of 2-Nitrogenase–Iron protein covered with water layers of various thickness, using a start-to-end simulation platform and experimental parameters of the SPB/SFX instrument at the European X-ray Free-Electron Laser facility. The simulations identify an optimal thickness of the water layer at which the effective resolution for imaging the hydrated sample becomes significantly higher than for the non-hydrated sample. This effect is lost when the water layer becomes too thick. Even though the detailed results presented pertain to the specific sample studied, the trends which we identify should also hold in a general case. We expect these findings will guide future single-particle imaging experiments using hydrated proteins. [ABSTRACT FROM AUTHOR]

Chemical environments of young planets are assumed to be significantly influenced by impacts of bodies lingering after the dissolution of the protoplanetary disk. We explore the chemical consequences of impacts of these bodies under reducing planetary atmospheres dominated by carbon monoxide, methane, and molecular nitrogen. Impacts were simulated by using a terawatt high-power laser system. Our experimental results show that one-pot impact-plasma-initiated synthesis of all the RNA canonical nucleobases and the simplest amino acid glycine is possible in this type of atmosphere in the presence of montmorillonite. This one-pot synthesis begins with de novo formation of hydrogen cyanide (HCN) and proceeds through intermediates such as cyanoacetylene and urea. [ABSTRACT FROM AUTHOR]

Extreme ultraviolet (XUV) capillary-discharge lasers (CDLs) are a suitable source for the efficient, clean ablation of ionic crystals, which are obviously difficult to ablate with conventional, long-wavelength lasers. In the present study, a single crystal of cesium iodide (CsI) was irradiated by multiple, focused 1.5-ns pulses of 46.9-nm radiation delivered from a compact XUV-CDL device operated at either 2-Hz or 3-Hz repetition rates. The ablation rates were determined from the depth of the craters produced by the accumulation of laser pulses. Langmuir probes were used to diagnose the plasma plume produced by the focused XUV-CDL beam. Both the electron density and electron temperature were sufficiently high to confirm that ablation was the key process in the observed CsI removal. Moreover, a CsI thin film on MgO substrate was prepared by XUV pulsed laser deposition; a fraction of the film was detected by X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Terrestrial volcanism has been one of the dominant geological forces shaping our planet since its earliest existence. Its associated phenomena, like atmospheric lightning and hydrothermal activity, provide a rich energy reservoir for chemical syntheses. Based on our laboratory simulations, we propose that on the early Earth volcanic activity inevitably led to a remarkable production of formic acid through various independent reaction channels. Large‐scale availability of atmospheric formic acid supports the idea of the high‐temperature accumulation of formamide in this primordial environment. [ABSTRACT FROM AUTHOR]

The durability of grazing- and normal-incidence optical coatings has been experimentally assessed under free-electron laser irradiation at various numbers of pulses up to 16 million shots and various fluence levels below 10% of the single-shot damage threshold. The experiment was performed at FLASH, the Free-electron LASer in Hamburg, using 13.5 nm extreme UV (EUV) radiation with 100 fs pulse duration. Polycrystalline ruthenium and amorphous carbon 50 nm thin films on silicon substrates were tested at total external reflection angles of 20° and 10° grazing incidence, respectively. Mo/Si periodical multilayer structures were tested in the Bragg reflection condition at 16° off-normal angle of incidence. The exposed areas were analysed post-mortem using differential contrast visible light microscopy, EUV reflectivity mapping and scanning X-ray photoelectron spectroscopy. The analysis revealed that Ru and Mo/Si coatings exposed to the highest dose and fluence level show a few per cent drop in their EUV reflectivity, which is explained by EUV-induced oxidation of the surface. [ABSTRACT FROM AUTHOR]

The problem of spontaneous magnetic field generation with nanosecond laser pulses raises a series of fundamental questions, including the intrinsic magnetization mechanisms in laser-driven plasmas and the understanding of charge-discharge processes in the irradiated target. These two issues are tightly bound as the charge-discharge processes are defined by the currents, which have in turn a feedback by magnetic fields in the plasma. Using direct polaro-interferometric measurements and theoretical analysis, we show that at parameters related to the PALS laser system (1.315 µm, 350 ps, and 1016 W/cm²), fast electrons play a decisive role in the generation of magnetic fields in the laser-driven plasma. Spatial distributions of electric currents were calculated from the measured magnetic field and plasma density distributions. The obtained results revealed the characteristics of strong currents observed in capacitor-coil magnetic generation schemes and open a new approach to fundamental studies related to magnetized plasmas. [ABSTRACT FROM AUTHOR]

The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoride targets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR) or extreme ultraviolet (XUV) lasers for the pulsed ablation and thin film deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoride targets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation) of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code) taking into account laser heating and surface evaporation of the lithium fluoride target occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave) model. [ABSTRACT FROM AUTHOR]

Application of a compact laser plasma source of soft X-rays in radiobiology studies is demonstrated. The source is based on a laser produced plasma as a result of irradiation of a double-stream gas puff target with nanosecond laser pulses from a commercially available Nd:YAG laser. The source allows irradiation of samples with soft X-ray pulses in the “water window” spectral range (wavelength: 2.3–4.4 nm; photon energy: 280–560 eV) in vacuum or a helium atmosphere at very high-dose rates and doses exceeding the kGy level. Single-strand breaks (SSB) and double-strand breaks (DBS) induced in DNA plasmids pBR322 and pUC19 have been measured. The different conformations of the plasmid DNA were separated by agarose gel electrophoresis. An exponential decrease in the supercoiled form with an increase in linear and relaxed forms of the plasmids has been observed as a function of increasing photon fluence. Significant difference between SSB and DSB in case of wet and dry samples was observed that is connected with the production of free radicals in the wet sample by soft X-ray photons and subsequent affecting the plasmid DNA. Therefore, the new source was validated to be useful for radiobiology experiments. [ABSTRACT FROM AUTHOR]

A desk-top laser-produced plasma (LPP) source of soft X-rays (SXR) has been developed for radiobiology research. The source is based on a double-stream gas puff target, irradiated with the focused beam of a commercial Nd:YAG laser. The source has been optimized to get a maximum photon emission from LPP in the X-ray “water window” spectral wavelength range from 2.3 nm (i.e., an absorption edge of oxygen) to 4.4 nm (i.e., an absorption edge of carbon) (280–540 eV in photon energy units) by using argon gas-puff target and spectral filtering by free-standing thin foils. The present source delivers nanosecond pulses of soft X-rays at a fluence of about 4.2 × 10 3 photons/μm 2 /pulse on a sample placed inside the vacuum chamber. In this paper, the source design, radiation output characterization measurements and initial irradiation experiments are described. The source can be useful in addressing observations related to biomolecular, cellular and organisms’ sensitivity to pulsed radiation in the “water window”, where carbon atoms absorb X-rays more strongly than the oxygen, mostly present in water. The combination of the SXR source and the radiobiology irradiation layout, reported in this article, make possible a systematic investigation of relationships between direct and indirect action of ionizing radiation, an increase of a local dose in carbon-rich compartments of the cell (e.g., lipid membranes), an experimental estimation of a particular role of the Auger effect (in particular in carbon atoms) in the damage to biological systems, and the study of ionization/excitation-density (LET – Linear Energy Transfer) and dose-rate effects in radiobiology. [ABSTRACT FROM AUTHOR]

Ionizing radiation induces a variety of DNA damages including single-strand breaks (SSBs), double-strand breaks (DSBs), abasic sites, modified sugars, and bases. Most theoretical and experimental studies have been focused on DNA strand scissions, in particular production of DNA double-strand breaks. DSBs have been proven to be a key damage at a molecular level responsible for the formation of chromosomal aberrations, leading often to cell death. We have studied the nature of DNA damage induced directly by the pulsed 46.9-nm (26.5 eV) radiation provided by an extreme ultraviolet (XUV) capillary-discharge Ne-like Ar laser (CDL). Doses up to 45 kGy were delivered with a repetition rate of 3 Hz. We studied the dependence of the yield of SSBs and DSBs of a simple model of DNA molecule (pBR322) on the CDL pulse fluence. Agarose gel electrophoresis method was used for determination of both SSB and DSB yields. The action cross sections of the single- and double-strand breaks of pBR322 plasmid DNA in solid state were determined. We observed an increase in the efficiency of strand-break induction in the supercoiled DNA as a function of laser pulse fluence. Results are compared to those acquired at synchrotron radiation facilities and other sources of extreme-ultraviolet and soft x-ray radiation. [ABSTRACT FROM AUTHOR]

The formamide-based synthesis of nucleic acids is considered as a nonaqueous scenario for the emergence of biomolecules from inorganic matter. In the current study, we scrutinized the chemical composition of formamide ices mixed with an FeNi meteorite material treated with laser-induced dielectric breakdown plasma created in nitrogen buffer gas. These experiments aimed to capture the first steps of those chemical transformations that may lead to the formation of nucleobases during the impact of an extraterrestrial icy body containing formamide on an early Earth atmosphere. High-resolution FT-IR spectroscopy combined with quantum chemical calculations was used to analyze the volatile fraction of the products formed during such an event. We have found that the spectrum of the evaporated formamide ices is dominated by the spectral signatures of the dimeric form of formamide. Upon exposure to laser sparks, new well-defined bands appear in the spectrum centered at ∼820, ∼ 995, and ∼ 1650 cm-1. On the basis of quantum chemical calculations, these bands can be assigned to the absorptions of 2-amino-2-hydroxy-acetonitrile and to 2-amino-2-hydroxy-malononitrile, which are formed in a direct reaction between formamide and CN• radicals upon the high-energy impact event. We also show that there is an exergonic reaction route via these intermediates leading to diaminomaleonitrile, which is generally considered to play a key role in the synthesis of nucleobases. [ABSTRACT FROM AUTHOR]

We present the x-ray optical design of the soft x-ray materials science instrument at the Linac Coherent Light Source, consisting of a varied line-spaced grating monochromator and Kirkpatrick-Baez refocusing optics. Results from the commissioning of the monochromator are shown. A resolving power of 3000 was achieved, which is within a factor of two of the design goal. [ABSTRACT FROM AUTHOR]

Conditions for ultrasound toluene extraction of synthetic C60 added to powdered bituminous coal were tested. High-performance liquid chromatography (HPLC) was used to determine the fullerene content in the obtained extracts. The results indicated a possible negative effect of sample demineralization (HCl/HF) and N2 purging on the extraction yield of C60. On the contrary, a 30% yield increase was registered when the coal was pre-extracted with pentane or pentane/toluene. The best conditions for C60 recovery in the investigated mixtures are 30 min of sonication at 280-285 K. The effects of sample filtration, sequential extraction, ultrasound bath power and treatments of C60 solution alone are also discussed. [ABSTRACT FROM AUTHOR]

The implosion of a solid deuterium gas-puff Z-pinch was studied on the S-300 pulsed power generator [A. S. Chernenko, et al., Proceedings of 11th Int. Conf. on High Power Particle Beams, 154 (1996)]. The peak neutron yield above 1010 was achieved on the current level of 2 MA. The fusion neutrons were generated at about 150 ns after the currant onset, i.e., during the stagnation and at the beginning of the expansion of a plasma column. The neutron emission lasted on average 25 ns. The neutron energy distribution function was reconstructed from 12 neutron time-of-flight signals by the Monte Carlo simulation. The side-on neutron energy spectra peaked at 2.42 ± 0.04 MeV with about 450-keV FWHM. In the downstream direction (i.e., the direction of the current flow from the anode toward the cathode), the peak neutron energy and the width of a neutron spectrum were 2.6 ± 0.1 MeV and 400 keV, respectively. The average kinetic energy of fast deuterons, which produced fusion neutrons, was about 100 keV. The generalized beam-target model probably fits best to the obtained experimental data. [ABSTRACT FROM AUTHOR]

Abstract: Soxhlet extraction, sonication, and ultracritical extraction were tested with respect to their capacity to extract fullerenes from natural carbonaceous materials. Toluene solutions with various contents of synthetic C60 were added to powdered graphite, shungite, bituminous coal, and quartz, with final C60 concentration 0.1–100ppm. The C60-doped materials were leached in three kinds of extraction apparatus. High-performance liquid chromatography (HPLC) was used to analyse the fullerene content in the obtained toluene extracts. Surprisingly low yields of the C60 extraction (most of them well below 5%) were determined for all the carbonaceous matrices and all the extraction techniques employed in the fullerene isolation. This finding has serious consequences for better understanding of the reported fullerene occurrence in the geological environment, because a greatly limited extraction yield can be responsible for some negative results of fullerene analyses in various geological samples. Both fullerene stability in solvents and fullerene interaction with the surfaces of geological carbonaceous matrices are discussed to explain the obtained results. [Copyright &y& Elsevier]

Abstract: Metal–fullerene (Ni–C60) thin film has been synthesized by co-deposition of Ni and C60 on the Ni/Si backing (i.e. on the Ni-coated Si wafer). The hybrid Ni+C60 mixture (with C60 affluent component) was grown as a nano-structured composite which consists of the dispersed Ni clusters and the complex C60/a-C-based matrix (a-C—amorphous carbon). The laser beam irradiation (Nd:YAG, λ=1064nm, τ=8ns) led to an unusual restructuring of the hybrid matter. In an area restricted by a small aperture, the single-pulse irradiation resulted in formation of a two-stage protrusion encircled with a-C ring and C60-depleted halo. On the other hand, a broad defocused beam irradiation resulted in extensive Ni/C60(a-C) phase separation with interspersed Ni- and C60(a-C)-rich zones. Surprisingly in the C60(a-C)-rich areas, a number of micrometer-sized periodic surface patterns (so-called LIPSS—laser-induced periodic surface structure) were observed. They consist of a massive central nucleus (made of a-C) surrounded with an array of periodic domains (made of C60(a-C)–Ni). We suggest that the formation of the LIPSS patterns of second kind is due to the coordinated relaxation of the stressed structure during the rapid dissipation of the laser beam energy. [Copyright &y& Elsevier]

Structural modifications of solid Si (0 0 1) targets exposed to the XUV TESLA free electron laser radiation were studied. The samples were irradiated with the photon energy centered at 14 eV, in short pulses of only 80 fs and of peak power up to 1 GW. The FEL beam was focused on sample surfaces to microspots of size 10–100 μm. The energy density in the spots varied from below the ablation threshold up to far above this threshold. The structural modifications induced with the irradiation were studied by AFM, Nomarski contrast microscopy and by X-ray diffraction methods. A variety of morphological structures created in the damaged areas was found. The maps of the X-ray diffracted intensity distribution recorded around chosen spots on the Si surface made it possible to probe the damage distribution range around the spots. The observed features are related to the FEL irradiation fluencies applied. [Copyright &y& Elsevier]