Photochemical Kinetics

Question 1

Beer-Lamber law

Answer 1

Log10(I0/I) = εcl

Question 2

Beer lambert limiting cases

Answer 2

Optically thick: εcl = large, all incident light absorbed so I roughly = 0 so amount of light absorbed only depends on I0, rate varies across sample length as there’s no single well-defined conc
Optically thin: εcl = small, little light absorbed so rate roughly constant across length

Question 3

J

Answer 3

Effective first order rate constant for absorption of photons under fixed I

Question 4

Quantum yield

Answer 4

Shows efficiency of photochemical processes

Question 5

Low quantum yield

Answer 5

Intermolecular processes = reaction, internal conversion (spin conserved), inter spin crossing (spin change), radiative loss (fluorescence)
Intramolecular processes = quenching

Question 6

Photostationary states

Answer 6

States maintained by flux of light, species concis are truly constant so contrasts SSA, doesn’t rely on low concentrations of intermediates, analysed by recognising no conc are changing so rates of all component reactions are equal