Laser-induced Dielectric Breakdown Research Articles

Decomposition of Benzene during Impacts in N2-dominated Atmospheres

Benzene is a simple neutral aromatic compound found in molecular clouds, comets, and planetary atmospheres. It has been confirmed on Jupiter, Saturn, Titan, and is expected on exoplanets. In this paper, the decomposition of benzene in a simulated asteroid or comet impact into an N2-dominated atmosphere was investigated. The impact plasma was simulated with laser-induced dielectric breakdown and the gas phase decomposition products were observed using high-resolution Fourier transform infrared spectroscopy. The gas phase decomposition products involve mainly HCN, C2H2, and smaller amounts of CH4 with yields of 3.1%–24.0%, 0–11.7%, and 0.5%–3.3%, respectively. Furthermore, in presence of water, benzene also produces CO and CO2 with yields of 2.4%–35.1% and 0.01%–4.8%, respectively. The oxidation state of the product mixture is proportional to the water content. Apart from that, a black-brownish solid phase is formed during the experiments, which makes up about 60% of the original carbon content. Our results therefore show that in anoxic N2-dominated planetary atmospheres, impacts might lead to the depletion of benzene and the formation of HCN, C2H2, and CH4 and, in the presence of water, to the formation of CO and CO2.

Spectroscopy of Laser-Induced Dielectric Breakdown Plasma in Mixtures of Air with Inert Gases Ar, He, Kr, and Xe.

The generation of ozone and nitrogen oxides by laser-induced dielectric breakdown (LIDB) in mixtures of air with noble gases Ar, He, Kr, and Xe is investigated using OES and IR spectroscopy, mass spectrometry, and absorption spectrophotometry. It is shown that the formation of NO and NO2 noticeably depends on the type of inert gas; the more complex electronic configuration and the lower ionization potential of the inert gas led to increased production of NO and NO2. The formation of ozone occurs mainly due to the photolytic reaction outside the gas discharge zone. Equilibrium thermodynamic analysis showed that the formation of NO in mixtures of air with inert gases does not depend on the choice of an inert gas, while the equilibrium concentration of the NO+ ion decreases with increasing complexity of the electronic configuration of an inert gas.

Structural dynamics of water in a supersonic shockwave

We explore the pressure evolution and structural dynamics of transient phase transitions in a microfluidic water jet after laser-induced dielectric breakdown. To this end, we use a combined approach of near-field holography with single femtosecond x-ray free-electron laser pulses and x-ray diffraction. During cavitation and jet breakup, we observe shock wave emission along the jet. The formation of the shockwave is accompanied by pronounced changes in the structure factor of water as an evidence by a shift in the water diffraction peak. This indicates a transition to a high density liquid structure induced by the transient pressure increase.

Nitrogen Oxide Production in Laser‐Induced Breakdown Simulating Impacts on the Hadean Atmosphere

AbstractThe high‐energy‐density synthesis of NxOy species is simulated in gas mixtures representing an O2‐free early‐Earth atmosphere by terawatt‐kilojoule‐class laser‐induced dielectric breakdown (LIDB). These experiments differ from previous LIDB experiments due to the 100 times greater energy delivered per pulse and sensitive analysis of products by high‐resolution infrared spectroscopy. The measured yields of NO, N2O, and NO2 are 0.08–8 × 1015, 5 × 1012, and 0.03–7 × 1014 molec J −1. The high N2O yield is above the upper‐limit constraint of previous tabletop LIDB experiments and the expected yield of a thermochemical freeze‐out at any temperature between 2000 and 5000 K, while the NO and NO2 yields are in broad agreement with freeze‐out models. Using a one dimensional chemical model of the Hadean atmosphere and a simple model of late bombardment, we compute the source flux of N2O assuming the same high production yield as measured experimentally and find the steady‐state partial pressure of N2O is insufficient to warm the climate.

Dynamical rate equation model for femtosecond laser-induced breakdown in dielectrics

Experimental and theoretical studies of laser-induced breakdown in dielectrics provide conflicting conclusions about the possibility to trigger ionization avalanche on the subpicosecond time scale and the relative importance of carrier-impact ionization over field ionization. On the one hand, current models based on a single ionization-rate equation do not account for the gradual heating of the charge carriers, which, for short laser pulses, might not be sufficient to start an avalanche. On the other hand, kinetic models based on microscopic collision probabilities have led to variable outcomes that do not necessarily match experimental observations as a whole. In this paper, we present a rate-equation model that accounts for the avalanche process phenomenologically by using an auxiliary differential equation to track the gradual heating of the charge carriers and define the collisional impact rate dynamically. The computational simplicity of this dynamical rate-equation model offers the flexibility to extract effective values from experimental data. This is demonstrated by matching the experimental scaling trends for the laser-induced damage threshold of several dielectric materials for pulse durations ranging from a few fs to a few ps. Through numerical analysis, we show that the proposed model gives results comparable to those obtained with multiple rate equations and identify potential advantages for the development of large-scale, three-dimensional electromagnetic methods for the modeling of laser-induced breakdown in transparent media.

Short-pulsed laser-induced breakdown in dielectrics with strong electron superheating: diffusion-controlled kinetics of impact ionization and recombination

In this work we model the diffusion-controlled kinetic mechanisms of (i) the strong electron superheating above the critical energy of impact ionization that develops within the generated skin depth when the neutral atoms deplete and (ii) recombination effects, which are involved in short-pulsed laser-induced breakdown and after-pulse relaxation in dielectrics. In the numerical simulations we use (iii) the two-temperature model modified for laser-matter interaction with dielectrics in combination with (iv) a computational approach developed for treating the auto-oscillatory dynamics of the electron energy and density induced by the onset of impact ionization during pulsed laser excitation and after-pulse relaxation.

Laser induced dielectric breakdown in reactive mixture SiF4 + H2

Important chemical process of reduction of SiF4 by hydrogen is realized in laser induced dielectric breakdown (LIDB) plasma in a gas mixture of SiF4 and H2. The process may be an alternative to a method of plasma enhanced chemical vapor deposition (PECVD) which is commonly used for production of pure and isotopically pure silicon films. The composition of laser induced plasma in gases SiF4, SiF4 + H2, SiF4 + H2 + Ar at atmospheric pressure is studied and compared to the composition of inductively coupled plasma (ICP) in the same gases but at reduced pressure of 3 Torr. The gaseous products of chemical reactions are inferred from optical emission spectroscopy (OES) and IR spectroscopy. The reaction products of silicon fluoride SiF and fluorosilanes SiHxFy (x, y = 1, 2, 3) in LIDB plasma are observed and confirmed by equilibrium chemistry calculations and simulations of plasma expansion dynamics using a fluid dynamic-chemical plasma model. It is further suggested that chemisorption of fluorinated species like SiFx (x = 1, 2) followed by the surface reaction with H-atoms lead to a formation of silicon-to‑silicon bonds on a substrate surface. A conclusion is drawn that energetic laser induced plasma can prove efficient for one-step PECVD by hydrogen reduction of SiF4.

Laser induced dielectric breakdown for synthesis of chlorofluorosilanes

Tetrafluorosilane (SF4) and tetrachlorosilane (SiCl4) plasmas have been widely used as a source of either F or Cl for etching silicon or as a source of silicon for deposition of Si-based materials. Using different combinations of F and Cl in molecules of chlorofluorosilane SiFxCly adds additional flexibility in realization of these processes. Direct synthesis of SiFxCl4-x (x = 1, 2, 3) from SiF4 and SiCl4 is thermodynamically forbidden under standard conditions. This restriction is removed in low-temperature plasmas studied in this work: a laser induced dielectric breakdown (LIDB) plasma and steady-state inductively-coupled plasma (ICP). The plasmas differ in many respects including energy content, temperature, and electron density that lead to different ionization/excitation states of plasma species, which are observed from plasma optical emission spectra. IR spectroscopy and mass-spectrometry confirm the formation of three chlorofluorosilanes, SiF3Cl, SiF2Cl2, and SiFCl3 that constitute ∼60 % in products of LIDB plasma and split 50/50 between SiF3Cl, SiFCl3 and SiF2Cl2. Experimental observations are verified by equilibrium static calculations via the minimization of Gibbs free energy and by dynamic calculations via the chemical-hydrodynamic plasma model of a spherically expanding plasma plume. The both types of calculations qualitatively agree with the results of spectroscopic analysis and reproduce dominant presence of SiF2Cl2 as the temperature of the gas approaches the room temperature.

A Global Scale Scenario for Prebiotic Chemistry: Silica-Based Self-Assembled Mineral Structures and Formamide.

The pathway from simple abiotically made organic compounds to the molecular bricks of life, as we know it, is unknown. The most efficient geological abiotic route to organic compounds results from the aqueous dissolution of olivine, a reaction known as serpentinization (Sleep, N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12818–12822). In addition to molecular hydrogen and a reducing environment, serpentinization reactions lead to high-pH alkaline brines that can become easily enriched in silica. Under these chemical conditions, the formation of self-assembled nanocrystalline mineral composites, namely silica/carbonate biomorphs and metal silicate hydrate (MSH) tubular membranes (silica gardens), is unavoidable (Kellermeier, M., et al. In Methods in Enzymology, Research Methods in Biomineralization Science (De Yoreo, J., Ed.) Vol. 532, pp 225–256, Academic Press, Burlington, MA). The osmotically driven membranous structures have remarkable catalytic properties that could be operating in the reducing organic-rich chemical pot in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic molecules under mineral-driven catalytic conditions (Saladino, R., et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249–1253), proton irradiation (Saladino, R., et al. (2015) Proc. Natl. Acad. Sci. USA, 112, 2746–2755), and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657–662). Here, we show that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic acids, amino acids, and nucleobases. Membranes formed by the reaction of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower reactivities. The collections of compounds forming inside and outside the tubular membrane are clearly specific, demonstrating that the mineral self-assembled membranes at the same time create space compartmentalization and selective catalysis of the synthesis of relevant compounds. Rather than requiring odd local conditions, the prebiotic organic chemistry scenario for the origin of life appears to be common at a universal scale and, most probably, earlier than ever thought for our planet.

Spectroscopic investigations of high-energy-density plasma transformations in a simulated early reducing atmosphere containing methane, nitrogen and water.

Large-scale plasma was created in gas mixtures containing methane using high-power laser-induced dielectric breakdown (LIDB). The composition of the mixtures corresponded to a cometary and/or meteoritic impact into the early atmosphere of either Titan or Earth. A multiple-centimeter-sized fireball was created by focusing a single 100 J, 450 ps near-infrared laser pulse into the center of a 15 L gas cell. The excited reaction intermediates formed during the various stages of the LIDB plasma chemical evolution were investigated using optical emission spectroscopy (OES) with temporal resolution. The chemical consequences of laser-produced plasma generation in a CH4-N2-H2O mixture were investigated using high resolution Fourier-transform infrared absorption spectroscopy (FTIR) and gas selected ion flow tube spectrometry (SIFT). Several simple inorganic and organic compounds were identified in the reaction mixture exposed to ten laser sparks. Deuterated water (D2O) in a gas mixture was used to separate several of the produced isotopomers of acetylene, which were then quantified using the FTIR technique.

Laser-Induced Plasma Micromachining Process: Principles and Performance

Laser-induced plasma micromachining (LIP-MM) is a novel multimaterial and tool-less micromachining process. It utilizes tightly focused ultrashort laser irradiation to generate plasma through laser-induced dielectric breakdown in a dielectric material. The plasma facilitates material removal through plasma–matter interaction spot through vaporization and ablation. The paper introduces the LIP-MM process, discusses the underlying principles behind plasma generation and machining, and proves its feasibility by describing the experimental conditions under which plasma generation and machining occur. Upon successful commercial realization of this novel process, the key benefits envisaged are micromachining with better accuracy and better surface integrity, minimal subsurface damage, relatively smaller heat-affected zone (HAZ) and low roughness in a wide range of materials including those that are difficult to machine by some of the most successful micromachining processes such as micro-electrodischarge machining (EDM) and laser ablation.

ChemInform Abstract: Laser‐Plasma Chemistry: Principles and Applications

AbstractReview: 37 refs.

On the Road from Formamide Ices to Nucleobases: IR-Spectroscopic Observation of a Direct Reaction between Cyano Radicals and Formamide in a High-Energy Impact Event

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.

Peculiarities of the electron avalanche for the case of relatively large photon energy

We applied a Monte Carlo simulation for studies of single-shot laser-induced breakdown in pure transparent dielectrics for the case when the photon energy is close to or exceeds mean electron energy. Avalanche ionization rate dependence on intensity was obtained by solving both the kinetic Fokker-Planck type equation and the quantum kinetic equation. Threshold scaling with pulse width was obtained in the range from 3 ps to 30 ns for several values of laser frequency and initial lattice temperature. Lattice heating influence (during the laser pulse action) on avalanche ionization rate was studied.

IR laser-induced decomposition in thiirane for gas-phase deposition of conjugated organosulfur polymer incorporating cycloheptasulfur

IR laser-induced dielectric breakdown in gaseous thiirane results in extrusion of sulfur, formation of volatile products (ethene, ethyne, and carbon disulfide) and deposition of a solid film of a conjugated sulfur-containing polymer incorporating cyclo-heptasulfur. The polymer structure was analyzed by FTIR and Raman spectroscopy and electron microscopy and found to consist of S–S bridges and conjugated C C units partly substituted with S atoms. The cyclo-heptasulfur (known as unstable at room temperature) survives in the polymer for months and is judged to be stabilized in inner layers of polymer phase. Heating of the polymer leads to evolution of a disordered graphitic carbon.

Pressure Dependence of Laser-Induced Dielectric Breakdown in Water

The effects of pressure on laser-induced breakdown events at superthreshold irradiances in water were investigated over a range of pressures from 0 to 1380 bar. Breakdown events were generated using 5-ns Nd:YAG laser pulses of wavelength 532-nm. Observations of breakdown events were made using imaging and single detector techniques. Applications for use as a static and/or acoustic pressure sensor were explored. Using imaging techniques over a range of static pressures from 0 to 275 bar, it was observed that the laser-induced breakdown threshold increased with increasing pressure. An ability to infer acoustic pressure via optical breakdown techniques using imaging was demonstrated. Single detector measurements over the same pressure range were observed to follow a similar trend.

Optodynamic observation of double laser-induced breakdown at the water surface

A measurement technique based on the combination of beam deflection probe and photographic detection of optical emission is introduced for the study of laser-induced dielectric breakdown in the vicinity of the air–water interface. The plasma was photographed with a CCD camera and the shock wave generated by the breakdown in the air and inside the water was detected with a beam deflection probe as a function of the focus position. The comparative analysis of the photographic images and the characteristics of the simultaneously recorded ultrasonic signals shows that the amplitudes and the arrival times of the ultrasonic waves can reliably describe the characteristics of the breakdown and its position relative to the water surface. At certain focus positions the existence of double breakdown is evident.

Investigation of laser–plasma chemistry in CO–N 2–H 2O mixtures using 18O labeled water

A large-scale plasma was created in CO–N 2–H 2O 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 CO 2. The competition of the CO + CO → CO 2 + C and CO + OH → CO 2 + H reactions in the CO 2 production was investigated using 18O labeled water. An analysis of the isotopomers was carried out by means of high-resolution FTIR spectroscopy.

Spectroscopic Investigations of High-Power Laser-Induced Dielectric Breakdown in Gas Mixtures Containing Carbon Monoxide

Large-scale plasma was created in gas mixtures containing carbon monoxide by high-power laser-induced dielectric breakdown (LIDB). 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 a single 85 J, 450 ps near-infrared laser pulse into the center of a 15 L gas cell. The excited reaction intermediates that formed in various stages of the LIDB plasma chemical evolution were investigated by optical emission spectroscopy (OES) with temporal resolution. Special attention was paid to any OES signs of molecular ions. However, carbon monoxide cations were registered only if their production was enhanced by Penning ionization, i.e., excess He was added to the CO. The chemical consequences of laser-produced plasma generation in a CO-N 2-H 2O mixture were investigated using high resolution Fourier-transform infrared absorption spectroscopy (FTIR) and gas chromatography (GC). Several simple inorganic and organic compounds were identified in the reaction mixture exposed to ten laser sparks. H 2 (18)O was used to avoid possible contamination. The large laser spark triggered more complex reactivity originating in carbon monoxide than expected, when taking into account the strong triple bond of carbon monoxide causing typically inefficient dissociation of this molecule in electrical discharges.

Optical emission studies of nitrogen plasma generated by IR CO2 laser pulses**In Memoriam: Professor Antonio Pardo Martinez.

Large-scale plasma produced in nitrogen gas at room temperature and pressures ranging from 4 × 103 to 1.2 × 105 Pa by high-power laser-induced dielectric breakdown (LIDB) has been investigated. Time-integrated optical nitrogen gas spectra excited from a CO2 laser have been measured and analysed. The spectrum of the generated plasma is dominated by the emission of strong N+ and N and very weak N2+ atomic lines and molecular features of N+2(B2Σ+u–X2Σ+g), N+2(D2Πg–A2Πu), N2(C3Πu–B3Πg) and very weak N2(B3Πg–A3Σ+u). The relative intensities of the 0–0 band heads in the N2(C–B) and N+2(B–X) systems are very weak as compared with the chemiluminescence spectrum of nitrogen formed in a glow discharge. An excitation temperature Texc = 21 000 ± 1300 K was calculated by means of the relative intensity of ionized nitrogen atomic lines assuming local thermodynamic equilibrium. Optical breakdown threshold intensities in N2 at 9.621 µm have been determined. The physical processes leading to the LIDB of nitrogen in the power density range 0.4 < J < 4.5 GW cm−2 have been analysed. From our experimental observations we can suggest that, although the first electrons must appear via multiphoton ionization or natural ionization, electron cascade is the main mechanism responsible for the LIDB in nitrogen.