Obtaining Raman spectra of minerals and carbonaceous matter using a portable sequentially shifted excitation Raman spectrometer – a few examples

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Fumaroles, vents that emit hot gases and vapor, are an accompanying phenomenon of volcanic activity. Such phenomena are also observed within the framework of self‐ignited burning coal seams and coal heap fires, if less commonly. The high temperatures and chemical reactions between the gas and solid phases are responsible for extensive alteration of surrounding rocks, resulting in mineral encrustations of unusual compositions. Rare anhydrous sulfates (millosevichite, mikasaite, efremovite, godovikovite, sabieite, and steklite) are signature minerals of fumarole encrustations. Comprehensive Raman data for these anhydrous phases are required for the successful identification of natural samples by Raman spectroscopy. Six synthetic equivalents of the natural anhydrous sulfates were prepared by heating of the hydrated analogues and were investigated using both a bench‐top Raman microspectrometer and a portable Raman spectrometer. This comparative approach can help further steps for the successful deployments of miniature Raman tools in situ under field conditions. The studied anhydrous sulfates displayed distinctive Raman spectra of their crystalline phases. Compared with their fully hydrated counterparts, a shifting of bands of the ν1 symmetric stretching mode was observed in the Raman spectra of all samples. Isostructural millosevichite and mikasaite have very distinctive Raman spectra; however, structurally related godovikovite, sabieite, and steklite show very similar spectral shapes. For ammonium‐bearing phases (efremovite, godovikovite, sabieite), the Raman signatures of the NH4 group were observable at >2,800 cm−1 and in the 1,400–1,800 cm−1 region. Our measurements show that the performance of a light‐weight portable Raman spectrometer with near infrared excitation was sufficient for the unambiguous discrimination of the investigated sulfates.

Section: Discussionmentioning

confidence: 99%

Raman spectroscopic study of six synthetic anhydrous sulfates relevant to the mineralogy of fumaroles

Košek

Culka

Jehlička

2018

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“…Therefore, the final Raman spectrum is produced from the six “raw” spectra containing both the Raman and fluorescence bands. This method is described in greater detail in Jehlička et al, 2017 …”

Section: Methodsmentioning

confidence: 99%

“…Conti et al, 2016 and Vagnini et al, 2017 have studied both organic and inorganic pigments used in works of arts. Carbonaceous matter and minerals, cut minerals, and gemstones, as well as emeralds and other beryl varieties have been successfully studied recently using a SSE‐equipped portable instrument …”

Section: Introductionmentioning

confidence: 99%

“…Conti et al, 2016 [10] and Vagnini et al, 2017 [11] have studied both organic and inorganic pigments used in works of arts. Carbonaceous matter and minerals, [12] cut minerals, and gemstones, [13] as well as emeralds and other beryl varieties have been successfully studied recently using a SSE-equipped portable instrument. [14] In our previous in situ, geological and mineralogical studies [7,8,15] performed using a portable Raman spectrometer (Inspector Raman with the 785 nm excitation), several light-colored minerals (anhydrite, apatite) as well as zircon often manifested variable, often very intense, laserinduced fluorescence.…”

Section: Introductionmentioning

confidence: 99%

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Sequentially shifted excitation: A tool for suppression of laser‐induced fluorescence in mineralogical applications using portable Raman spectrometers

Culka

Jehlička

2018

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Laser‐induced fluorescence is a phenomenon that can be encountered in the Raman spectra of minerals, and it complicates the acquisition of high quality Raman spectra when using portable instruments. A novel portable Raman spectrometer utilizing sequentially shifted excitation was used for analyses of the minerals anhydrite, apatite, and zircon that frequently exhibit laser‐induced fluorescence, especially when 785 nm excitation is used. Fluorescence centers, responsible for the laser‐induced fluorescence in these minerals, are generated primarily by the presence of rare earth elements. The narrow and intense fluorescence bands that arise can be confused with or mask the Raman bands of the minerals when analyzing with the conventional 785 nm excitation. It has been found that the fluorescence is completely removed in those spectral regions containing no Raman bands of the minerals. In the areas of those Raman spectra of minerals where the fluorescence and Raman bands coincide, the sequentially shifted excitation was able to suppress effectively the fluorescence. In some cases, the fluorescence removal process in the final spectra of the most fluorescence samples introduced new instrumental artifact bands. Nevertheless, the sequentially shifted excitation was able to suppress this specific laser‐induced fluorescence quite effectively; and Raman features became well pronounced, especially for the zircon specimens. This novel approach of obtaining high quality Raman spectra of minerals containing trace amounts of fluorescence‐inducing components (such as rare earth elements) with portable instrumentation opens up new possibilities for in situ spectroscopic analyses in the fields of mineralogy and geology.

“…Jehlicka, Culka, and Kosek described measuring Raman spectra of minerals and carbonaceous matter using a portable sequentially shifted excitation Raman spectrometer. They provided examples of application of a recently developed portable sequentially shifted excitation Raman spectrometer for identifying three series minerals and carbonaceous matter . Lopez‐Reyes and Rull Perez reported a method for automated Raman spectral acquisition.…”

Section: Raman Techniques and Methodsmentioning

confidence: 99%

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

Nafie

2018

This annual review is an overview of advances in the field of Raman spectroscopy as found in papers published in the previous calendar year in the Journal of Raman Spectroscopy (JRS), as well as in trends over the past decade across journals that have published papers important to the field of Raman spectroscopy. This information is gleaned from statistical data on article counts obtained from the Clarivate Analytic's Web of Science Core Collection by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations at the XXVI International Conference on Raman Spectroscopy (ICORS 2018) in Jeju Island, Korea in August 2018, and contributions on Raman scattering at SCIX 2018, organized by the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS) in Atlanta, Georgia, USA in October 2018. Coverage is also provided for topics from the European Conference on Nonlinear Optical Spetroscopy (ECONOS 2018) held in April in Milan, Italy and GeoRaman 2018 in Catania, Italy in June. Finally, papers published in JRS in 2017 are highlighted and arranged by topics at the frontier of Raman spectroscopy. On the basis of this survey information, it is clear that Raman spectroscopy continues as in recent years as a rapidly expanding field of research across a wide range of novel disciplines and applications that provide sensitive photonic information of matter at the molecular level.