Computer modelling of thorium doping in LiCaAlF6 and LiSrAlF6: application to the development of solid state optical frequency devices
This paper describes computer modelling of thorium doping in crystalline LiCaAlF6 and LiSrAlF6. The study has been motivated by the interest in using these materials as hosts for 229Th nuclei, which are being investigated for use as frequency standards. The dopant sites and form of charge compensation are obtained; this information is essential for the further development and optimization of these devices.
Wide band gap fluoride dielectric crystals doped with trivalent rare earth ions as optical materials for 157 nm photolithography
We investigate the possibility to use a new class of wide band gap fluoride dielectric crystals as optical elements for 157 nm photolithography. The rare earth doped or non-doped crystals can be used as passive or active optical elements in the VUV. Applications are depending on the structure of the levels of the 4f^n^-^15d electronic configuration and the strength of the interconfigurational 4f^n -> 4f^n^-^15d transitions of the trivalent rare earth ions in the dielectric fluoride host. The laser induced fluorescence and the absorption spectra of the pure LiCaAlF"6 crystal and the doped with Nd^3^+ and Er^3^+ ions were studied in the VUV region of the spectrum.
Negotiating the cultural and economic outcomes of sport heritage attractions: the case of the National Baseball Hall of Fame
ABSTRACT Contemporary museums must balance their roles as commercial entities and repositories of various, and often dissonant, heritages and histories. Sports museums in particular often have clear commercial and nostalgic aims, particularly through tourist visitation, though the extent to which they represent more challenging narratives remains unclear. This paper examines how one of the most famous sports museums in the world, the National Baseball Hall of Fame (NBHF) in Cooperstown, New York, balances its dual role as tourist attraction and repository of baseball's sometimes checkered past. It was found that different sections of the museum provide greater or lesser degrees of engagement with more controversial issues, although the commercial outputs and appeal of the museum remains clear throughout. Utlimately, the NBHF demonstrates that balancing veneration and critique in collections can be commercially prosperous, and can provide a template for other sport and popular culture museums who may be wary of incorporating more challenging narratives in their exhibits. Furthermore, the symbiotic relationship between the Hall of Fame and the village of Cooperstown, particularly in creating and maintaining cultural and economic outputs, requires further exploration.