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388 results on '"Lisiecki, Radosław"'

66. Size‐Dependent Photon Avalanching in Tm 3+ Doped LiYF 4 Nano, Micro, and Bulk Crystals

Author

Dudek, Magdalena, primary, Szalkowski, Marcin, additional, Misiak, Małgorzata, additional, Ćwierzona, Maciej, additional, Skripka, Artiom, additional, Korczak, Zuzanna, additional, Piątkowski, Dawid, additional, Woźniak, Piotr, additional, Lisiecki, Radosław, additional, Goldner, Philippe, additional, Maćkowski, Sebastian, additional, Chan, Emory M., additional, Schuck, P. James, additional, and Bednarkiewicz, Artur, additional

Published
2022
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78. Enhanced Emission of Tellurite Glass Doped with Pr 3+ /Ho 3+ and Their Applications.

Author

Burtan-Gwizdala, Bozena, Reben, Manuela, Cisowski, Jan, Lisiecki, Radosław, Jarząbek, Bożena, Alshehri, Ali, Hussein, Khalid I., and Yousef, El Sayed

Subjects
GLASS, RADIATION shielding, RADIATION protection, PHOTODYNAMIC therapy, ENERGY transfer, HOLMIUM
Abstract

The shielding and spectroscopic properties of Pr + 3 and Pr3+/Ho3+-codoped tellurite glass were investigated. The intensity parameters (Ω2 = 3.24-, Ω4 = 1.64-, Ω6 = 1.10 × 10−20 cm2) as well as the radiative lifetimes of 3F4 + 5S2 and 5I6 excited states of Ho3+ ions were equal to 301 μs and 3.0 μs, respectively. The former value appears to be much higher than that obtained from the lifetime measurement, indicating the presence of various energy transfer processes. The NIR spectrum of Pr3+/Ho3+-co-doped tellurite glass is dominated by strong Ho3+: 5I6 emission at around 1200 nm, being the result of the energy transfer from Pr3+ to Ho3+ ions. The shielding effectiveness of the prepared glasses showed good performance against high-energy photons. These findings suggest that the prepared glasses could be used in laser technology such as photodynamic therapy (PDT) treatment procedures and as shielding for radiation protection. [ABSTRACT FROM AUTHOR]

Published
2023
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84. Genthelvite and Willemite Examples

Author

Czaja, Maria, Lisiecki, Radosław, Juroszek, Rafał, and Krzykawski, Tomasz

Subjects
Mn2+, energy of excited level, crystal field parameters, luminescence
Abstract

The cause of the split of 4A4E(4G) Mn2+ excited level measured on minerals spectra is discussed. It is our view that ∆E = |4E(4G) − 4A(4G)| should be considered an important spectroscopic parameter. Among the possible reasons for the energy levels splitting taken under consideration, such as the covalent bond theory, the geometric deformation of the coordination polyhedron and the lattice site’s symmetry, the first one was found to be inappropriate. Two studied willemite samples showed that the impurities occur in one of the two available lattice sites differently in both crystals. Moreover, it was revealed that the calculated crystal field Dq parameter can indicate which of the two non-equivalent lattice sites positions in the willemite crystal structure was occupied by Mn2+. The above conclusions were confirmed by X-ray structure measurements. Significant differences were also noted in the Raman spectra of these willemites.

Published
2021
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93. Examining the Spectroscopic and Thermographic Qualities of Er 3+ -doped Oxyfluoride Germanotellurite Glasses.

Author

Ryba-Romanowski, Witold, Komar, Jarosław, and Lisiecki, Radosław

Subjects
ABSORPTION spectra, RADIATIVE transitions, MOLECULAR spectra, QUANTUM efficiency, BRANCHING ratios
Abstract

Novel ternary fluoro-germano-tellurite (GTS) glasses doped with Er3+ ions with 0.5 mol% and 1.0 mol% were fabricated by a conventional melt and quenching method and investigated using methods of optical spectroscopy. The room-temperature absorption spectrum was recorded and analyzed to determine radiative transition rates, radiative lifetimes, and branching ratios of Er3+ luminescence. Decay curves of Er3+ luminesccence were recorded and analyzed. Temperature dependences of emission spectra and absorption spectra in the region from RT (room-temperature) up to 675 K were studied in detail. The contribution of competing radiative and nonradiative processes to the relaxation of luminescent levels of Er3+ was assessed. Absolute and relative sensitivity were established utilizing the comprehensive model based on thermally coupled 2H11/2/4S3/2 excited states of erbium. The high quantum efficiency of the first erbium-excited state and value of gain coefficient indicate that GTS:Er glass system can be considered as conceivable NIR (near infrared) laser material as well. [ABSTRACT FROM AUTHOR]

Published
2022
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94. Size‐Dependent Photon Avalanching in Tm3+ Doped LiYF4 Nano, Micro, and Bulk Crystals.

Author

Dudek, Magdalena, Szalkowski, Marcin, Misiak, Małgorzata, Ćwierzona, Maciej, Skripka, Artiom, Korczak, Zuzanna, Piątkowski, Dawid, Woźniak, Piotr, Lisiecki, Radosław, Goldner, Philippe, Maćkowski, Sebastian, Chan, Emory M., Schuck, P. James, and Bednarkiewicz, Artur

Subjects
PHOTONS, HIGH resolution imaging, THULIUM ions, CRYSTALS, SINGLE crystals
Abstract

Photon avalanche (PA) is a highly nonlinear mode of upconversion that is characterized by 100–1000‐fold increase in luminescence intensity upon minute increments of pumping power. The practical realization of numerous possible nano‐bio‐technology applications utilizing the PA phenomenon will require information on its susceptibility to the material volume and surface. Here, these parameters are investigated via experimental and theoretical PA. The two‐color, highly nonlinear PA emission at 475 and 800 nm is clearly observed in bulk single crystal, individual microcrystals, and ensembles of colloidal core and core–shell nanoparticles of LiYF4 host doped with either 3 or 8% of thulium ions. The properties of PA emission, such as PA nonlinearity, PA gain, PA intensity, and luminescence kinetics in these materials show dependence on crystal volume and surface quenching. Theoretical simulations provide understanding of key physical processes that influence PA performance. Moreover, photon avalanche single beam super‐resolution imaging is realized for the first time in 3% Tm3+ doped LiYF4 core–shell nanoparticles. The obtained insights and predictions form a solid background for further development and applications of new optimized PA materials. [ABSTRACT FROM AUTHOR]

Published
2022
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