THERMAL DEPENDENCE OF MN2+ AND ND3+ FLUORESCENCE AND OF MN2+-]ND3+ ENERGY TRANSFER IN RBMNF3

We have measured the absorption, excitation, and fluorescence spectra and lifetimes of Mn2+ and Nd3+ in RbMnF3 in the 15-300A°K region. The fluorescence spectrum of Mn2+ in this system presents a wide band which, going up in temperature, shows a sharp decrease in intensity and shifts its maximum from 5820 to 6300 ãat ∼32A°K. The Nd3+ emission consists of two groups of sharp lines centered at ∼10 600 and 8900 ã and corresponding to the transitions F324→I1124 and F324→I924, respectively; also, going up in temperature the intensity of the Nd3+ fluorescence increases sharply at ∼32A°K. The excitation spectra of Nd3+ reveal the presence of Mn2+ → Nd3+ energy transfer even at room temperature, where the Mn2+ fluorescence is completely quenched. The thermal variation of the Nd3+ fluorescence is opposite to that expected on the basis of the change in the overlapping of the Mn2+ fluorescence and Nd3+ absorption bands; this fact, together with the observed Mn2+ → Nd3+ energy transfer in the absence of the Mn2+ fluorescence, imply that the dominant energy-transfer mechanism is of a nonradiative type. The decay pattern of the Mn2+ fluorescence response in RbMnF3 reveals a different behavior at ∼5820 and ∼6300 ã, implying the existence of two real metastable levels for Mn2+. Information on the kinetics of the Mn2+ fluorescence and of the Mn2+ → Nd3+ energy transfer is also derived from lifetime measurements. © 1969 The American Physical Society.