FinEstBeAMS (Finnish–Estonian Beamline for Atmospheric and Materials Sciences) is a multidisciplinary beamline constructed at the 1.5 GeV storage ring of the MAX IV synchrotron facility in Lund, Sweden. The beamline covers an extremely wide photon energy range, 4.5–1300 eV, by utilizing a single elliptically polarizing undulator as a radiation source and a single grazing-incidence plane grating monochromator to disperse the radiation. At photon energies below 70 eV the beamline operation relies on the use of optical and thin-film filters to remove higher-order components from the monochromated radiation. This paper discusses the performance of the beamline, examining such characteristics as the quality of the gratings, photon energy calibration, photon energy resolution, available photon flux, polarization quality and focal spot size.

The luminescence properties of Sc_xY_1−xPO₄:Eu³⁺ solid solutions have been studied under excitation by synchrotron radiation in the energy range of 4.5–50 eV. The luminescence originating from three different types of emission centers was observed, and the origin of the emission centers was determined. The light output of Sc_xY_1−xPO₄:Eu³⁺ was shown to depend non-linearly on the ratio of Sc and Y cations, whereas it is maximal in compounds with their equal content. The branching of the energy relaxation process between different emission centers is analyzed for the brightest Sc_0.5Y_0.5PO₄:Eu³⁺ solid solution.

Lanthanide ions exhibit characteristic emission originating from intra- 4 f transitions. Among them, hypersensitive transitions (HSTs) are distinguished by their pronounced spectral tunability. Conventional HST emitters typically rely on dilute doping and host-to- 4 f charge transfer, which are often limited by defect-induced quenching and transfer losses. Here, we observe a highly efficient HST channel independent of a host-to- 4 f transfer in undoped, intrinsically luminescent europium-based double perovskites, and we identify the mechanisms that govern both the enhancement and loss of HST efficiency. In this system, a thermally activated doubly degenerate phonon mode of the Eu − Cl 6 octahedra relaxes the parity selection rule, thereby strengthening the HST emission. The HST oscillator strength is enhanced by a factor of 2–3 relative to that of the magnetic-dipole transition. Direct excitation into the L J 5 level bypasses reverse energy transfer and yields a maximum quantum efficiency of nearly 70%. These findings provide insights into the design of efficient and spectrally tunable emission in lanthanide systems.

The photoluminescence (PL) and photoluminescence excitation (PLE) spectra of an EFG-grown (−201) β-Ga₂O₃ single crystal were recorded at 7 and 300 K at the FinEstBeAMS beamline of the MAX IV Laboratory. Excitation–emission maps and fixed-wavelength PLE profiles covered 4.50–10.50 eV at both temperatures. Each temperature series was normalized to its own 5.00 eV intensity and, alternatively, to its own maximum; the reported ratios therefore describe excitation dependence within one series and not an absolute difference in luminescence yield between temperatures. At 7 K, integrated emission at 10.50 eV retains 95.4% of its 5.00 eV value and 89.2% of its maximum. At 300 K, the PLE half-height is 4.55 eV, and the maximum occurs at 4.75–4.80 eV, followed by a decrease to 2.26% of the 5.00 eV value and 2.03% of the maximum at 10.50 eV. Room-temperature ellipsometry on the same factory-polished face places the PLE rise in the rapidly increasing absorption region and yields a penetration depth of approximately 0.24 μm near the PLE half-height and 37 nm at 5.90 eV. A constrained depth-dependent calculation does not reproduce the full decline, so surface capture is retained as one possible pathway rather than an established mechanism. The emission is described by the same effective bands at 3.55, 3.37 and 3.07 eV used in the preceding laser study. Their balance is nearly constant at 7 K, whereas the low-energy spectral weight increases at 300 K under deep-VUV excitation. These spectra provide quantitative reference profiles for energy conversion and carrier capture in β-Ga₂O₃.

The intrinsic defect-related luminescence of as-grown Gd₃Ga₅O₁₂ (GGG) single crystals was investigated using synchrotron excitation in the vacuum-ultraviolet region. The photoluminescence spectrum at 7 K exhibits a broad emission band centered near ~2.5 eV (≈500 nm), accompanied by narrow 4f–4f transitions of uncontrolled Tb³⁺ impurity ions. Gaussian decomposition of the broad band reveals three components at approximately 3.05, 2.70, and 2.50 eV, attributed to self-trapped excitons (STE), antisite-associated recombination, and F/F⁺-type oxygen-vacancy centers, respectively. Temperature-dependent photoluminescence measurements show that the defect-related luminescence is governed by two thermally activated nonradiative channels with activation energies of ~5–8 meV and 42–56 meV. The shallow channel dominates at 20–50 K, while the main quenching occurs between 100 and 150 K, leading to nearly complete suppression of the broad emission at room temperature. The present results therefore characterize the emission behavior of intrinsic, shallow defect centers in as-grown GGG and contribute to understanding defect recombination pathways that are critical for optimizing garnet-based scintillation and photonic materials.