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Full set of Notes with Fill-Ins - San Jose State University

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Chem 155 Unit 10 Page 191 <strong>of</strong> 316UV-Vis <strong>Ins</strong>trumentation:Light Sourcesa. D 2 Lamps – 190-400nm,• excellent UV sources• Electrical Discharge in D 2 gas in a sealed, SiO 2bulb.D 2 D 2 * (dissociative molecular state)D 2 * D a + D b + hνE = KE(D a ) + KE(D b ) + hνWavelengthKinetic Energy Continuum continuumb. Tungsten(W)-Halogen – 350-2500nm ,• excellent Vis-NIR (visible-near Infrared) sources• blackbody radiators (e.g. 2500K)• halogen helps to re-deposit W onto filament andimproves lifetime for very hot filamentsc. Xe- or Hg-arc lamps – 200-1000nm,• excellent UV-Vis sources• high-atomic number noble gas in electricaldischarge – many states many wavelengthsthat coalesce into a continuum.Materials:silica = SiO 2 (190-2500nm)glass = SiO 2 + NaBO 4 , etc. (350-1500nm)sapphire = Al 2 O 3 (180-5500nm) $$Page 191 <strong>of</strong> 316

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