Defining Multiple Characteristic Raman Bands of α-Amino Acids as Biomarkers for Planetary Missions Using a Statistical Method

Biomarker molecules, such as amino acids, are key to discovering whether life exists elsewhere in the Solar System. Raman spectroscopy, a technique capable of detecting biomarkers, will be on board future planetary missions including the ExoMars rover. Generally, the position of the strongest band in the spectra of amino acids is reported as the identifying band. However, for an unknown sample, it is desirable to define multiple characteristic bands for molecules to avoid any ambiguous identification. To date, there has been no definition of multiple characteristic bands for amino acids of interest to astrobiology. This study examinedL-alanine, L-aspartic acid, L-cysteine, L-glutamine and glycine and defined several Raman bands per molecule for reference as characteristic identifiers. Per amino acid, 240 spectra were recorded and compared using established statistical tests including ANOVA. The number of characteristic bands defined were 10, 12, 12, 14 and 19 for L-alanine (strongest intensity band: 832 cm-1), L-aspartic acid (938 cm-1), L-cysteine (679 cm-1),L-glutamine (1090 cm−1) and glycine (875 cm-1), respectively. The intensity of bands differed by up to six times when several points on the crystal sample were rotated through 360 °; to reduce this effect when defining characteristic bands for other molecules, we find that spectra should be recorded at a statistically significant number of points per sample to remove the effect of sample rotation. It is crucial that sets of characteristic Raman bands are defined for biomarkers that are targets for future planetary missions to ensure a positive identification can be made

Détection de CO2, N2, et CH4 dans les inclusions fluides de quartz d'Ardenne par microthermométrie et microsonde à effet Raman

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LASER RAMAN MICROPROBING TECHNIQUES

L'intérêt de la microspectrométrie Raman pour l'analyse moléculaire non destructive ainsi que l'évolution des techniques sont présentés. Quelques exemples d'application illustrent l'exposé.The analytical ptential of microRaman spectroscopy for non destructive molecular analysis is presented. The evolution of the techniques and some applications are presented

LE MICRODIL 28 : MICROSONDE RAMAN À DÉTECTION MULTICANALE

Nous décrivons une nouvelle génération de microsonde Raman : le Microdil 28 qui bénéficie des avantages de la détection multicanale à barrette de photodiodes intensifiée et nous présentons les avantages qui résultent de la détection simultanée des informations spectrales.We describe a new laser Raman microprobe : the Microdil 28 that benefits from the advantages of the multichannel intensified photodiodes array detector and we point out some merits resulting from its fast detection capabilities

Raman characterization of Mg⁺ ion-implanted GaN

Mg+ ions were implanted at room temperature in n-type hexagonal GaN for the device isolation purposes. The implantation dose varied from 7.5 × 1012 to 1016 ions cm-2. We performed resonance Raman spectroscopy and DC electrical measurements in order to monitor the structural and electrical changes of non-annealed and annealed implanted GaN samples. Annealing was carried out at 900 °C for 30 s, these conditions being used to achieve good Ohmic contacts. The aim was to determine, on the one hand, the influence of ion doses on the device isolation and, on the other, to establish the order of the technological steps which should be made between ion implantation and Ohmic contact annealing. On increasing the implantation dose from 7.5 × 1012 to 2 × 1014 ions cm-2, an increase in the electrical isolation and a decrease in the photoluminescence (PL) were observed. For the highest dose, the implanted layer became conductive owing to a hopping mechanism and only the first-order phonon lines remained observable. After annealing, the implanted samples became conductive and the PL reappeared or increased compared with the non-annealed samples at same implantation doses, except for the sample implanted at the highest dose, which became insulating. Then, it is possible to achieve device electrical isolation by using a lower ion dose without thermal annealing or using a higher ion dose with thermal annealing

APPLICATIONS OF THE MOLE RAMAN MICROPROBE TO THE STUDY OF FLUID INCLUSIONS IN MINERALS

Dans les inclusions fluides aqueuses, la microspectrometrie Raman permet d'analyser l'ion SO4 et d'identifier indirectement les ions monoatomiques par les hydrates de sels nucléés au cours du refroidissement. Deux exemples d'identification de gaz (CO2-H2S) et (H2-O2) dans les inclusions fluides sont présentés.In aqueous fluid inclusions, micro-Raman spectrometry allows to analyse SO4 ion and to identify indirectly monoatomic ions by the salt hydrates nucleated during cooling. Two examples of gas identification (CO2-H2S) and (H2-O2) in fluid inclusions are given

Resonant Raman scatterring study of Ar⁺ ion-implanted AlGaN

160 keV Ar+ ions were homogeneously implanted in AlGaN at room temperature for device isolation purposes. Resonance Raman spectroscopy and DC electrical measurements were used to monitor the structural and electrical changes of the non-annealed and annealed implanted AlGaN samples with a dose ranging from 3.4 × 1012 to 1 × 1016 ions cm-2. The annealing was carried out at 900 °C for 40 s, these conditions being necessary to achieve good Ohmic contacts. On increasing the implantation dose from 3.4 × 1012 to 3.4 × 1014 ions cm-2, an increase in the electrical isolation and a decrease in the photoluminescence (PL) were observed. For the highest dose, the implanted layer becomes conductive, probably due to a hopping mechanism. After annealing, the implanted samples become conductive and the PL reappears or increases as compared to the non-annealed samples using the same implantation doses. Then, it is possible to obtain good device electrical isolation by implanting ions with a 3.4 × 1014 cm-2 dose subsequently to the annealing process necessary to achieve Ohmic contacts

‘Resonant Raman scattering in Ar+ ion-implanted AlGaN’

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