title: New Insights in 4f(12)5d(1) Excited States of Tm(2+) through Excited State Excitation Spectroscopy.
abstract: Optical excitation of ions or molecules typically leads to an expansion of the equilibrium bond lengths in the excited electronic state. However, for 4f(n-1)5d(1) excited states in lanthanide ions both expansion and contraction relative to the 4f(n) ground state have been reported, depending on the crystal field and nature of the 5d state. To probe the equilibrium distance offset between different 4f(n-1)5d(1) excited states, we report excited state excitation (ESE) spectra for Tm(2+) doped in CsCaBr3 and CsCaCl3 using two-color excited state excitation spectroscopy. The ESE spectra reveal sharp lines at low energies, confirming a similar distance offset for 4f(n-1)5d(t2g)(1) states. At higher energies, broader bands are observed, which indicate the presence of excited states with a different offset. On the basis of ab initio embedded-cluster calculations, the broad bands are assigned to two-photon d-d absorption from the excited state. In this work, we demonstrate that ESE is a powerful spectroscopic tool, giving access to information which cannot be obtained through regular one-photon spectroscopy.
authors.affiliation: Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University , Princetonplein 5, 3584 CC Utrecht, The Netherlands.
authors.forename: Mathijs
authors.initials: M
authors.lastname: de Jong
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern , 3012 Bern, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Biner
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern , 3012 Bern, Switzerland.
authors.forename: Karl W
authors.initials: KW
authors.lastname: Krämer
authors.affiliation: Departamento de Quı́mica, and Instituto Universitario de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid , 28049 Madrid, Spain.
authors.forename: Zoila
authors.initials: Z
authors.lastname: Barandiarán
authors.affiliation: Departamento de Quı́mica, and Instituto Universitario de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid , 28049 Madrid, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Seijo
authors.affiliation: Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University , Princetonplein 5, 3584 CC Utrecht, The Netherlands.
authors.forename: Andries
authors.initials: A
authors.lastname: Meijerink