Laser Microprobe Research Articles

High-speed PGC demodulation model and method with subnanometer displacement resolution in a fiber-optic micro-probe laser interferometer

As the key of embedded displacement measurement, a fiber-optic micro-probe laser interferometer (FMI) is of great interest in developing high-end equipment as well as precision metrology. However, conventional phase-generated carrier (PGC) approaches are for low-speed scenes and local error analysis, usually neglecting the global precision analysis and dynamic effect of system parameters under high-speed measurement, thus hindering their broad applications. We present a high-speed PGC demodulation model and method to achieve subnanometer displacement measurement precision in FMI. This model includes a global equivalent resolution analysis and revelation of the demodulation error mechanism. Utilizing this model, the failure issues regarding the PGC demodulation method under high speed and large range are addressed. Furthermore, an ultra-precision PGC demodulation algorithm based on the combination of static and dynamic delay adaptive regulation is proposed to enable high-speed and large-range displacement measurement. In this paper, the proposed model and algorithm are validated through simulation and experimental tests. The results demonstrate a displacement resolution of 0.1 nm with a standard deviation of less than 0.5 nm when measuring at a high velocity of 1.5 m/s—nearly a tenfold increase of the latest study.

Advancing (U-Th)/He Zircon Dating: Novel Approaches in Sample Preparation and Uncertainty Reduction

Abstract The laser microprobe (U-Th)/He dating method is a new and efficient technique that utilizes an interoperable and integrated suite of instruments, including the excimer laser system, quadrupole helium mass spectrometer, and quadrupole inductively coupled plasma mass spectrometer. To demonstrate the applicability of this new method, we applied both the conventional and laser microprobe techniques to the Sri Lanka zircon (LGC-1). We obtained twenty-two (U-Th)/He ages on nine shards using the laser microprobe method, showing an average (U-Th)/He age of 471.1 ± 16.6 Ma (1σ). This result is generally consistent with the mean conventional age (484.1 ± 9.6 Ma) for twenty-two zircon fragments. Both are nearly equal to the age value (~476 Ma) predicted by the He diffusion model and the thermal history model of Sri Lanka highland. The variations in the laser microprobe-derived ages are most likely caused by the uncertainties in volume measurements, which is also common in other studies. We used the Mahalanobis distance technique to reduce the volume measurement bias by identifying and eliminating abnormal data.

Technical note: In situ U–Th–He dating by 4He ∕ 3He laser microprobe analysis

Abstract. In situ U–Th–He geochronology is a potentially disruptive technique that combines laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with laser microprobe noble gas mass spectrometry. Despite its potential to revolutionize (detrital) thermochronology, in situ U–Th–He dating is not widely used due to persistent analytical challenges. A major issue is that current in situ U–Th–He dating approaches require that the U, Th, and He measurements are expressed in units of molar concentration, in contrast with conventional methods, which use units of molar abundance. Whereas molar abundances can be reliably determined by isotope dilution, accurate concentration measurements are not so easy to obtain. In the absence of matrix-matched U–Th concentration standards and accurate He ablation pit measurements, the required molar concentration calculations introduce an uncertainty that is higher than the conventional method, an uncertainty that is itself difficult to accurately quantify. We present a solution to this problem by using proton-induced 3He as a proxy for ablation pit volume and by pairing samples with a standard of known U–Th–He age. Thus, the U–Th–He age equation can be solved using relative rather than absolute concentration measurements. Pilot experiments show that the new method produces accurate results. However, it is prone to overdispersion, which is attributed to gradients in the proton fluence. These gradients can be measured, and their effect can be removed by fixing the geometry of the sample and the standard during the proton irradiation.

Evidence against a Late Heavy Bombardment event on Vesta

Impact events on planetary surfaces can leave significant volumes of melt, archived in planetary regoliths, which provide important information regarding the timing and nature of these events. For example, an observed ca. 3.9-4.1 Ga age cluster within lunar samples has been interpreted as indicative of a significant Solar System-wide event: the so-called “Late Heavy Bombardment”. Here, we report data from a laser ablation microprobe 40Ar/39Ar study of clasts within two unpaired howardite meteorites (NWA 1929 and Dho 485) to explore the impact history of their asteroid parent body – (4)Vesta. Laser microprobe dates for the howardites varied broadly between 3.5 to 4.5 Ga (NWA 1929) and 2.5 to 4.5 Ga (Dho 485), but show no clear cluster in ages at ca. 3.9-4.1 Ga. Consistent with previously reported U-Pb dates for HED meteorites, our data suggest an extended impact bombardment period on (4)Vesta as compared to the distribution of 40Ar/39Ar impactite dates for available samples from the Apollo and Luna sample archives. The impact history of Vesta revealed here highlights that current models of the impact flux in the inner Solar System based on the Late Heavy Bombardment hypothesis require refinement.

Mass Spectrometry-Based Differentiation of Oral Tongue Squamous Cell Carcinoma and Nontumor Regions With the SpiderMass Technology.

Oral cavity cancers are the 15th most common cancer with more than 350,000 new cases and ~178,000 deaths each year. Among them, squamous cell carcinoma (SCC) accounts for more than 90% of tumors located in the oral cavity and on oropharynx. For the oral cavity SCC, the surgical resection remains the primary course of treatment. Generally, surgical margins are defined intraoperatively using visual and tactile elements. However, in 15–30% of cases, positive margins are found after histopathological examination several days postsurgery. Technologies based on mass spectrometry (MS) were recently developed to help guide surgical resection. The SpiderMass technology is designed for in-vivo real-time analysis under minimally invasive conditions. This instrument achieves tissue microsampling and real-time molecular analysis with the combination of a laser microprobe and a mass spectrometer. It ultimately acts as a tool to support histopathological decision-making and diagnosis. This pilot study included 14 patients treated for tongue SCC (T1 to T4) with the surgical resection as the first line of treatment. Samples were first analyzed by a pathologist to macroscopically delineate the tumor, dysplasia, and peritumoral areas. The retrospective and prospective samples were sectioned into three consecutive sections and thaw-mounted on slides for H&E staining (7 μm), SpiderMass analysis (20 μm), and matrix-assisted laser desorption ionization (MALDI) MS imaging (12 μm). The SpiderMass microprobe collected lipidometabolic profiles of the dysplasia, tumor, and peritumoral regions annotated by the pathologist. The MS spectra were then subjected to the multivariate statistical analysis. The preliminary data demonstrate that the lipidometabolic molecular profiles collected with the SpiderMass are significantly different between the tumor and peritumoral regions enabling molecular classification to be established by linear discriminant analysis (LDA). MALDI images of the different samples were submitted to segmentation for cross instrument validation and revealed additional molecular discrimination within the tumor and nontumor regions. These very promising preliminary results show the applicability of the SpiderMass to SCC of the tongue and demonstrate its interest in the surgical treatment of head and neck cancers.

Technique for measuring the residual strain in strained Si/SiGe MOSFET structures using Raman spectroscopy

Abstract A measurement technique for studying the strain in Si/SiGe layers has been developed based on Raman spectroscopy using a laser microprobe. The Si/SiGe layers were grown by ultra-low pressure chemical vapour deposition in a modified molecular beam epitaxy system. The structures consisted of a strained Si grown on relaxed Si1– x Ge x (x = 0.1, 0.15 . . . 0.35), where the Si channel thickness was varied between 5 and 10 nm. Raman spectroscopy using a 514 nm laser indicated a significant shift in the Si peak from the SiGe layer; the position of this peak is related to the strain in the layer and strongly depends on Ge content, decreasing with increasing Ge in the virtual substrate. However, the strained Si peak shows a considerable overlap with the Si in SiGe peak and is difficult to deconvolute by conventional peak fitting approaches. The residual strain in the thin heterostructure Si/SiGe layers was, therefore, investigated before and after selectively etching the Si. The strain in the channel increased with Ge content in the underlying SiGe as expected, confirming that the high-temperature device processing did not degrade the channel macrostrain.

Laser microprobe noble gases and nitrogen analysis of chondrules from the Dhajala chondrite

AbstractNoble gases and nitrogen are investigated in eight individual chondrules of the Dhajala H3.8 chondrite. The mean cosmic ray exposure age of the chondrules using 21Ne and 38Ar is 5.9 ± 3.0 Ma. There is no significant evidence of a pre‐exposure for these chondrules. All the measured chondrules contain variable amounts of radiogenic 129Xe. Noble gas analysis indicates Q‐type gas incorporated in the chondrules. The chondrules have variable amounts of N2. The chondrules have distinct trapped N isotopic composition (δ15Nt varies from −24.1 ± 8.4‰ to 89.1 ± 12.7‰), which is inconsistent with Q‐gas and solar wind. These inconsistencies can be considered preliminary evidence in support of multiple trapped components in the chondrules. A heavy N signature component is observed in the chondrules studied contrasted with the solar wind composition. There is no correlation between the concentration of N2 and noble gases. Derivations of variable nitrogen observed in Dhajala (H3.8) chondrules reflect the gas captured at the time of formation, having heterogeneous isotopic signature in the nebula.

RESEARCH OF CORROSIVE DAMAGE TO THE PURPOSE OF FOOD PRODUCTION

Chemical and food processing environments contain chemically active ingredients such as oxygen, carbon dioxide (СО2), carbon monoxide (CO), sulfur, hydrogen, carbon acid ion and sulfuric acid ion, chlorine ions, impurities of calcium carbonate, iron, and hydrochloric acid, etc. All these factors lead to intensive corrosion of the equipment, reducing its reliability and durability. The corrosion-mechanical resistance of metal equipment, such as chemical and sugar plants, is of great importance for environmental and sanitary requirements that make it impossible to contaminate the product with metal ions. First of all, the tubes of evaporation stations, diffusion apparatuses and steam boilers of chemical and agro-processing (sugar) enterprises are exposed to corrosive damage caused by the negative influence of high-temperature and corrosive-active steam under high pressure. Significantly worsens this negative situation and deposition of sediments of salts, carbonates, acids, and others. The analysis of corrosives damages suggests that predominantly point and pitting corrosion predominate, which are exacerbated by internal or external loads. Unlike uniform corrosion, finding and slowing down which is not a particular difficulty, these types of corrosion are usually detected only after they are caused by emergency failures or fractures. Therefore, the main reasons for failures of technical facilities, among which the important placeis the destruction or operation of corrosion and corrosion and mechanical damage, must be carefully investigated and, if possible, eliminated on time. The complex of investigations of the damaged metal of evaporator tubes (steel 20 and 06X1) with a life time (from 0 to 20 years) included, along with standard, also special types of research, in particular: various variants of X-ray spectral analysis using a raster electron microscope "JSM-35CF" (Jeol, Japan),"SEM-515" with Philips microinalyzer "Link" scanning Auger electron spectroscopy (micro-analyzer "AES-2000"). In addition, the content and character of the distribution in the metal of pipes of water heaters of hydrogen, sulfur and oxygen were determined by the method of local mass spectral analysis with a laser microprobe, as well as by the method of melting of metal samples in the flow of carrier gas using the installation of the firm "Leco". With the help of high-precision metallographic experimental equipment, the mechanism of corrosion damage to the surfaces of evaporator tubes and the proposed measures for further research on methods for reducing the corrosion activity of the process environment and the adhesion of salt and carbonate sediments to the surface of the tubes of steam generators of food production is investigated. In particular, it has been shown that in order to eliminate metal corrosion and deposits of salt sediments in the form of scale on the surface of pipes of water heaters, it is necessary simultaneously to reduce the chemical activity of the water-vapor environment using different reagents, and to cover the tube with anticorrosive protective.

Construction materials wastes use to neutralize hazardous municipal water treatment sludge

The main objectives of this study were: 1. to control the efficiency of the application of marble polishing sludge as the main component (35–50 wt%) to neutralize hazardous municipal water treatment sludge (25–50 wt%) for the production of environmentally clean materials that match the mechanical properties required by the standard; lime production waste (10–30%) was used as bonding material; 2. to study the processes of the raw materials chemical interaction and new materials structure formation. The axial strength values of the developed material diverged among 4.02 MPa on the 3rd day, 5.98 MPa on the 28th day and 16.48 MPa on the 365th day. It was determined by the complementary X-ray fluorescence (XRF), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Laser Microprobe Mass Analyzer (LAMMA) and Atomic absorption spectroscopy (AAS) methods that the high strength of the materials from just industrial wastes was explained by the chemical interaction of the components in a highly alkaline aqueous medium with the synthesis of mainly amorphous sol-gel new formations. The results of leaching and solubility tests exhibited a very low level of no bonded metals compared to the current Brazilian sanitarian standards. This provides a potential to significantly reduce the environmental impact by recycling such industrial wastes. In addition, fewer waste dumps reduce the irreversible destruction of natural links by the quarrying of traditional natural building materials.

Microchemical and molecular dating.

The depth and reliability of archaeological and environmental information on ages, sources and pathways of carbon are being greatly enhanced through a new synergism between advances in “micro 14C dating” and advances in micro-organic analytical chemistry and individual particle characterization. Recent activities at the National Institute of Standards and Technology (NIST, formerly NBS) involving this linkage include dating individual amino acids isolated from bone collagen and the apportionment or tracing of individual carbon compounds derived from anthropogenic sources. Important knowledge has been gained through “direct” (sequential) and “indirect” (parallel) links between microchemistry and 14C measurement. The former is illustrated by 14C measurements on specific amino acids and on the polycyclic aromatic hydrocarbon (PAH) class of compounds. Isolation of the respective molecular fractions from far greater quantities of extraneous carbon held the key to valid dating and source apportionment respectively. Parallel data on 14C and molecular patterns promises new knowledge about the identity of sources of environmental carbon at the nanogram level through multivariate techniques such as principal component analysis and multiple linear regression. Examples are given for atmospheric particulate carbon, using PAH molecular patterns and laser microprobe mass spectral patterns.

Real-Time Molecular Diagnosis of Tumors Using Water-Assisted Laser Desorption/Ionization Mass Spectrometry Technology

Histopathological diagnosis of biopsy samples and margin assessment of surgical specimens are challenging aspects in sarcoma. Using dog patient tissues, we assessed the performance of a recently developed technology for fast exvivo molecular lipid-based diagnosis of sarcomas. The instrument is based on mass spectrometry (MS) molecular analysis through a laser microprobe operating under ambient conditions using excitation of endogenous water molecules. Classification models based on cancer/normal/necrotic, tumor grade, and subtypes showed a minimum of 97.63% correct classification. Specific markers of normal, cancer, and necrotic regions were identified by tandem MS and validated by MS imaging. Real-time detection capabilities were demonstrated by exvivo analysis with direct interrogation of classification models.

Микротопохимия конкреций пирита в кремнистых алевропелитах Юбилейного медноколчеданного месторождения (Южный Урал) по данным LA-IСP-MS

Object . The zonal pyrite nodules and metacrystals from siliceous siltstones of ore-bearing horizon of the Second ore body from the Yubileynoe massive sulfide deposit are studied. Materials and methods . We used 9 samples and 15 polished sections of siliceous siltstones with pyrite mineralization. Analysis of chemical composition minerals was determined by Tescan Vega 3 with an energy dispersive microprobe Oxford Instruments X-act (Institute of Mineralogy UB RAS, Miass). Quantitave LA-ICP-MS analysis of pyrite for major and trace elements was carried out using New Wave Research UP-213 laser microprobe coupled to an Agilent 7500 quadrupole ICP-MS housed (University of Tasmania, Australia). Results. Microtopochemistry was established that the diagenetic core of the nodule is characterized by trace elements of typical poikilites of quartz (Si) and alumosilicates (Si, Al, Mg, V, Cr, K, Na, Ca), rutile and titanite (Ti), inclusions of chalcopyrite (Cu), sphalerite (Zn), galena (Pb, Sb, Bi), tetrahedrite-tennantite (As, Sb), native gold, petzite, hessite (Au, Ag, Te), tellurobismuthite, altaite, and coloradoite (Te, Bi, Pb). Cobalt and Ni substitute for Fe 2+ . The rim of subhedral pyrite is depleted in most trace elements except for Ni and As. Subhedral pyrite became rich in chalcophile (Au, Ag, Sb, Bi, Cu, Zn, Hg) and lithophile (Ca, K, Na, Cr) elements at the final stage of growth of the nodule. Similar mineralogical and geochemical zonation is typical of the pyrite metacrystals, where a micro-grained core concentrates Pb, Bi and Te, and a rim of subhedral pyrite is depleted in most trace elements. Similarly to the nodules, the outer rim of pyrite metacrystals is enriched in most trace elements (Pb, Au, Ag, Sb, Cu, As, Mo, Cr, etc.). The nodules and metacrystals were formed from diagenetic micronodule of poikilite pyrite. Conclusions. It is suggested that mineralogical and geochemical differences in pyrite metacrystals and nodules are caused by the greater degree of development of rims of subhedral pyrite.

Diagenetic variation at the lamina scale in lacustrine organic-rich shales: Implications for hydrocarbon migration and accumulation

Lacustrine carbonate-rich shales are well developed within the Mesozoic-Cenozoic strata of the Bohai Bay Basin (BBB) of eastern China and across southeast Asia. Developing an understanding of the diagenesis of these shales is essential to research on mass balance, diagenetic fluid transport and exchange, and organic-inorganic interactions in black shales. This study investigates the origin and distribution of authigenic minerals and their diagenetic characteristics, processes, and pathways at the scale of lacustrine laminae within the Es4s-Es3x shale sequence of the BBB. The research presented in this study is based on thin sections, field emission scanning electron microscope (FESEM) and SEM-catholuminescence (CL) observations of well core samples combined with the use of X-ray diffraction (XRD), energy dispersive spectroscopy, electron microprobe analysis, and carbon and oxygen isotope analyses performed using a laser microprobe mass spectrometer. The dominant lithofacies within the Es4s-Es3x sequence are a laminated calcareous shale (LCS-1) and a laminated clay shale (LCS-2). The results of this study show that calcite recrystallization1 is the overarching diagenetic process affecting the LCS-1, related to acid generation from organic matter (OM) thermal evolution. This evolutionary transition is the key factor driving the diagenesis of this lithofacies, while the transformation of clay minerals is the main diagenetic attribute of the LCS-2. Diagenetic differences occur within different laminae and at variable locations within the same lamina level, controlled by variations in mineral composition and the properties of laminae interfaces. The diagenetic fluid migration scale is vertical and responses (dissolution and replacement) are limited to individual laminae, between zero and 100 μm in width. In contrast, the dominant migration pathway for diagenetic fluid is lateral, along the abrupt interfaces between laminae boundaries, which leads to the vertical transmission of diagenetic responses. The recrystallization boundaries between calcite laminae act as the main migration pathways for the expulsion of hydrocarbons from these carbonate-rich lacustrine shales. However, because the interaction between diagenetic fluids and the shales themselves is limited to the scale of individual lamina, this system is normally closed. The occurrence of abnormal pressure fractures can open the diagenetic system, however, and cause interactions to occur throughout laminae; in particular, the closed-open (C–O) diagenetic process at this scale is critical to this shale interval. Multi-scale C–O systems are ubiquitous and episodic ranging from the scale of laminae to the whole basin. Observations show that such small-scale systems are often superimposed onto larger ones to constitute the complex diagenetic system seen within the BBB combining fluid transport, material and energy exchange, and solid-liquid and organic-inorganic interactions.

Dating palaeo‐seismic faulting in the Taiwan Mountain Belt

AbstractIn‐situ 40Ar/39Ar laser microprobe dating was carried out on the Hoping pseudotachylite from a mylonite‐fault zone in the metamorphosed basement complex of the active Taiwan Mountain Belt to determine the timing of the responsible earthquake(s). The dating results, distributed from 3.2 to 1.6 Ma with errors ranging from 0.2 to 1.1 Ma, were derived from a combination of two Ar isotopic system end‐members with inverse isochron ages of 1.55 ± 0.05 and 2.87 ± 0.07 Ma, respectively. Petrographical observations reveal fault melt containing ultracataclasites, therefore the older inverse isochron end‐member may be attributed to the relic wall rock Ar isotopic system contained in micro‐breccia. Without significant Ar loss expected, the ~1.6 Ma for the young end‐member defines the exact time of the pseudotachylite formation. Seismic faulting therefore occurred during basement rock exhumation in the Taiwanese hinterland.

Real-Time Molecular Diagnosis and Margin Definition of Tumors Based on a Novel Laser-Based Mass Spectrometry Technology

We assessed on dog sarcoma the performances of a newly developed technology, for fast ex-vivo diagnostic of tumors in the perspective to target in the future noninvasive in-vivo real-time diagnostic and excision margin definition intraoperatively, named Spidermass. The instrument is based on Mass Spectrometry (MS) molecular analysis through a laser microprobe operating under ambient condition using resonant excitation of endogenous water molecules Specificity of the molecular profiles generated with the instrument was evaluated using multivariate analysis for tumor typing or grading. Classification models based on cancer/normal, cancer/normal/necrotic, tumor grade, and cancer subtype showed at minimum of 97.63% correct classification. Specific markers of normal, cancer and necrotic regions were identified by tandem MS and validated by MS Imaging. Margins detection capabilities was studied, and compared to MS imaging and histological staining. Our results confirmed the high accuracy of the technology to differentiate between histological areas or sarcoma subtypes in real-time.

Basal accretion, a major mechanism for mountain building in Taiwan revealed in rock thermal history

Deep tectonic processes are key integral components in the evolution of mountain belts, while observations of their temporal development are generally obscured by thermal resetting, retrograde alteration and structural overprinting. Here we recorded an integrated rock time-temperature history for the first time in the pro-wedge part of the active Taiwan arc-continent collision starting from sedimentation through cleavage-forming state to its final exhumation. The integrated thermal and age results from the Raman Spectroscopy of Carbonaceous Material (RSCM) method, zircon U-Pb laser ablation dating, and in-situ40Ar/39Ar laser microprobe dating suggest that the basal accretion process was crucial to the development of the Taiwanese orogenic wedge. The basal accretion process commenced early in the mountain building history (∼6 Ma) and gradually migrated to greater depths, as constrained by persistent plate convergence and cleavage formation under nearly isothermal state at similar depths until ∼ 2.5 Ma recorded in the early-accreted units. Such development essentially contributed to mountain root growth by the increased depth of the wedge detachment and the downward wedge thickening during the incipient to full collision stages in the Taiwan mountain belt.

Growth of mica porphyroblasts under low-grade metamorphism – A Taiwanese case using in-situ40Ar/39Ar laser microprobe dating

Mica porphyroblasts, a common metamorphic microstructure, are analyzed in the slate belt of northern Taiwan where large fish-like growths are found within a meta-pyroclastics. With constraints on the time-temperature history from deposition through peak metamorphic state to exhumation, in-situ40Ar/39Ar laser microprobe dating was carried out on muscovite and corrensite fibers of mm-scale mica porphyroblasts grown on a pressure-solution seam. Because the peak metamorphic temperature and the porphyroblast formation condition (∼250 °C) remained far below the closure temperature of the K-Ar radioisotope system in muscovite, and the absence of muscovite in the mafic protolith, the dating results likely document the growth of the mica porphyroblast fabrics. The syn-kinematic nature of the analyzed porphyroblasts is confirmed by the ∼6 to ∼2.5 Ma growth ages, suggesting that the host rock was continuously deformed during the earlier two-thirds of the Taiwan Orogeny. The pattern of fiber growth, in contrast to outward-decreasing ages normally observed in peripheral recrystallization, appears random and resembles void fills in boudin openings. We postulate that syntaxial crack-seal following tensile micro-boudinage, along with slips on sub-grain boundaries, as a viable mechanism for the development of mica porphyroblasts and fish especially in lower-grade metamorphic rocks.

Tracing the Initiation of the Tribeč Mountain Exhumation by Laser-Probe 40Ar/39Ar Dating of Seismogenic Pseudotachylytes (Western Carpathians, Slovakia)

AbstractThe seismogenic pseudotachylytes from the Tribec Mountains (Western Carpathians, Slovakia) were dated by means of the laser microprobe 40Ar/39Ar method. The Tribec Mountain crystalline basement was buried to 5–7.5-km depths, where it experienced approximately >110°C and <210°C thermal conditions. The dated pseudotachylytes have spot ages between 58 ± 1 and 46 ± 1 Ma with a weighted mean age of 49.7 ± 1.3 Ma, indicating that seismic activity caused their origin, the propagation of subvertical basement marginal faults, and/or the inception of basement unroofing processes in the southern part of the Central Carpathian Paleogene Basin. The extensional tectonics were responsible for the exhumation of basement highs and the opening of the intramontane depressions on the northwest margin of the Pannonian Basin.

In-situ characterization of nanoparticle beams focused with an aerodynamic lens by Laser-Induced Breakdown Detection.

The Laser-Induced Breakdown Detection technique (LIBD) was adapted to achieve fast in-situ characterization of nanoparticle beams focused under vacuum by an aerodynamic lens. The method employs a tightly focused, 21 μm, scanning laser microprobe which generates a local plasma induced by the laser interaction with a single particle. A counting mode optical detection allows the achievement of 2D mappings of the nanoparticle beams with a reduced analysis time thanks to the use of a high repetition rate infrared pulsed laser. As an example, the results obtained with Tryptophan nanoparticles are presented and the advantages of this method over existing ones are discussed.

Refining lunar impact chronology through high spatial resolution (40)Ar/(39)Ar dating of impact melts.

Quantitative constraints on the ages of melt-forming impact events on the Moon are based primarily on isotope geochronology of returned samples. However, interpreting the results of such studies can often be difficult because the provenance region of any sample returned from the lunar surface may have experienced multiple impact events over the course of billions of years of bombardment. We illustrate this problem with new laser microprobe (40)Ar/(39)Ar data for two Apollo 17 impact melt breccias. Whereas one sample yields a straightforward result, indicating a single melt-forming event at ca. 3.83 Ga, data from the other sample document multiple impact melt-forming events between ca. 3.81 Ga and at least as young as ca. 3.27 Ga. Notably, published zircon U/Pb data indicate the existence of even older melt products in the same sample. The revelation of multiple impact events through (40)Ar/(39)Ar geochronology is likely not to have been possible using standard incremental heating methods alone, demonstrating the complementarity of the laser microprobe technique. Evidence for 3.83 Ga to 3.81 Ga melt components in these samples reinforces emerging interpretations that Apollo 17 impact breccia samples include a significant component of ejecta from the Imbrium basin impact. Collectively, our results underscore the need to quantitatively resolve the ages of different melt generations from multiple samples to improve our current understanding of the lunar impact record, and to establish the absolute ages of important impact structures encountered during future exploration missions in the inner Solar System.