Zn(protoporphyrin) excited state quenched by O2

Zn(protoporphyrin) quenched by O₂ at conc. (2-12) x 10^–7 mol L^–1
Solvent : EtOH/H₂O (1.2/1), 0.001 mol/L Pbuf, pH 8

k_q = 8 x 10⁹(L mol^–1 s^–1)

Experimental methods: laser flash, luminescence,
Lifetime in the absence of quencher, air free = 1300 micro sec.