149 



Daniel Rubinstein 

 It follows that 



1, r A 1, 



[A] + [A^] = [A^]^^ =[AJ (6) 



By combining equations (5) and (6): 



^' ki+k2([A^];;;,-[A^]) 



(7) 



The q\iantuin reqmrement is the number of quanta needed for the ^ 

 appearance of an absorption band corresponding to a jingle molecule A . 

 Eq. (7) predicts that the initial rate of formation of A ^^^ll be propor- 

 tional to the absorbed light intensity. The ratio d [A ] / KI^ when 



[A"*"] > has been defined as the quantimi yield y by Olson and 



Chance (4) and others (3) (11). In the above equation 



AJAi \^l^\^, (8) 



7 = 



dt = 



KI^ k-Tk^fAl] 



max 



A^ > 



The steady state expression following from (7) is 



I k k k (9) 



0=13 + o 



Only absorption changes, not concentration changes are actually 

 observed; concentrations can be converted to absorbances (optical 

 densities by dividing them by e (since OD = e [A1] ). Rearranging the 

 terms, we obtain: 



I k_ k^ k„ (10) 



o 3 13 



OD - .K k2K(OD^^^-OD) 



