ATR-FTIR spectral database of geological, experimental, and archaeological materials

Description

Methods

A table linked to the database summarised the information available for the samples.
The composition of each sample was verified by the authors according to FTIR-ATR spectra and data available in the literature. 
If samples have already been published, the article references have been included in the database. 
In cases of uncertainty regarding the composition of minerals, X-ray diffraction analyses were performed and the results of which are associated with the FTIR spectra.
All samples for which the composition was doubtful were removed from the database.

FTIR-ATR spectral data were acquired between 2005 and 2024. After 2014, FTIR-ATR spectra were collected on a Vertex 70 spectrometer (Bruker) equipped with an external water cooled globar source, an ultra-wide range beamsplitter, and a wide-range diamond window DLaTGS detector. This system allows recording of the spectral range from 6000 cm-1 to 50 cm-1 in a single step (Bruker far- and mid-IR technology). Less than 0.5 mg of sample powder was pressed onto the surface of the crystal using a single reflection diamond ATR accessory (Extended Range Diamond Quest accessory, Specac). According to the signal-to-noise ratio, decreasing in FIR range under 150 cm-1, ATR-spectra were acquired with a spectral resolution of 4 cm-1 and the accumulation of 128 scans in the range of 6000–80 cm-1. Prior to 2014, FTIR-ATR spectra were collected on a Vector 22 spectrometer (Bruker) equipped with a globar source, a KBr beamsplitter, and a DLaTGS detector. These spectra were collected using a golden gate diamond ATR accessory (Specac) over the 4000–400cm-1 range. Depending on the application and the user, the spectra were acquired under different conditions: the spectral resolution varied from 2 to 4 cm-1 and the accumulation from 16 to 64 scans. When possible, samples acquired on Vector22 spectrometer before 2014 were re-analysed on the Vertex 70 system in order. The acquisition conditions are reported in the information table. All analyses were performed at the "Plateau de Spectrométrie Infrarouge" at the Muséum National d'Histoire Naturelle (Paris).
The signal to noise ratio increases below 150 cm-1. Spectra range below 100 cm-1 should be interpreted with great caution.
FTIR-ATR are provided as Bruker OPUS file (.0) and JCAM-DX (Robert S. McDonald and Paul A. Wilks, "JCAMP-DX: A Standard Form for Exchange of Infrared Spectra in Computer Readable Form," Appl. Spectrosc. 42, 151-162 (1988) 
The Bruker OPUS file and JCAM-DX can be read by various software, including spectragryph developed by Dr Friedrich Menges (https://www.effemm2.de/index.html ; free license for individual users for non-commercial, private, academic and educational use).

The composition of the geological sample from the MNHN collections was verified by X-ray diffraction after grinding of a few mg. X-ray diffraction was carried out on a silicon zero diffraction plate using a D2 phaser diffractometer (Bruker) equipped with Cu-ka anode (λ = 0.15406 Å) operating at 30 kV and 10 mA. Diffractograms were collected from 3° to 65° 2 teta angles with a step increment of 0.04° and a counting time of 0.2s per step. Diffractograms were treated using DiffracEva software (Bruker) and the identification of mineral components was achieved using the PDF2 database.
XRD data are provided as .xy. files which can be read and processed using Open Source Profex software (https://www.profex-xrd.org/), or converted to various formats using PowDLL Converter software ( http://users.uoi.gr/nkourkou/powdll/ ; PowDLL is free for academic or commercial use).

Other

Acknowledgments:

We would like to warmly thank the many contributors to this database, starting with the technicians, engineers and researchers who have worked on the « Plateau de spectroscopie Infrarouge du MNHN » over the past 15 years, specifically Anne-Marie Brunet, Mehdi Dionigi, Axel Ledoze, Maeva Lafitte, Margot Guernalec, Anta Sow and Lisa Garbé. We would like to thank Marie-Madeleine Blanc-Valleron for access to the XRD diffractometer and help analyzing the minerals. We are grateful to the former students and PhD students who contributed to this spectral database, specifically Sandra Ventalon, Melody Stein, Sonia Ostaptchouk, Gala Gomez-Merino, Omar Choa, Gregorio Dal Sasso, and Patrick Schmidt. We thank the  "Plateforme analytique du Muséum national d’Histoire naturelle" for their financial support of the  "Plateau de Spectrométrie Infrarouge du MNHN". We are also grateful to the "Collections de Mineralogie du Muséum national d’Histoire Naturelle" for providing mineralogical references and especially Cristiano Ferraris for the sample selection.