Its melting (777 ☌) and boiling (1377 ☌) points are lower than those of calcium (842 ☌ and 1484 ☌ respectively) barium continues this downward trend in the melting point (727 ☌), but not in the boiling point (1900 ☌). It is softer than calcium and harder than barium. Strontium is a divalent silvery metal with a pale yellow tint whose properties are mostly intermediate between and similar to those of its group neighbors calcium and barium. Natural stable strontium, on the other hand, is not hazardous to health.Ĭharacteristics Oxidized dendritic strontium While natural strontium (which is mostly the isotope strontium-88) is stable, the synthetic strontium-90 is radioactive and is one of the most dangerous components of nuclear fallout, as strontium is absorbed by the body in a similar manner to calcium. With the replacement of cathode-ray tubes with other display methods, consumption of strontium has dramatically declined. At the peak of production of television cathode-ray tubes, as much as 75% of strontium consumption in the United States was used for the faceplate glass. During the 19th century, strontium was mostly used in the production of sugar from sugar beets (see strontian process). Strontium was first isolated as a metal in 1808 by Humphry Davy using the then newly discovered process of electrolysis. It occurs naturally mainly in the minerals celestine and strontianite, and is mostly mined from these.īoth strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was discovered in 1790 by Adair Crawford and William Cruickshank it was identified as a new element the next year from its crimson-red flame test color. Strontium has physical and chemical properties similar to those of its two vertical neighbors in the periodic table, calcium and barium. The metal forms a dark oxide layer when it is exposed to air. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. High abundances of HCN and C2H2 are caused in the model by stellar X-ray irradiation of the gas around the inner rim.Strontium is a chemical element it has symbol Sr and atomic number 38. The spatial structure of the line emitting regions of the different molecules is discussed. We develop a disc model with a slowly increasing surface density structure around the inner rim that can simultaneously fit the spectral energy distribution, the overall shape of the JWST spectrum of EX Lupi, and the main observed molecular characteristics in terms of column densities, emitting areas and molecular emission temperatures, which all result from one consistent disc model. We calculate infrared line emission spectra between 5 and 20 mic by CO, H2O, OH, CO2, HCN, C2H2 and H2, including lines of atoms and ions, using our full 2D predictions of molecular abundances, dust opacities, gas and dust temperatures. We apply our revised 2D models to the protoplanetary disc around the T Tauri star EX Lupi in quiescent state. We show that these assumptions are crucial for the determination of the gas heating/cooling rates and discuss how they affect the predicted molecular concentrations and line emissions. We develop a new line escape probability method for disc geometries, a new scheme for dust settling, and discuss how to apply UV molecular shielding factors to photorates in 2D disc geometry. Woitke and 5 other authors Download PDF Abstract:We introduce a number of new theoretical approaches and improvements to the thermo-chemical disc modelling code ProDiMo to better predict and analyse the JWST line spectra of protoplanetary discs. Download a PDF of the paper titled 2D disc modelling of the JWST line spectrum of EX Lupi, by P.
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