9-13 July 2012
Africa/Johannesburg timezone
<a href="http://events.saip.org.za/internalPage.py?pageId=11&confId=14"><font color=#ff0000>SAIP2012 PROCEEDINGS AVAILABLE</font></a>

Interaction mechanism for energy transfer from Ce to Tb ions in silica

11 Jul 2012, 17:10
Oral Presentation Track A - Division for Condensed Matter Physics and Materials DCMPM2


Mr Hassan Seed Ahmed (University of the Free State)

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Abstract content <br> &nbsp; (Max 300 words)

Energy transfer phenomena can play an important role in the development of luminescence materials. For example, the green luminescence from Tb3+ doped silica can only be excited efficiently using very short wavelength UV light near 227 nm. However, the excitation wavelength can be shifted to a more accessible value of 325 nm by co-doping with Ce3+ ions which absorb at this wavelength and then transfer the energy to the Tb3+ ions. Inokuti and Hirayama developed models for radiationless energy transfer that occurs via the exchange interaction or various types of multipole interactions. In this work numerical simulations based on these theoretical models are compared to experimental results obtained for the energy transfer from Ce to Tb in sol-gel silica. The experimental results were obtained by exciting samples with a fixed concentration of Ce (the donor) and varying the concentration of Tb (the acceptor). Energy transfer from the donor to the acceptor results in a decrease in the donor (Ce) luminescence intensity and lifetime. It was found that the decrease in the donor intensity corresponded well with the energy transfer models based on the exchange and dipole-dipole interaction. The critical transfer distance obtained from the fitting using both models is around 20 angstrom suggesting that the dipole-dipole interaction is more appropriate than the exchange interaction which requires a distance shorter than 10 angstrom to occur. Although the donor decay lifetime data has the same trend as the corresponding theoretical curve, it does not decrease as much as expected. The decay curves from pure Ce-doped silica are not simple exponential decays as expected. This indicates that Ce ions may occur in different environments in the amorphous silica hosts, and these have different lifetimes, complicating the analysis of the lifetime data.

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Main supervisor (name and email)<br>and his / her institution

R.E. Kroon, kroonRE@ufs.ac.za, University of the Free State

Primary authors

Mr Hassan Seed Ahmed (University of the Free State) Prof. O.M. Ntwaeaborwa (University of the Free State) Dr R.E. Kroon (University of the Free State) Dr W.-S. Chae (3Korea Basic Science Institute (KBSI))

Presentation Materials