Dr. Sebastian Vielhauer Profile

Dr. Sebastian Vielhauer

at Univ of Tartu

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Publications (4)

Proceedings Article | 19 May 2011 Paper

Relaxation and interaction of electronic excitations induced by intense ultra short light pulses in BaF[sub]2[/sub] scintillator

M. Kirm, V. Nagirnyi, S. Vielhauer, E. Feldbach

Proceedings Volume 8077, 80770U (2011) https://doi.org/10.1117/12.887601

KEYWORDS: Luminescence, Free electron lasers, Excitons, Solar thermal energy, Crystals, Absorption, Laser crystals, Vacuum ultraviolet, Scintillators, Ultraviolet radiation

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Excitation density effects have a pronounced influence on relaxation processes in solids. They come into play in scintillating and dosimetric materials exposed to ionizing radiation or in laser materials operating in intense ultraviolet light fields. The scientific understanding of the underlying process is poor, mainly because most of the studies of light emitting materials under short wavelength excitation have been performed at weak and moderate excitation intensities due to limited availability of powerful light sources. Disembodied data on excitation density effects have been reported for wide-gap dielectrics studied by luminescence spectroscopy, by using such excitation sources as powerful ion beams,^1,2pulsed electron beams,^2,3 and wide-band hard X-ray synchrotron radiation.4 It is obvious that such non-selective excitation is a good tool for revealing density-related phenomena in these materials in general, but for investigating specific features of relaxation processes in insulators, light sources with well defined parameters are necessary. Since the shortwavelength free electron laser (FEL) technology has been devised by an international consortium at HASYLAB of DESY, resulting in the development of TESLA Test facility (TTF)5 and later in the construction of a dedicated FEL source FLASH in Hamburg,6 more advanced studies became possible. The range of interests towards this light source covers the fields from material science and various other branches of physics to structural biology. The pioneering luminescence study revealed excitation density effects in the decay of Ce³⁺ 5d-4f luminescence in Y3Al5O12 crystals and luminescence of BaF2 crystals in UV-visible range.7 These results motivated systematic investigations of excitation density effects in wide gap crystals using FEL8,9 and high-harmonic-generated VUV radiation,10 and, at lower energies, femtosecond laser pulses in the UV.^11,12The main goal of the present work is to analyze the same phenomenon in wide-band gap BaF2 crystals, where luminescence centres of different origin (self-trapped excitons and cross-luminescence) are present. Using models developed for explaining the non-linear behaviour of luminescence and exciton-exciton interaction effects causing scintillator non-proportionalities,^10,13 simulations of luminescence decay curves are performed. Possible quenching effects in the cross-luminescence decay of BaF2 under XUV excitation have been analyzed by Terekhin et al.¹⁴

Proceedings Article | 18 May 2009 Paper

Phosphor materials under high-density XUV FEL excitation: mechanisms of luminescence quenching

Sebastian Vielhauer, Vladimir Babin, Marco De Grazia, Eduard Feldbach, Marco Kirm, Vitali Nagirnyi, Andrej Vasil'ev

Proceedings Volume 7361, 73610R (2009) https://doi.org/10.1117/12.822292

KEYWORDS: Free electron lasers, Luminescence, Photons, Solar thermal energy, Ions, Crystals, Extreme ultraviolet, Scintillators, Excitons, Absorption

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Proceedings Article | 15 June 2007 Paper

Applications of intense ultra-short XUV pulses to solid state physics: time resolved luminescence spectroscopy and radiation damage studies

M. De Grazia, H. Merdji, B. Carré, J. Gaudin, G. Geoffroy, S. Guizard, N. Fedorov, A. Belsky, P. Martin, M. Kirm, V. Babin, E. Feldbach, S. Vielhauer, V. Nagirnyi, A. Vassil'ev, F. Krejci, J. Kuba, J. Chalupsky, J. Cihelka, V. Hajkova, M. Ledinský, L. Juha

Proceedings Volume 6586, 65860I (2007) https://doi.org/10.1117/12.724006

KEYWORDS: Extreme ultraviolet, Luminescence, Polymers, Polymethylmethacrylate, Excitons, Solar thermal energy, Crystals, Solids, Raman spectroscopy, Time resolved spectroscopy

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Proceedings Article | 12 June 2006 Paper

VUV luminescence of as-grown and electron irradiated corundum single crystals

Marco Kirm, Vachagan Harutunyan, Vladimir Makhov, Sebastian Vielhauer

Proceedings Volume 5946, 594606 (2006) https://doi.org/10.1117/12.639064

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