KINETICS OF C2O RADICALS FORMED IN THE PHOTOLYSIS OF CARBON SUBOXIDE AT 308 AND 248 NM

The photolysis of carbon suboxide (C3O2) at 248 and 308 nm was investigated by monitoring laser-induced fluorescence (LIF) of the product C2O(X3-SIGMA-). At 308 nm the C2O(X3-SIGMA-) appears immediately after the photolysis flash followed by a slow decay. This clean source of C2O(X3-SIGMA-) was used to measure rate constants for reactions with O2 and CO and to set an upper limit on its reactivity with CO2. Measurements were also made of rate constants for the quenching of C2O(A3-PI(i)) by N2, SF6, CO and CO2. At 248 nm the LIF signal starts at a small value and increases for several hundred microseconds before decaying. Both the maximum intensity of the LIF signal and its rate of rise can be increased by adding CO. It is concluded that photolysis at 248 nm initially forms one of the low-lying singlet states Of C2O, probably a1-DELTA, and that most of this singlet state is lost by reaction with C3O2. CO has the unique ability to convert the singlet state of C2O to the X3-SIGMA- state by intersystem crossing on the attractive C3O2 surface. A semiquantitative model for this system has been proposed and its agreement with the experimental results is discussed.