Inorganic and Solid State Chemistry, Saarland University, P.O. Box 151150, 66041 Saarbrücken, Germany.
Phys Chem Chem Phys. 2014 Mar 14;16(10):4807-13. doi: 10.1039/c3cp55102d.
The luminescence of Eu(2+) in hydride and deuteride perovskite hosts LiMH3 and LiMD3 (M = Sr, Ba) is reported. Bright yellow (M = Sr) and green (M = Ba) emission is observed and assigned to 4f(6)5d-4f(7) emission from Eu(2+) in the highly symmetric 12-coordinated M(2+) site (m3[combining macron]m). The long wavelength of the emission is explained by the strong covalence and crystal field splitting in europium's coordination by hydride anions. A well-resolved vibrational structure in the emission and excitation spectra of Eu(2+) in the Sr-compounds allows for an accurate determination of the energy of the lowest 4f(6)5d state and vibrational frequencies, for both the hydride and deuteride. The isotope effect on the energy of the fd states is small (∼70 cm(-1)), as expected. Surprisingly, also the vibrational energies observed in the vibronic progression are similar for the d-f emission spectra in LiSrH3 and LiSrD3. This is explained by strong coupling of the d-f emission with low energy acoustic phonons which, contrary to optical phonons, are not strongly affected by replacing H by D. The present results provide insight into the long wavelength Eu(2+) emission in hydride coordination and the influence of isotope replacement on the luminescence.
Eu(2+)在氢化物和氘化物钙钛矿宿主 LiMH3 和 LiMD3（M = Sr，Ba）中的发光被报道。观察到明亮的黄色（M = Sr）和绿色（M = Ba）发射，并将其归因于 Eu(2+)在高度对称的 12 配位 M(2+)位（m3[combining macron]m）中 4f(6)5d-4f(7)发射。发射的长波长解释为氢化物阴离子对 Eu(2+)配位的强烈共价性和晶体场分裂。Eu(2+)在 Sr 化合物中的发射和激发光谱中存在良好分辨的振动结构，允许准确确定最低 4f(6)5d 态的能量和振动频率，对于氢化物和氘化物都是如此。对 fd 态能量的同位素效应较小（约 70 cm(-1)），这是预期的。令人惊讶的是，LiSrH3 和 LiSrD3 中 d-f 发射光谱的振动态序中观察到的振动能也相似。这是通过 d-f 发射与低能声学声子的强耦合来解释的，与光学声子不同，它们不受用 D 取代 H 的强烈影响。本研究结果提供了对氢化物配位中 Eu(2+)长波长发射以及同位素取代对发光的影响的深入了解。
