TY  - JOUR
A1  - Ziemann, Martin Andreas
A1  - Förster, Hans-Jürgen
A1  - Harlov, Daniel E.
A1  - Frei, Dirk
T1  - Origin of fluorapatite-monazite assemblages in a metamorphosed, sillimanite-bearing pegmatoid, Reinbolt Hills, East Antarctica
N2  - Thermobarometrical and mineral-chemical investigations by electron microprobe and LA-ICP-MS on a sillimanite- bearing pegmatoid from the Reinbolt Hills provide important constraints on the P-T-X-age relations of part of East Antarctica during Pan-African tectonism. U-Th-total Pb ages of monazite imply that the pegmatoid of originally Grenvillan age (zircon U-Pb age of ca. 900 Ma) underwent a major, late Pan-African (Cambrian) regional, granulite-facies metamorphism between 500 and 550 Ma. Most of the monazite formed during this event, as result of apatite metasomatism owing to infiltration of high-grade metamorphic fluids. Apatite-biotite and other mineral thermobarometers define the peak metamorphic temperatures and pressures with 850-950 degrees C and 0.8-1.0 GPa. The F-Cl-OH relations in apatite, and biotite, the chemistry of fluid inclusions and the presence of K-feldspar microveins suggest that the metasomatising fluid was a CO2-bearing, diluted KCl brine. The pegmatoid is the first record of monazite-(Ce) formed from fluorapatite that is rich in U (up to 2.6 Wt% UO2) and possesses Th/U ratios <1 (0.09 on average). These chemical signatures are direct reflection of the U and Th concentration patterns in the parental fluorapatite
Y1  - 2005
SN  - 0935-1221
ER  - 
TY  - JOUR
A1  - Plehn, Thomas
A1  - Ziemann, Dirk
A1  - Megow, Jörg
A1  - May, Volkhard
T1  - Frenkel to Wannier-Mott Exciton Transition: Calculation of FRET Rates for a Tubular Dye Aggregate Coupled to a CdSe Nanocrystal
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - The coupling is investigated of Frenkel-like exciton states formed in a tubular dye aggregate (TDA) to Wannier-Mott-like excitations of a semiconductor nanocrystal (NC). A double well TDA of the cyanine dye C8S3 with a length of 63.4 nm and a diameter of 14.7 nm is considered. The TDA interacts with a spherical Cd819Te630 NC of 4.5 nm diameter. Electronic excitations of the latter are described in a tight-binding model of the electrons and holes combined with a configuration interaction scheme to consider their mutual Coulomb coupling. To achieve a proper description of TDA excitons, a recently determined structure has been used, the energy transfer coupling has been defined as a screened interaction of atomic centered transition charges, and the site energies of the dye molecules have been the subject of a polarization correction. Even if both nanoparticles are in direct contact, the energy transfer coupling between the exciton levels of the TDA and of the NC stays below 1 meV. It results in FRET-type energy transfer with rates somewhat larger than 10(9)/s. They coincide rather well with recent preliminary experiments.
Y1  - 2015
U6  - https://doi.org/10.1021/jp5111696
SN  - 1520-6106
VL  - 119
IS  - 24
SP  - 7467
EP  - 7472
PB  - American Chemical Society
CY  - Washington
ER  -