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Photochemical kinetics
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Intensity
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Transmittance Absorbance
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Transmittance Absorbance Beer’s Law
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dP(x)/dx = -κ P(x) P(x) = exp(-κ x)
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Beer’s law
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Molar extinction Coefficient ~250 L.mol -1 cm -1 Cross section ~10 -18 cm 2
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ε = 313 M -1 cm -1 b = 2 cm T = 3.16% = 0.0316 A = -logT = 1.50 c = 1.5/(313 M -1 ) (2 cm -1 ) = 0.0024 M
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NB 1: Beer fails when photochemistry happens NB 2: The photophysics Is hidden in σ (So we haven’t done much yet)
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Absorption of a mixture
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Isosbestic point
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Photochemical kinetics STEADY STATE HYPOTESIS
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Ozone production Photochemical kinetics λ ≤ 240 nm λ ≤ 280 nm
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λ ≥ 280 nm
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1.Steady state hypothesis: d[O]/dt = 0 2.Solve for [O] 3.Plug into disappearance rate of [O 3 ]
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