110411 - Photochemistry and photosynthesis (Chapter 15...

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1 CHM3400 - Lecture 36 Apr 11 Photochemistry and photosynthesis (Chapter 15 575-586) Thermal vs. photochemical reactions Quantum yield Photosynthesis Action spectrum Redox chemistry
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2 Thermal vs. photochemical reactions How many molecules are in an excited electronic state at room temperature, if ~4x10 -19 J is the energy gap? 43 23 19 0 1 10 6 298 10 38 . 1 10 4 exp exp = = = kT E N N To increase this fraction to 1%, a temperature of 6,000 o C would be required. Conversely, UV-Vis absorption directly results in an electronically excited state S 0 S 1 Relative populations in S 0 and S 1 depend on the ……………………………………. Photochemistry can drive reactions at significant rates that would thermally be very difficult to achieve.
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Quantum yield The quantum yield for a photochemical reaction is defined as: absorbed photons of no produced molecules of no _ _ _ . _ _ _ . = Φ
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110411 - Photochemistry and photosynthesis (Chapter 15...

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