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We report an analysis of the absorption edge anisotropy in CuGeO3 based on a comparison of polarized optical data with electronic structure calculations in the framework of the extended Hückel tight binding model. Taking the z axis as parallel to the CuO4 chains, we ascribe the absorption edge in the magnetic chain direction to O 2p x , 2p y → singly filled Cu 3d transitions and the edge in the transverse direction to O 2p z → singly filled Cu 3d excitations. The dual slope in the transverse direction is a direct consequence of the double maximum in the O 2p z density of states. The influence of Zn and Si doping on the electronic spectra of CuGeO3 is analyzed as well. Whereas neither impurity affects the phonon-assisted d−d band, Si doping smears the charge-transfer gap. This smearing of the gap by interchain impurity substitution is attributed to random distortions of the crystalline lattice giving rise to structurally induced changes in the electronic properties.

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In this paper, we discuss the recent ESG's development and implementation efforts concerning its authentication infrastructure. ESG's requirements are to make the user's logon-experience as easy as possible, and to facilitate the integration of the security services and the Grid components for both the developers and system administrators. To meet that goal, we leverage existing primary authentication mechanisms, deploy a "lightweight" but secure OpenID WebSSO, deploy a "lightweight" X.509-PKI, and use autoprovisioning to ease the burden of security configuration management. We're close to finalizing the associated development and deployment.