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High pressure energy-dispersive X-ray absorption spectroscopy is a valuable structural technique, especially, when combined with a nano-polycrystalline diamond anvil cell. Here we present recent results obtained using the dispersive setup of the ODE beamline at SOLEIL synchrotron. The effect of pressure and temperature on the X-ray induced photoreduction is discussed on the example of nanocrystalline CuO. The possibility to follow local environment changes during pressure-induced phase transitions is demonstrated for α-MoO 3 based on the reverse Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

This work investigates the Mn2+ electronic structure and photoluminescence (PL) in [(CH3)4N]2MnCl4 and [(CH3)4N]2MnBr4 and their variation with pressure by time-resolved excitation and emission spectra in the 0-10 GPa range. We show that both the crystal-field excitation and corresponding PL bands experience large-pressure redshifts (about 5 nm/GPa), which are associated with the high crystal compressibility and the interaction between organic/inorganic ([CH3]4N-/MnX[image omitted] ) tetrahedra. The energy variation as a function of pressure is explained in terms of the isolated Td MnX[image omitted] in the respective crystals through crystal-field models. One salient feature is the reduction of the PL Stokes shift with pressure in both crystals as-1.0 and-1.7 nm/GPa for chloride and bromide, respectively. [ABSTRACT FROM AUTHOR]

This work investigates the Co2+(Td) electronic structure and photoluminescence (PL) in MgAl2O4:Co2+ and their variation with pressure by time-resolved spectroscopy. The absorption spectra and the pressure and temperature dependences of the emission band at 663 nm (τ=120 ns, at ambient conditions) can be explained on the basis of a configurational energy model, which provides an interpretation of the electronic structure and the excited-state phenomena. We show that there is an excited-state crossover [4T 1(P)↔2E (G)] at ambient pressure, which is responsible for the evolution of the emission spectrum from a broadband emission between 300 and 100 K to a narrow-peak emission at 6 K. The pressure, instead of enhancing excited-state crossover phenomena, reduces PL and suppresses it (PL quenching) above 6 GPa. We explain such variations in terms of pressure-induced non-radiative crossover relaxation to lower excited states: 2E (G)→4T 1(F). The variation of PL intensity and its associated lifetime with pressure supports the proposed interpretation. [ABSTRACT FROM AUTHOR]