TIME-RESOLVED MEASUREMENT OF O2((1)SIGMA(G)+) IN SOLUTION - PHOSPHORESCENCE FROM AN UPPER EXCITED-STATE

The second excited state 1SIGMA(g)+ of O2 has been detected for the first time in time-resolved measurements at room temperature in solution. The lifetime tau(SIGMA) of O2(1SIGMA(g)+) was determined via the 1SIGMA(g)+ --> 3SIGMA(g)- phosphorescence to be 130 +/- 10 ns in CCl4. In addition rate constants of O2(1SIGMA(g)+) quenching by several solvent molecules M have been measured in diluted solution in CCl4, allowing the estimation of values of tau(SIGMA) in pure solvents of about 20 ps in methanol, 80 ps in cyclohexane, 120 ps in acetone, 130 ps in acetonitrile and in benzene, and 1.2 ns in chloroform.