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 investi gated by monitoring laser-induced fluorescence (LIF) of the product C2 O(X3-SIGMA-). At 308 nm the C2O(X3-SIGMA-) appears immediately after t he photolysis flash followed by a slow decay. This clean source of C2O (X3-SIGMA-) was used to measure rate constants for reactions with O2 a nd CO and to set an upper limit on its reactivity with CO2. Measuremen ts 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 va lue and increases for several hundred microseconds before decaying. Bo th 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 ini tially forms one of the low-lying singlet states Of C2O, probably a1-D ELTA, and that most of this singlet state is lost by reaction with C3O 2. CO has the unique ability to convert the singlet state of C2O to th e X3-SIGMA- state by intersystem crossing on the attractive C3O2 surfa ce. A semiquantitative model for this system has been proposed and its agreement with the experimental results is discussed.