title: Modeling blue to UV upconversion in β-NaYF4:Tm3.
abstract: Samples of 0.01% and 0.3% Tm3+-doped β-NaYF4show upconverted UV luminescence at 27 660 cm-1(361 nm) after blue excitation at 21 140 cm-1(473 nm). Contradictory upconversion mechanisms in the literature are reviewed and two of them are investigated in detail. Their agreement with emission and two-color excitation experiments is examined and compared. Decay curves are analyzed using the Inokuti-Hirayama model, an average rate equation model, and a microscopic rate equation model that includes the correct extent of energy transfer. Energy migration is found to be negligible in these samples, and hence the average rate equation model fails to correctly describe the decay curves. The microscopic rate equation model accurately fits the experimental data and reveals the strength and multipolarity of various interactions. This microscopic model is able to determine the most likely upconversion mechanism.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland. pedro.villanueva@dcb.unibe.ch.
authors.forename: Pedro
authors.identifier: http://orcid.org/0000-0002-1672-9432
authors.initials: P
authors.lastname: Villanueva-Delgado
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland. pedro.villanueva@dcb.unibe.ch.
authors.forename: Karl W
authors.initials: KW
authors.lastname: Krämer
authors.affiliation: Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Cantabria-IDIVAL, 39005 Santander, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Valiente
authors.affiliation: Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands.
authors.forename: Mathijs
authors.initials: M
authors.lastname: de Jong
authors.affiliation: Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, 3508TA Utrecht, The Netherlands.
authors.forename: Andries
authors.initials: A
authors.lastname: Meijerink