Optical properties of Eu3+ ions in malonate crystals to monitor a structural phase transition

Abstract Laser-excited site-selective spectroscopy on Eu3+ ions has been used in malonate crystals to detect a structural phase transition. From room temperature to about 240 K, a unique local site for the Eu3+ ions is observed. However, two different sites are clearly identified below this temperature evidencing a structural phase transition. Moreover, site-selective and time-resolved spectroscopies have been used to prove that an energy transfer process between these two sites exists for the low temperature phase. The decay of the luminescence of the Eu3+ ions in both sites has been studied after resonant excitation of the Eu3+ ions in one of them. The solution of the proposed rate equations has been used to obtain the temperature dependence of the energy transfer probability.