FTIR Spectral Dataset of E-type Diamonds collected at the Diamond Light Source Synchrotron

This dataset contains a collection of micro-Fourier transform infrared spectroscopy (micro-FTIR) spectra acquired during a beamtime session at the Diamond Light Source synchrotron facility. The dataset includes spectra collected from four lithospheric eclogitic diamonds from the Udachnaya kimberlite pipe, located in the Daldyn-Alakit kimberlite field, Yakutia Province, Siberian Craton. The analysed samples are DIA4, DIA5, LGM12, and LGM15. All samples originally exhibited an octahedral morphology and contained mineral inclusions that were visible and distinguishable under a stereomicroscope. Micro-FTIR data were collected in transmission mode at the MIRIAM beamline B22 of the Diamond Light Source facility, UK, using a Bruker Hyperion 3000 IR microscope coupled to a Vertex 80V FTIR spectrometer. A 36× objective and equivalent condenser optics were used, together with a knife-edge aperture positioned in the detection beam path and a high-sensitivity liquid-nitrogen-cooled MCT detector with a 50 µm pitch. Background measurements were acquired on the underlying BaF2 plate using 512 scans per analysis. Spectra were collected over the wavenumber range 4000–500 cm-1, with a spectral resolution of 2 cm-1 and 256 scans per spectrum, corresponding to approximately 1 minute per point to ensure optimal spectral quality. High-resolution FTIR maps covering areas of approximately 100 × 100 µm2 were acquired using a 10 × 10 µm2 knife-edge aperture and a 7 µm stage step size, resulting in a 3 µm point overlap. In addition, line-scan transects consisting of 30 analytical spots were acquired using a 10 × 10 µm2 aperture and a 10 µm step size. These transects were used to survey diamond surfaces and evaluate spatial variability in N- and H-related infrared features in proximity to, and at, mineral inclusions. Spectral acquisition and visualization were performed using Bruker OPUS v8.7.41. Spectra showing saturation effects, interference from mineral inclusions, or surface-related irregularities were excluded from the final dataset. Additional information on sample description, analytical procedures, data treatment, and scientific interpretation will be provided in the associated publication Angellotti et al. (2025) and a dedicated manuscript related to this dataset, once the peer-review process has been completed. Restricted repository access will be lifted as soon as the dedicated manuscript is published online.