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1

Digitale Medien

Optical design considerations and performance of a spectro-streak apparatus for time-resolved fluorescence spectroscopy (1993)

Wiessner, A. ; Staerk, H.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 64 (1993), S. 3430-3439

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: A time-resolved spectral photometer, i.e., an instrument for simultaneously measuring intensity, time, and wavelength (I-t-λ) is described. The "spectro-streak'' apparatus comprises a grating objective coupled to a commercial streak camera with 2-ps resolution, a channel plate amplifier, a CCD camera, and a computer for data processing. The necessary calibration and correction procedures are discussed in detail; these are sweep nonlinearity correction, shading correction, geometric distortion correction, wavelength calibration, spectral intensity correction, and dispersion correction. The performance of the instrument is demonstrated with an example of current interest, the measurement of the solvatochromic dynamic Stokes shift of fluorescence from a charge-transfer system in solution.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1144264

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2

Digitale Medien

Design considerations and performance of a combined scanning tunneling and scanning electron microscope (1997)

Wiessner, A. ; Kirschner, J.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 68 (1997), S. 3790-3798

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: We designed and built a combination of a scanning tunneling microscope (STM) and a scanning electron microscope (SEM) which is working under ultrahigh vacuum conditions (base pressure typically 7⋅10−11 mbar). The SEM is ideally used for surveying the sample and to control the STM tip positioning, while the STM extends the resolution range into the atomic scale. The design concept allows moving the STM tip freely over the sample under SEM control and using both imaging techniques simultaneously. The system is equipped with an electron energy analyzer (cylindrical sector analyzer) providing Auger electron spectroscopy, scanning Auger microscopy (SAM) and x-ray photoelectron spectroscopy capabilities. In addition, low energy electron diffraction and reflection high energy electron diffraction facilities are installed. In order to use these very different imaging techniques in situ, several special solutions had to be incorporated in the design of the system; they are described in detail. Some results are presented which demonstrate the performance of the STM/SEM system. Atomic resolution of the STM, a SEM resolution of up to 20 nm, and a SAM resolution of better than 100 nm were achieved. © 1997 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1148028

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3

Digitale Medien

Design considerations and performance of a spectro-streak apparatus applying a planar LIGA microspectrometer for time-resolved ultrafast fluorescence spectroscopy (1996)

Staerk, H. ; Wiessner, A. ; Müller, C. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 67 (1996), S. 2490-2495

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: Results of a pilot study with a spectro-streak apparatus applying a grating microspectrometer with a self-focusing reflection grating are reported. The microspectrometer chip (dimensions: 17×6.4 mm2; 125 μm effective thickness of the three-layer x-ray resist system), fabricated with the versatile LIGA technique, has been adapted to a picosecond streak camera. Performance tests have been carried out with a fluorescent probe exhibiting a dynamic Stokes shift of the exciplex fluorescence band due to solvation of the charge transfer dipole within about 400 ps. The use of a LIGA microspectrometer in ultrafast spectroscopy proved to be of advantage in time-resolved studies of complex luminescence spectra where a moderate spectral resolution is required and a large spectral range must be covered. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1147203

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4

Digitale Medien

Electron Transfer, Solvation, and Amplified Stimulated Emission of Pyrene-DMA and Anthracene-DMA (1995)

Wiessner, A. ; Huettmann, G. ; Kuehnle, W. ; [weitere]

s.l. : American Chemical Society

The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 14923-14930

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Quelle: ACS Legacy Archives

Thema: Chemie und Pharmazie , Physik

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1021/j100041a005

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5

Digitale Medien

Degradation efficiency and molecular size alteration during the aerobic microbial treatment of lignite pyrolysis deposit water (1996)

Martius, G. G. S. ; Wießner, A. ; Stottmeister, U.

Springer

Applied microbiology and biotechnology 45 (1996), S. 692-699

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ISSN: 1432-0614

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: Abstract Investigations into aerobic biological degrada-tion were carried out as part of an extensive programme designed to facilitate the cheap remediation of a pyrolysis waste-water deposit. Attention was focused on the processes of carbon conversion by different populations. The susceptibility of a body of lignite-processing deposit water to microbiological degradation was examined in batch investigations in a Sapromat system and in continuous bench-scale fermenter cultivations, with respect to nutrient supply, inoculation culture and molecular size distribution. It was found that degradation best occurs with an adapted mixed culture. The autochthonous culture removes 30% less dissolved organic carbon (DOC) and has a 40% higher specific oxygen demand. A shortage of phosphorus, investigated with a view to avoiding additional eutrophication problems in the open water in the case of in situ remediation, causes reduced DOC degrada-tion and significantly higher specific oxygen demand. The biological process is overlapped by abiotic oxidation. During aerobic treatment, a concentration of colour-giving aromatic substances of between 0.5 kDa and 5 kDa was observed. This phenomenon is caused by the oxidation of low- and high-molecular-mass compounds. The removal of DOC is limited to 65% and mainly occurs in the range below 0.5 kDa (30%) and in the 0.5–1 kDa range (12%); the removal is negligible in the ranges 1–3 kDa (0.8%) and 3–5 kDa (2%) and a little higher in the ranges 5 kDa–0.3 μm (5%) and above 0.3 μm (6%). In the investigations it was discovered that DOC removal causes in the ranges below 0.5 kDa, 0.5–1 kDa and 5 kDa–0.3 μm mainly as a result of degradation, but the range above 0.3 μm is chiefly caused by bioadsorption. Aerobic microbiological treatment is able to remove most low-molecular-mass substances. In order to remove the macromolecular and colour-giving part of the deposit water, an additional treatment stage, e.g. flocculation, is required.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s002530050750

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6

Digitale Medien

Spectro-streak picosecond studies of intramolecular charge-transfer fluorescence (1994)

Staerk, H. ; Wiessner, A. ; Kühnle, W.

Springer

Journal of fluorescence 4 (1994), S. 87-90

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ISSN: 1573-4994

Schlagwort(e): Spectro-streak photometer ; picosecond excitation ; intramolecular charge transfer

Quelle: Springer Online Journal Archives 1860-2000

Thema: Physik

Notizen: Abstract A spectro-streak photometer, an instrument for simultaneously measuring fluorescence intensity, time, and wavelength,I(t, λ), with a single picosecond excitation pulse, has been constructed. Two typical and currently highly topical examples of mesurements are discussed. (1) the temporal development of the fluorescence form the intramolecular charge-transfer (ICT) state of the rigid aromatic compound 4,5-(1′-methylindolino)3,4-naphthanthracene is studied in the protic solvent hexanol. (2) Propyl chain-linked pyrene/N,N-dimethylaniline is used as the model compound to study conformational changes associated with the transition from a contact ion pair to a sandwich exciplex.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01876662

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