No abstract

No abstract

No abstract

Fluorescence, excitation, and pulsed fluorescence measurements have been made on a single crystal of CaWO4 over a wide temperature range. The temperature dependences of the integrated fluorescence intensities and lifetimes were obtained for different excitation wavelengths. A sharp increase in the fluorescence lifetimes is observed below about 75°K and zero-phonon lines can be observed. These results are used to formulate a model for the tungstate luminescent center based on the WO42− ion in a crystal field of S4 symmetry. Energy migration and impurity trapping effects are also discussed.

A comparison of the spectroscopic parameters of Raman-active vibronic modes in various crystalline materials with a view to the use of these crystals for stimulated Raman scattering (SRS) is presented. It includes data on the Raman frequency shift, linewidth, integral, and peak Raman scattering cross sections. For steady-state SRS the highest Raman gain coefficient has been proved to be in barium nitrate and sodium nitrate crystals; for transient SRS it is expected to be in lithium niobate and tungstate crystals. Barium tungstate and strontium tungstate are proposed as new highly efficient Raman materials for both SRS cases.

No abstract

This paper examines the recent attempts to develop geographies of science both within, and beyond, the discipline of geography. Such efforts have been most successful in work by historical geographers and historians of geography. Investigating the `geographical turn' evident across science studies more widely, this paper considers a broad range of engagements with spatiality by historians, sociologists, anthropologists and posthumanist practice theorists. In doing so, the paper thus argues that different geographies of science are emerging. Indeed, bringing together variegated conceptions of the spatiality of scientific activity will allow for wider audiences for geographies of science, inspire further investigation of the geographical sciences, and provide resources for debates regarding disciplinary histories and futures.

No abstract