Abstracts 2001

Abstract of Publication No. 409

G. M. Salley, R. Valiente and H. U. Güdel
Luminescence upconversion mechanisms in Yb3+-Tb3+ systems
J. Lumin. 94-95, 305-309 (2001)      Full Text (PDF)      DOI-Link     

Abstract: Tb3+ (5D4 7FJ) luminescence has been observed in single crystals of SrCl2: Tb3+ (1%): Yb3+ (1%) and Cs3Tb2Br9: Yb3+ (1%) under excitation energies in the region of Yb3+ absorption. Previous reports of similar systems have postulated two possible upconversion mechanisms: (1) cooperative sensitization and (2) a sequence of two cooperative absorption steps, or GSA/ESA. We present results of emission, excitation and kinetic measurements at low and high temperatures. These measurements allow assignment of the mechanism responsible for upconversion in these systems. For temperatures greater than T = 100 K process (1) is the dominant mechanism, in agreement with previous assignments. However, for T < 100 K in Cs3Tb2Br9: Yb3+ (1%), the upconversion occurs through a GSA/ESA sequence, which is shown here in a clear manner for the first time. The efficiency of the Yb3+-Tb3+ upconversion process for SrCl2: Tb3+ (1%): Yb3+ (1%), at room temperature, under 2.4(10)4 W/cm2, is on the order of 104 and decreases with decreasing temperature by four orders of magnitude.

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