Comparative study of radiation-induced damage in magnesium aluminate spinel by means of IL, CL and RBS/C techniques

International audienceA comparative study of damage accumulation in magnesium aluminate spinel (MgAl2O4) has been conducted using ionoluminescence (IL), cathodoluminescence (CL) and Rutherford Backscattering Spectrometry/channeling (RBS/C) techniques. MgAl2O4 single crystal and polycrystalline samples were irradiated with 320 keV Ar+ ions at fluencies ranging from 1 × 1012 to 2 × 1016 cm−2 in order to create various levels of radiation damage. RBS/C measurements provided quantitative data about damage concentration in the samples. These values were then compared to the luminescence measurements. The results obtained by IL and RBS/C methods demonstrate a two-step character of damage buildup process. The CL data analysis points to the three-step damage accumulation mechanism involving the first defect transformation at fluencies of about 1013 cm−2 and second at about 1015 cm−2. The rate of changes resulting from the formation of nonluminescent recombination centers is clearly nonlinear and cannot be described in terms of continuous accumulation of point defects. Both, IL and CL techniques, appear as new, complementary tools bringing new possibilities in the damage accumulation studies in single- and polycrystalline materials

Mineral maturity and crystallinity index are distinct characteristics of bone mineral

The purpose of this study was to test the hypothesis that mineral maturity and crystallinity index are two different characteristics of bone mineral. To this end, Fourier transform infrared microspectroscopy (FTIRM) was used. To test our hypothesis, synthetic apatites and human bone samples were used for the validation of the two parameters using FTIRM. Iliac crest samples from seven human controls and two with skeletal fluorosis were analyzed at the bone structural unit (BSU) level by FTIRM on sections 2–4 lm thick. Mineral maturity and crystallinity index were highly correlated in synthetic apatites but poorly correlated in normal human bone. In skeletal fluorosis, crystallinity index was increased and maturity decreased, supporting the fact of separate measurement of these two parameters. Moreover, results obtained in fluorosis suggested that mineral characteristics can be modified independently of bone remodeling. In conclusion, mineral maturity and crystallinity index are two different parameters measured separately by FTIRM and offering new perspectives to assess bone mineral traits in osteoporosis

The nature of unusual luminescence in natural calcite, CaCO3

The unusual luminescence of particular varieties of natural pink calcite (CaCO{sub 3}) samples was studied by laser-induced time-resolved luminescence spectroscopy at different temperatures. The luminescence is characterized by intense blue emission under short-wave UV lamp excitation with an extremely long decay time, accompanied by pink-orange luminescence under long wave UV excitation. Our investigation included optical absorption, natural thermostimulated luminescence (NTL) and Laser-Induced Breakdown Spectroscopy (LIBS) studies. Two luminescence centers were detected: a narrow violet band, with {lambda}{sub max} = 412 nm, {Delta} = 45 nm, two decay components of {tau}{sub 1} = 5 ns and {tau}{sub 2} = 7.2 ms, accompanied by very long afterglow, and an orange emission band with {lambda}{sub max} = 595 nm, {Delta} = 90 nm and {tau} = 5 ns. Both luminescence centers are thermally unstable with the blue emission disappearing after heating at 500 C, and the orange emission disappearing after heating at different temperatures starting from 230 C, although sometimes it is stable up to 500 C in different samples. Both centers have spectral-kinetic properties very unusual for mineral luminescence, which in combination with extremely low impurity concentrations, prevent their identification with specific impurity related emission. The most likely explanation of these observations may be the presence of radiation-induced luminescence centers. The long violet afterglow is evidently connected with trapped charge carrier liberation, with their subsequent migration through the valence band and ultimate recombination with a radiation-induced center responsible for the unusual violet luminescence

Laser-induced time-resolved luminescence of orange kyanite Al_2SiO_5

Manganese is a very important microelement performing a large number of biological functions in human body. We have detected by spectroscopic measurements manganese in mineral kyanite. In this paper we present laser-induced time-resolved luminescence and optical absorbance spectra of orange, Mn containing kyanite. It was proven the orange color is caused by Mn^(3+). Several luminescence lines and bands were found and ascribed to Mn^(4+) and Mn^(3+), emission centers. The spectroscopic technique can be utilized for detection of small amounts of manganese in minerals

Etude taphonomique des sols et des parois, Grotte Chauvet

Rapport annue

Red photoluminescence and purple color of naturally irradiated fluorite

Natural radiation-induced red fluorescence of fluorite consists of two broad bands at 750 and 635 nm with very short decay times of 20.3 and less than 5 ns, respectively. The first one is connected to an M center compensated by Na, while the second is connected to an M⁺ center, possibly formed as result of the M center’s destruction by UV irradiation. The optically active centers in naturally irradiated fluorite responsible for red luminescence and purple color are different from one another. The most probable reason for the purple color is colloidal calcium and not the M_(Na) center

Red photoluminescence and purple color of naturally irradiated fluorite

Natural radiation-induced red fluorescence of fluorite consists of two broad bands at 750 and 635 nm with very short decay times of 20.3 and less than 5 ns, respectively. The first one is connected to an M center compensated by Na, while the second is connected to an M⁺ center, possibly formed as result of the M center’s destruction by UV irradiation. The optically active centers in naturally irradiated fluorite responsible for red luminescence and purple color are different from one another. The most probable reason for the purple color is colloidal calcium and not the M_(Na) center

Luminescence analysis of damage accumulation; case study of calcium molybdate

International audienceA comparative study of damage accumulation in calcium molybdate (CaMoO4) has been conducted using Rutherford Backscattering/Channeling (RBS/C), cathodoluminescence (CL) and ionoluminescence (IL) techniques. All methods used confirm a two-step character of damage build-up process. Similar threshold fiuence values have been extracted from RBS/C, CL and IL measurements. This analysis confirms the huge potential of luminescence techniques for damage analysis in single- and polycrystalline samples and the ability of the IL method to perform fast, in situ analysis of damage accumulation process. (C) 2014 Elsevier B.V. All rights reserved

Exploration of megapixel hyperspectral LIBS images using principal component analysis

Laser-Induced Breakdown Spectroscopy (LIBS) has achieved promising performance as an elemental imaging technology, and considerable progress has been achieved in the development of LIBS over the last several years, which has led to great interest in the use of LIBS in various fields of applications. LIBS is a highly attractive technology that is distinguished by its table top instrumentation, speed of operation, and operation in ambient atmosphere, able to produce megapixel multi-elemental images with micrometric resolution (10 μm) and ppm-scale sensitivity. However, the points that limit the development of LIBS are undeniably the expertise and the time required to extract a relevant signal from the LIBS dataset. The complexity of the emission spectra (e.g., elemental responses, structure of the baseline), the high dynamic range of measurement (i.e., possibility to image major to trace elements), and the large number of spectra to process require new data analysis strategies. Such new strategies are particularly critical for multi-phase materials. In this paper, we report a new methodology based on the well-known Principal Component Analysis (PCA) approach for the multivariate hyperspectral analysis of LIBS images. The proposed methodology is designed for large, raw, and potentially complex series of LIBS spectra, that allows various and exhaustive levels of information to be extracted (including the characterization of mineral phases, assessment of the measurement and identification of isolated elements) and facilitates the manipulation of such hyperspectral datasets

Mapping of native inorganic elements and injected nanoparticles in a biological organ with laser-induced plasma

International audienceEmission spectroscopy of laser-induced plasma from a thin section of mouse kidney successfully detected inorganic elements, Na, Ca, Cu, and Gd, naturally contained in the organ or artificially injected in the form of Gd-based nanoparticle. A two-dimensional scan of the sample allowed the laser beam to explore its surface with a resolution of 100 μm, resulting in a quantitative elemental mapping of the organ with sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes the potential to provide multiple images of a same biological tissue with different types of response which can be elemental, molecular, or cellular