Quantitative laser-matter interaction: a 3D study of UV-fs-laser ablation on single crystalline Ru(0001).

Laser ablation is nowadays an extensively applied technology to probe the chemical composition of solid materials. It allows for precise targeting of micrometer objects on and in samples, and enables chemical depth profiling with nanometer resolution. An in-depth understanding of the 3D geometry of the ablation craters is crucial for precise calibration of the depth scale in chemical depth profiles. Herein we present a comprehensive study on laser ablation processes using a Gaussian-shaped UV-femtosecond irradiation source and present how the combination of three different imaging methods (scanning electron microscopy, interferometric microscopy, and X-ray computed tomography) can provide accurate information on the crater's shapes. Crater analysis by applying X-ray computed tomography is of considerable interest because it allows the imaging of an array of craters in one step with sub-µm accuracy and is not limited to the aspect ratio of the crater. X-ray computed tomography thereby complements the analysis of laser ablation craters. The study investigates the effect of laser pulse energy and laser burst count on a single crystal Ru(0001) sample. Single crystals ensure that there is no dependence on the grain orientations during the laser ablation process. An array of 156 craters of different dimensions ranging from <20 nm to ∼40 µm in depth were created. For each individually applied laser pulse, we measured the number of ions generated in the ablation plume with our laser ablation ionization mass spectrometer. We show to which extent the combination of these four techniques reveals valuable information on the ablation threshold, the ablation rate, and the limiting ablation depth. The latter is expected to be a consequence of decreasing irradiance upon increasing crater surface area. The ion signal generated was found to be proportional to the volume ablated up to the certain depth, which enables in-situ depth calibration during the measurement.

Reduction of surface charging effects in laser ablation ionisation mass spectrometry through gold coating.

In femtosecond Laser Ablation Ionisation Mass Spectrometry (fs-LIMS) short laser pulses are used to ablate, atomise, and ionise solid sample material shot-by-shot. When ablating non-conductive samples electric charging of the surface can occur. Depending on the geometry of the instrument, the surface charge can influence the spread of the ablation plume and reduce spectral quality. Methods to reduce surface charging were investigated using a non-conductive geological sample and a miniature fs-LIMS system with a co-linear ablation geometry. Pausing five seconds between consecutive laser bursts fired on non-coated material improved the spectral quality by giving surface charges more time to dissipate. However, best mass spectrometric results were achieved after the sample was sputter coated with a thin gold layer, as a conductive sample surface hinders charge build-up. Consequently, gold coating allowed operation of the laser system at much higher laser pulse energies improving sensitivity and reliability. It also removed the need to pause between laser bursts, speeding up the measurement acquisition.

Improved plasma stoichiometry recorded by laser ablation ionization mass spectrometry using a double-pulse femtosecond laser ablation ion source.

RATIONALE: Femtosecond (fs) laser ablation ion sources have allowed for improved measurement capabilities and figures of merit of laser ablation based spectroscopic and mass spectrometric measurement techniques. However, in comparison to longer pulse laser systems, the ablation plume from fs lasers is observed to be colder, which favors the formation of polyatomic species. Such species can limit the analytical capabilities of a system due to isobaric interferences. In this contribution, a double-pulse femtosecond (DP-fs) laser ablation ion source is coupled to our miniature Laser Ablation Ionization Mass Spectrometry (LIMS) system and its impact on the recorded stoichiometry of the generated plasma is analyzed in detail. METHODS: A DP-fs laser ablation ion source (temporal delays of +300 to - 300 ps between pulses) is connected to our miniature LIMS system. The first pulse is used for material removal from the sample surface and the second for post-ionization of the ablation plume. To characterize the performance, parametric double- and single-pulse studies (temporal delays, variation of the pulse energy, voltage applied on detector system) were conducted on three different NIST SRM alloy samples (SRM 661, 664 and 665). RESULTS: At optimal instrument settings for both the double-pulse laser ablation ion source and the detector voltage, relative sensitivity coefficients were observed to be closer (factor of ~2) to 1 compared with single-pulse measurements. Furthermore, the optimized settings worked for all three samples, meaning no further optimization was necessary when changing to another alloy sample material during this study. CONCLUSIONS: The application of a double-pulse femtosecond laser ablation ion source resulted in the recording of improved stoichiometry of the generated plasma using our LIMS measurement technique. This is of great importance for the quantitative chemical analysis of more complex solid materials, e.g., geological samples or metal alloys, especially when aiming for standard-free quantification procedures for the determination of the chemical composition.

UV post-ionization laser ablation ionization mass spectrometry for improved nm-depth profiling resolution on Cr/Ni reference standard.

RATIONALE: Laser ablation combined with mass spectrometry forms a promising tool for chemical depth profiling of solids. At irradiations near the ablation threshold, high depth resolutions are achieved. However, at these conditions, a large fraction of ablated species is neutral and therefore invisible to the instrument. To compensate for this effect, an additional ionization step can be introduced. METHODS: Double-pulse laser ablation is frequently used in material sciences to produce shallow craters. We apply double-pulse UV femtosecond (fs) Laser Ablation Ionization Mass Spectrometry to investigate the depth profiling performance. The first pulse energy is set to gentle ablation conditions, whereas the second pulse is applied at a delay and a pulse energy promoting the highest possible ion yield. RESULTS: The experiments were performed on a Cr/Ni multi-layered standard. For a mean ablation rate of ~3 nm/pulse (~72 nJ/pulse), a delay of ~73 ps provided optimal results. By further increasing the energy of the second pulse (5-30% higher with respect to the first pulse) an enhancement of up to 15 times the single pulse intensity was achieved. These conditions resulted in mean depth resolutions of ~37 and ~30 nm for the Cr and Ni layers, respectively. CONCLUSIONS: It is demonstrated on the thin-film standard that the double-pulse excitation scheme substantially enhances the chemical depth profiling resolution of LIMS with respect to the single-pulse scheme. The post-ionization allows for extraordinarily low ablation rates and for quantitative and stoichiometric analysis of nm-thick films/coatings.

Combining Anisotropic Etching and PDMS Casting for Three-Dimensional Analysis of Laser Ablation Processes.

State-of-the-art laser ablation (LA) depth-profiling techniques (e.g. LA-ICP-MS, LIBS, and LIMS) allow for chemical composition analysis of solid materials with high spatial resolution at micro- and nanometer levels. Accurate determination of LA-volume is essential to correlate the recorded chemical information to the specific location inside the sample. In this contribution, we demonstrate two novel approaches towards a better quantitative analysis of LA craters with dimensions at micrometer level formed by femtosecond-LA processes on single-crystalline Si(100) and polycrystalline Cu model substrates. For our parametric crater evolution studies, both the number of applied laser shots and the pulse energy were systematically varied, thus yielding 2D matrices of LA craters which vary in depth, diameter, and crater volume. To access the 3D structure of LA craters formed on Si(100), we applied a combination of standard lithographic and deep reactive-ion etching (DRIE) techniques followed by a HR-SEM inspection of the previously formed crater cross sections. As DRIE is not applicable for other material classes such as metals, an alternative and more versatile preparation technique was developed and applied to the LA craters formed on the Cu substrate. After the initial LA treatment, the Cu surface was subjected to a polydimethylsiloxane (PDMS) casting process yielding a mold being a full 3D replica of the LA craters, which was then analyzed by HR-SEM. Both approaches revealed cone-like shaped craters with depths ranging between 1 and 70 µm and showed a larger ablation depth of Cu that exceed the one of Si by a factor of about 3.

Insights into Laser Ablation Processes of Heterogeneous Samples: Toward Analysis of Through-Silicon-Vias.

State-of-the-art three-dimensional very large-scale integration (3D-VLSI) relies, among other factors, on the purity of high-aspect-ratio Cu interconnects such as through-silicon-vias (TSVs). Accurate spatial chemical analysis of electroplated TSV structures has been proven to be challenging due to their large aspect ratios and their multimaterial composition (Cu and Si) with distinct physical properties. Here, we demonstrate that these structures can be accurately analyzed by femtosecond (fs) laser beam ablation techniques in combination with ionization mass spectrometry (LIMS). We specifically report on novel preparation approaches for the postablation analysis of craters formed upon TSV depth profiling. The novel TSV sample preparation is based on deep and material-selective reactive-ion etching of the Si matrix surrounding the Cu interconnects thus facilitating systematic focused-ion-beam (FIB) investigations of the high-aspect-ratio TSV structures upon ablation. The particular structure of the TSV analyte combined with the ⌀beam > ⌀Cu-TSV condition allowed for an in-depth investigation of fundamental laser ablation processes, particularly focusing on the redeposition of ablated material at the inner side-walls of the LIMS craters. This phenomenon is of imminent importance for the ultimate quantification in any laser ablation-based depth profiling. In addition, we have developed a new method which allows the unambiguous determination of the crossing-point of the Si/Cu||bare Si interface upon Cu-TSV depth profiling which is based on pronounced, depth-dependent changes in the mass-spectrometric detection of those Si xy+ species formed upon the LIMS depth erosion.

Depth Profiling and Cross-Sectional Laser Ablation Ionization Mass Spectrometry Studies of Through-Silicon-Vias.

Through-silicon-via (TSV) technology enables 3D integration of multiple 2D components in advanced microchip architectures. Key in the TSV fabrication is an additive-assisted Cu electroplating process in which the additives employed may get embedded in the TSV body. This incorporation negatively influences the reliability and durability of the Cu interconnects. Here, we present a novel approach toward the chemical analysis of TSVs which is based on femtosecond laser ablation ionization mass spectrometry (fs-LIMS). The conditions for LIMS depth profiling were identified by a systematic variation of the laser pulse energy and the number of laser shots applied. In this contribution, new aspects are addressed related to the analysis of highly heterogeneous specimens having dimensions in the range of the probing beam itself. Particularly challenging were the different chemical and physical properties of which the target specimens were composed. Depth profiling of the TSVs along their main axis (approach 1) revealed a gradient in the carbon (C) content. These differences in the C concentration inside the TSVs could be confirmed and quantified by LIMS analyses of cross-sectionally sliced TSVs (approach 2). Our quantitative analysis revealed a C content that is ∼1.5 times higher at the TSV top surface compared to its bottom. Complementary Scanning Auger Microscopy (SAM) data confirmed a preferential embedment of suppressor additives at the side walls of the TSV. These results demonstrate that the TSV filling concept significantly deviates from common Damascene electroplating processes and will therefore contribute to a more comprehensive, mechanistic understanding of the underlying mechanisms.

Toward Three-Dimensional Chemical Imaging of Ternary Cu-Sn-Pb Alloys Using Femtosecond Laser Ablation/Ionization Mass Spectrometry.

Femtosecond laser ablation/ionization mass spectrometry (LIMS) has been applied to probe the spatial element composition of three ternary Cu-Sn-Pb model bronze alloys (lead bronzes: CuSn10Pb10, CuSn7Pb15, and CuSn5Pb20), which were recently identified as high-performance cathode materials in the context of electro-organic synthesis (dehalogenation, deoxygenation) of pharmaceutically relevant building blocks. The quantitative and spatially resolved element analysis of such cathode materials will help in understanding the observed profound differences in their electrochemical reactivity and stability. For that purpose, we developed a measurement procedure using the LIMS technique which allows analyzing the element composition of these ternary alloys in all three spatial dimensions. Their chemical composition was determined spotwise, by ablating material from various surface locations on a 4 × 4 raster array (50 µm pitch distance, ablation crater diameter of ∼20 µm). The element analyses show significant chemical inhomogeneities in all three ternary bronze alloys with profound local deviations from their nominal bulk compositions and indicate further differences in the nature and origin of these compositional inhomogeneities. In addition, the element analyses showed specific compositional correlations among the major elements (Cu, Sn, and Pb) in these alloys. On selected sample positions minor (Ni, Zn, Ag, and Sb) and trace elements (C, P, Fe, and As) were quantified. These results are in agreement with inductively coupled plasma collision/reaction interface mass spectrometry (ICP-CRI-MS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) reference measurements, thus proving the LIMS depth profiling technique as a powerful alternative methodology to conventional quantification techniques with the advantage, however, of a highly localized measurement capability.

Towards matrix-free femtosecond-laser desorption mass spectrometry for in situ space research.

RATIONALE: There is an increasing interest in the quest for low molecular weight biomarkers that can be studied on extra-terrestrial objects by direct laser desorption mass spectrometry (LD-MS). Although molecular structure investigations have recently been carried out by direct LD-MS approaches, there is still a lack of suitable instruments for implementation on a spacecraft due to weight, size and power consumption demands. In this contribution we demonstrate the feasibility of LD-MS structural analysis of molecular species by a miniature laser desorption-ionization mass spectrometer (instrument name LMS) originally designed for in situ elemental and isotope analysis of solids in space research. METHODS: Direct LD-MS studies with molecular resolution were carried out by means of a Laser Ablation/Ionization Mass Spectrometry (LIMS) technique. Two polymer samples served as model systems: neutral polyethylene glycol (PEG) and cationic polymerizates of imidazole and epichlorohydrin (IMEP). Optimal conditions for molecular fragmentation could be identified for both polymers by tuning the laser energy and the instrument-sample distance. RESULTS: PEG and IMEP polymers show sufficient stability over a relatively wide laser energy range. Under mild LD conditions only moderate fragmentation of the polymers takes place so that valuable structural characterization based on fragment ions can be achieved. As the applied laser pulse energy rises, the abundance of fragment ions increases, reaches a plateau and subsequently drops down due to more severe fragmentation and atomization of the polymers. At this final stage, usually referred to as laser ablation, only elemental/isotope analysis can be achieved. CONCLUSIONS: Our investigations demonstrate the versatility of the LMS instrument that can be tuned to favourable laser desorption conditions that successfully meet molecule-specific requirements and deliver abundant fragment ion signals with detailed structural information. Overall, the results show promise for use in similar studies on planetary surfaces beyond Earth where no or minimal sample preparation is essential.

Laser Ablation/Ionisation Mass Spectrometry: Sensitive and Quantitative Chemical Depth Profiling of Solid Materials.

Direct quantitative and sensitive chemical analysis of solid materials with high spatial resolution, both in lateral and vertical direction is of high importance in various fields of analytical research, ranging from in situ space research to the semiconductor industry. Accurate knowledge of the chemical composition of solid materials allows a better understanding of physical and chemical processes that formed/altered the material and allows e.g. to further improve these processes. So far, state-of-the-art techniques such as SIMS, LA-ICP-MS or GD-MS have been applied for chemical analyses in these fields of research. In this report we review the current measurement capability and the applicability of our Laser Ablation/Ionisation Mass Spectrometer (instrument name LMS) for the chemical analysis of solids with high spatial resolution. The most recent chemical analyses conducted on various solid materials, including e.g. alloys, fossils and meteorites are discussed.

High-resolution chemical depth profiling of solid material using a miniature laser ablation/ionization mass spectrometer.

High-resolution chemical depth profiling measurements of copper films are presented. The 10 µm thick copper test samples were electrodeposited on a Si-supported Cu seed under galvanostatic conditions in the presence of particular plating additives (SPS, Imep, PEI, and PAG) used in the semiconductor industry for the on-chip metallization of interconnects. To probe the trend of these plating additives toward inclusion into the deposit upon growth, quantitative elemental mass spectrometric measurements at trace level concentration were conducted by using a sensitive miniature laser ablation ionization mass spectrometer (LIMS), originally designed and developed for in situ space exploration. An ultrashort pulsed laser system (τ ∼ 190 fs, λ = 775 nm) was used for ablation and ionization of sample material. We show that with our LIMS system, quantitative chemical mass spectrometric analysis with an ablation rate at the subnanometer level per single laser shot can be conducted. The measurement capabilities of our instrument, including the high vertical depth resolution coupled with high detection sensitivity of ∼10 ppb, high dynamic range ≥10(8), measurement accuracy and precision, is of considerable interest in various fields of application, where investigations with high lateral and vertical resolution of the chemical composition of solid materials are required, these include, e.g., wafers from semiconductor industry or studies on space weathered samples in space research.

LIF spectrum for the localised S0 → S1(ππ*) excitation in the H-bonded anthranilic acid dimer: Symmetry breaking or coupling of vibrations.

This study aims to investigate the impact of the π â†’ π* excitation localised in one monomer on the equilibrium geometry and oscillations of the AA dimer. Several low-frequency vibrations appear in pairs in the LIF spectrum because oscillations involving intermolecular hydrogen bonds are coupled, generating approximately symmetric and antisymmetric combinations (especially the COOH rocking modes, LIF: 295 and 301 cm-1). Furthermore, quantitative evaluation based on the TDDFT(B3LYP) results indicates that a dozen among 90 intramolecular oscillations are strongly coupled. In contrast, most vibrations are decoupled or weakly coupled, since they involve remote parts of the monomers. This makes several single vibrations active in the LIF spectrum (including the bending mode of the NH···O intramolecular hydrogen bond associated the strongest vibronic band 442 cm-1), while the other in each pair remains inactive. The reason for decoupling of oscillations and symmetry breaking is that the π â†’ π* electronic excitation is entirely localised within one of the monomers, which makes them no longer equivalent in terms of geometry and dynamics. Additionally, the excitation of one monomer induces strengthening and shortening by 6 pm of only one intermolecular hydrogen bond linking the carboxylic groups of both molecules. This causes the 1.7° in-plane distortion of the dimer and lowering of its symmetry to Cs group (from C2h for the S0 state). The distortion induces the activity of two low-frequency in-plane intermolecular vibrations, i.e. the geared oscillation (LIF: 58 cm-1) and the shearing motion (99 cm-1) of the monomers.

Multiwavelength Ablation/Ionization and Mass Spectrometric Analysis of 1.88 Ga Gunflint Chert.

The investigation of chemical composition on planetary bodies without significant sample processing is of importance for nearly every mission aimed at robotic exploration. Moreover, it is a necessary tool to achieve the longstanding goal of finding evidence of life beyond Earth, for example, possibly preserved microbial remains within martian sediments. Our Laser Ablation Ionization Mass Spectrometer (LIMS) is a compact time-of-flight mass spectrometer intended to investigate the elemental, isotope, and molecular composition of a wide range of solid samples, including e.g., low bulk density organic remains in microfossils. Here, we present an overview of the instrument and collected chemical spectrometric data at the micrometer level from a Precambrian chert sample (1.88 Ga Gunflint Formation, Ontario, Canada), which is considered to be a martian analogue. Data were collected from two distinct zones-a silicified host area and a carbon-bearing microfossil assemblage zone. We performed these measurements using an ultrafast pulsed laser system (pulse width of ∼180 fs) with multiple wavelengths (infrared [IR]-775 nm, ultraviolet [UV]-387 nm, UV-258 nm) and using a pulsed high voltage on the mass spectrometer to reveal small organic signals. We investigated (1) the chemical composition of the sample and (2) the different laser wavelengths' performance to provide chemical depth profiles in silicified media. Our key findings are as follows: (1) microfossils from the Gunflint chert reveal a distinct chemical composition compared with the host mineralogy (we report the identification of 24 elements in the microfossils); (2) detection of the pristine composition of microfossils and co-occurring fine chemistry (rare earth elements) requires utilization of the depth profiling measurement protocol; and (3) our results show that, for analysis of heterogeneous material from siliciclastic deposits, siliceous sinters, and cherts, the most suitable wavelength for laser ablation/Ionization is UV-258 nm.

Characterization of C4H in the A2Π and X2Σ+ states by double resonance four-wave mixing.

The B(2)Π-X(2)Σ(+) electronic spectrum of C(4)H has been studied by degenerate and double resonance four-wave mixing. The technique identifies vibrational levels in the X(2)Σ(+) ground state. Its sensitivity and unique characteristics permit detection of new levels. The A(2)Π state lying 222 cm(-1) above the X(2)Σ ground state is also observed, confirming the analysis from anion photoelectron spectroscopy but with improved accuracy. Vibrational level determination in the A(2)Π electronic manifold up to 700 cm(-1) above v = 0 is made. A Renner-Teller analysis is carried out for the two lowest bending modes v(6) and v(7) in the A(2)Π state by diagonalization of the effective Hamiltonian matrix. The Renner-Teller parameters ∈(6), ∈(7), and ∈(67), the vibrations ω(6) and ω(7) and the spin-orbit coupling constant A(so) are determined.

On Topological Analysis of fs-LIMS Data. Implications for in Situ Planetary Mass Spectrometry.

In this contribution, we present results of non-linear dimensionality reduction and classification of the fs laser ablation ionization mass spectrometry (LIMS) imaging dataset acquired from the Precambrian Gunflint chert (1.88 Ga) using a miniature time-of-flight mass spectrometer developed for in situ space applications. We discuss the data generation, processing, and analysis pipeline for the classification of the recorded fs-LIMS mass spectra. Further, we define topological biosignatures identified for Precambrian Gunflint microfossils by projecting the recorded fs-LIMS intensity space into low dimensions. Two distinct subtypes of microfossil-related spectra, a layer of organic contamination and inorganic quartz matrix were identified using the fs-LIMS data. The topological analysis applied to the fs-LIMS data allows to gain additional knowledge from large datasets, formulate hypotheses and quickly generate insights from spectral data. Our contribution illustrates the utility of applying spatially resolved mass spectrometry in combination with topology-based analytics in detecting signatures of early (primitive) life. Our results indicate that fs-LIMS, in combination with topological methods, provides a powerful analytical framework and could be applied to the study of other complex mineralogical samples.

Rotationally resolved ground state vibrational levels of HC2S studied by two-color resonant four-wave mixing.

A high-resolution study of the X(2)Pi(3/2) ground state rovibronic energy levels of jet-cooled HC(2)S radical using the double-resonance two-color four-wave mixing technique (TC-RFWM) is reported. The rotational structure of the bands is observed by excitation of selected R-branch lines in the origin band of the A(2)Pi(3/2)-X(2)Pi(3/2) electronic system. The second laser frequency is scanned to transfer the population from the rotational level(s) of the upper state to selected vibronic levels of the ground state. Fourteen rotationally resolved vibrational bands have been recorded for energies up to 1800 cm(-1) above the v'' = 0 X(2)Pi(3/2) electronic ground state. Effective rotational constants and origins are determined for levels that involve fundamental and overtone combinations of the nu(3) (CS stretch), nu(4) (CCH bend), and nu(5) (CCS bend) vibrations. This illustrates the power and advantages of the TC-RFWM approach for the study of the ground state manifold of reactive intermediates produced in low concentrations with high resolution, good signal-to-noise and wide dynamic range.

Isotope abundance ratio measurements using femtosecond laser ablation ionization mass spectrometry.

Accurate isotope ratio measurements are of high importance in various scientific fields, ranging from radio isotope geochronology of solids to studies of element isotopes fractionated by living organisms. Instrument limitations, such as unresolved isobaric inferences in the mass spectra, or cosampling of the material of interest together with the matrix material may reduce the quality of isotope measurements. Here, we describe a method for accurate isotope ratio measurements using our laser ablation ionization time-of-flight mass spectrometer (LIMS) that is designed for in situ planetary research. The method is based on chemical depth profiling that allows for identifying micrometer scale inclusions embedded in surrounding rocks with different composition inside the bulk of the sample. The data used for precise isotope measurements are improved using a spectrum cleaning procedure that ensures removal of low quality spectra. Furthermore, correlation of isotopes of an element is used to identify and reject the data points that, for example, do not belong to the species of interest. The measurements were conducted using IR femtosecond laser irradiation focused on the sample surface to a spot size of ~12 µm. Material removal was conducted for a predefined number of laser shots, and time-of-flight mass spectra were recorded for each of the ablated layers. Measurements were conducted on NIST SRM 986 Ni isotope standard, trevorite mineral, and micrometer-sized inclusions embedded in aragonite. Our measurements demonstrate that element isotope ratios can be measured with accuracies and precision at the permille level, exemplified by the analysis of B, Mg, and Ni element isotopes. The method applied will be used for in situ investigation of samples on planetary surfaces, for accurate quantification of element fractionation induced by, for example, past or present life or by geochemical processes.

The Detection of Elemental Signatures of Microbes in Martian Mudstone Analogs Using High Spatial Resolution Laser Ablation Ionization Mass Spectrometry.

The detection and identification of biosignatures on planetary bodies such as Mars in situ is extremely challenging. Current knowledge from space exploration missions suggests that a suite of complementary instruments is required in situ for a successful identification of past or present life. For future exploration missions, new and innovative instrumentation capable of high spatial resolution chemical (elemental and isotope) analysis of solids with improved measurement capabilities is of considerable interest because a multitude of potential signatures of extinct or extant life have dimensions on the micrometer scale. The aim of this study is to extend the current measurement capabilities of a miniature laser ablation ionization mass spectrometer (LIMS) designed for space exploration missions to detect signatures of microbial life. In total, 14 martian mudstone analogue samples were investigated regarding their elemental composition. Half the samples were artificially inoculated with a low number density of microbes, and half were used as abiotic controls. The samples were treated in a number of ways. Some were cultured anaerobically and some aerobically; some abiotic samples were incubated with water, and some remained dry. Some of the samples were exposed to a large dose of γ radiation, and some were left un-irradiated. While no significant elemental differences were observed between the applied sample treatments, the instrument showed the capability to detect biogenic element signatures of the inoculated microbes by monitoring biologically relevant elements, such as hydrogen, carbon, sulfur, iron, and so on. When an enrichment in carbon was measured in the samples but no simultaneous increase in other biologically relevant elements was detected, it suggests, for example, a carbon-containing inclusion; when the enrichment was in carbon and in bio-relevant elements, it suggests the presences of microbes. This study presents first results on the detection of biogenic element patterns of microbial life using a miniature LIMS system designed for space exploration missions.

ORIGIN: a novel and compact Laser Desorption - Mass Spectrometry system for sensitive in situ detection of amino acids on extraterrestrial surfaces.

For the last four decades space exploration missions have searched for molecular life on planetary surfaces beyond Earth. Often pyrolysis gas chromatography mass spectrometry has been used as payload on such space exploration missions. These instruments have relatively low detection sensitivity and their measurements are often undermined by the presence of chloride salts and minerals. Currently, ocean worlds in the outer Solar System, such as the icy moons Europa and Enceladus, represent potentially habitable environments and are therefore prime targets for the search for biosignatures. For future space exploration missions, novel measurement concepts, capable of detecting low concentrations of biomolecules with significantly improved sensitivity and specificity are required. Here we report on a novel analytical technique for the detection of extremely low concentrations of amino acids using ORIGIN, a compact and lightweight laser desorption ionization - mass spectrometer designed and developed for in situ space exploration missions. The identified unique mass fragmentation patterns of amino acids coupled to a multi-position laser scan, allows for a robust identification and quantification of amino acids. With a detection limit of a few fmol mm-2, and the possibility for sub-fmol detection sensitivity, this measurement technique excels current space exploration systems by three orders of magnitude. Moreover, our detection method is not affected by chemical alterations through surface minerals and/or salts, such as NaCl that is expected to be present at the percent level on ocean worlds. Our results demonstrate that ORIGIN is a promising instrument for the detection of signatures of life and ready for upcoming space missions, such as the Europa Lander.

Selective detection of radicals and ions in a slit-jet discharge by degenerate and two-color four-wave mixing.

Degenerate four-wave mixing (DFWM) was used to record the spectra of charged and neutral carbon-containing radicals generated in a pulsed discharge source within a supersonic slit-jet expansion. Detection limits of approximately 10(9) molecules cm(-3) are achieved. The DFWM method allows a selective molecular detection by varying the discharge timings. Increased spectral selectivity is obtained by applying the two-color, doubly resonant four-wave mixing variant. This shows the potential of the techniques for sensitive and selective spectral analysis of radicals in discharges. The methods are successfully used for the detection of C(4)H, HC(2)S, and HC(4)H(+) with signal-to-noise in the range of 10(2)-10(4).