Spectroscopic characterization of Al2O3-Ni selective absorbers for solar collectors

Cataloged from PDF version of article.Optical spectroscopy of electrochemically prepared Ni-pigmented aluminum oxide selective absorbers have been determined in the 200—20000 nm range. It was found that samples anodized under the same conditions and pigmented using nickel acetate resulted in better thermal emittance values when compared with nickel sulfate although both have comparable solar absorbance values. Electron spectroscopic investigation revealed that only a small fraction of Ni is present on the surface with an oxidation state of *#2. The O/Al ratio determined by XPS is larger than 1.5. This information together with the measured Al 2p Auger parameter indicated that the surfaces contain additional OH groups which was also confirmed by the presence of a broad hyrogen-bonded band in the region 3000—3400 cm~1 observed in the reflection—absorption IR spectra of these samples. ( 1998 Elsevier Science B.V. All rights reserved

Diffraction of complex molecules by structures made of light

We demonstrate that structures made of light can be used to coherently control the motion of complex molecules. In particular, we show diffraction of the fullerenes C60 and C70 at a thin grating based on a standing light wave. We prove experimentally that the principles of this effect, well known from atom optics, can be successfully extended to massive and large molecules which are internally in a thermodynamic mixed state and which do not exhibit narrow optical resonances. Our results will be important for the observation of quantum interference with even larger and more complex objects.Comment: 4 pages, 3 figure

XPS characterization of Co and Cr pigmented copper solar collectors

Cataloged from PDF version of article.XPS is used to characterize the chemical state of Co and Cr on the surfaces of electrochemically pigmented copper plates. Using both the measured 2p binding energies and the magnitude of the 3s multiplet splitting chemical states of 2# and 3# are assigned to Co and Cr, respectively. FTIR reflectance analyses reveal that the surfaces of the pigmented samples contain hydrogen bonded OH groups. Optimum solar absorbance and thermal emittance values obtained are a"0.92 and e"0.17, a"0.96 and e"0.04 for the Co and Cr pigmented copper collectors, respectively. ( 1999 Elsevier Science B.V. All rights reserved