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161 results on '"Aceves, R."'

15. Europium luminescence enhancement induced by a resonant mode in a waveguide of planar metallic walls.

Author

Ramírez-Duverger, Aldo S., Aceves, R., García-Llamas, Raúl, and Gaspar-Armenta, Jorge A.

Subjects
*EUROPIUM, *LUMINESCENCE, *PHOTONICS research, *DOPED semiconductors, *WAVE-guide circulators, *ALUMINUM, *MAGNESIUM fluoride, *THIN film research, *OPTICS, *EQUIPMENT & supplies
Abstract

We report the experimental results of emission from europium ions inside a planar waveguide. The waveguide is constituted by a MgF2:Eu2+ film between Al metallic walls, with a film thickness appropriate to support a guided mode with wavelength inside of the excitation spectrum of the Eu ions. A guided mode is produced by incident light through a thin metallic film at an angle of incidence such that its wave vector component parallel to the waveguide couples resonantly to the mode. The luminescence of Eu2+ in the waveguide of polycrystalline MgF2 was found to have a maximum at 440 nm. This emission was ascribed to electronic transitions of Eu2+ ions dipoles on a lattice of MgF2. For an excitation light of 360 nm, the integrated emission versus angle of incidence showed a maximum for an incident light angle of 20°. This behavior is explained because of the excitation light, for those wavelength and angle of incidence, couple to a mode along the waveguide and more emitters are excited in the optical path of the guided light. [ABSTRACT FROM AUTHOR]

Published
2010
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21. Cathodoluminescence in europium doped KCl crystals

Author

Aceves, R., Perez Sala, R., Barboza Flores, M., Pal, U, Zaldivar, M.H., Piqueras de Noriega, Javier, Aceves, R., Perez Sala, R., Barboza Flores, M., Pal, U, Zaldivar, M.H., and Piqueras de Noriega, Javier

Abstract

© Taylor & francis Ltd. International Conference on Defects in Insulating Materials (2000. Johannesburg, Sudáfrica), Spectral cathodoluminescence of KCl:EU2+ (0.2% wt) crystals has been measured at different temperatures. In the 80-300 K temperature range the luminescence consists of three main broad emission bands with maxima around 418, 452, and 619nm. Based on photoluminescence studies the 418nm could be associated with the 4f(6)5d (t(2g))-4f(7) (S-8(7/2)) radiative transition of the Eu2+ ions in the KCl matrix. The band with maximum at 452 nm could be associated with the alpha-center emission as in pure KCl. The 619 nm band has been considered as a part of the luminescence modified by the absorption of the F centers formed during irradiation. The intensity of all these bands versus temperature shows a minimum around 150 K, an indication of a low defect mobility produced with the electron-beam irradiation., Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Published
2001

28. RES structure of Bi3+ centres in KCl:Bi,S and CaO:Bi crystals.

Author

Aceves, R., Flores, M. B., Maaroos, A., Nagirnyi, V., Salas, R. P., Tsuboi, T., Zazubovich, S., Zepelin, Viktor, Aceves, R., Flores, M. B., Maaroos, A., Nagirnyi, V., Salas, R. P., Tsuboi, T., Zazubovich, S., and Zepelin, Viktor

Abstract

Emission, excitation, and polarization spectra as well as decay kinetics are studied at 4.2 to 500 K for the luminescence of Bi3+ centres in two crystals (KCl and CaO) with strongly different electron-phonon interaction. It is concluded that three bands at approximate to 2.5, 3.11, and approximate to 1.5 eV, observed in the emission spectrum of the kCl:Bi, S crystal belong to the same centre, but arise from states of different origin; The splitting of the 2.5 eV band, caused by the presence of a defect (S2-) near a Bi3+ ion is detected. Besides the well-known tripler 3.3 and 3.1 eV bands, a new 4.15 eV emission is found in CaO:Bi crystal: which is ascribed to transitions from the singlet excited state of the Bi3+ ion. The structure and the parameters of the relaxed excited states are determined and the models of the corresponding Bi3+ centres are discussed.

Published
1996

32. Spectroscopy of CsPbBr3 quantum dots in CsBr:Pb crystals

Author

Aceves, R., primary, Babin, V., additional, Flores, M.Barboza, additional, Fabeni, P., additional, Maaroos, A., additional, Nikl, M., additional, Nitsch, K., additional, Pazzi, G.P., additional, Salas, R.Perez, additional, Sildos, I., additional, Zazubovich, N., additional, and Zazubovich, S., additional

Published
2001
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35. Luminescent characteristic of the CsBr phosphor activated with Eu2+ and Mn2+ ions.

Author

Téllez-Flores, E., Aceves, R., Pérez-Salas, R., Camarillo, I., and Caldiño, U.

Subjects
*CESIUM compounds, *PHOTOLUMINESCENCE, *BROMIDES, *PHOSPHORS, *MANGANESE compounds, *CRYSTALLIZATION
Abstract

Abstract: Spectra of excitation and emission were measured at RT and 15K in crystals quenched (Q) of CsBr:Eu2+, CsBr:Mn2+ and CsBr:Eu2+,Mn2+. Emission bands at 444, 480, 520 and 570nm with different relative intensities are generated in the samples after UV excitation. The blue band at 444nm was ascribed with unknown clusters or aggregated centers (AC) of dipoles type Eu2+–VC − and insulated dipole centers (IDC) like Eu2+–O2−. The bands at 480, 520 and 570nm were assigned to Cs4EuBr6 nanocrystals; AC containing units in tetrahedral symmetry and another yet unidentified AC defect, respectively. In crystals of CsBr:Eu2+,Mn2+ the excitation and emission spectra taken at 15K show no clear evidence of an energy transfer mechanism. Instead, the results suggest that the emission is produced by direct excitation of the ions of Eu2+ and Mn2+. Accordingly, single- or double-doped CsBr crystals may contain the same type of defects, either AC and/or IDC. [Copyright &y& Elsevier]

Published
2013
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42. Quantum size effect in the excitonic luminescence of CsPbX3-like quantum dots in CsX (X = Cl, Br) single crystal host

Author

Nikl, M., primary, Nitsch, K., additional, Polák, K., additional, Mihókova, E., additional, Zazubovich, S., additional, Pazzi, G.P., additional, Fabeni, P., additional, Salvini, L., additional, Aceves, R., additional, Barbosa-Flores, M., additional, Salas, R.Perez, additional, Gurioli, M., additional, and Scacco, A., additional

Published
1997
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