Nonequilibrium excitation of C2 radicals during the thermal decomposition of C3O2 behind shock waves

C-2 concentrations and populations of the ground and the first excited vibrational levels of electronically excited C-2(d(3)Pi) radicals during the thermal decomposition of C3O2 behind shock waves were monitored by emission and absorption measurements in the (0-0) and the (1-0) Swan-bands. Experiments were carried out in mixtures of 1% C3O2 + Ar and 1% C3O2 + He at T = 2100-3200 K and p =1.5-7.5 bar. In the whole range of conditions studied an essential nonequilibrium of electronic and vibrational states of nascent C-2 radicals was observed. For analyzing possible formation and consumption reactions of the excited C-2 radicals, a convenient kinetic scheme of the C3O2 decomposition was developed, which considers both the recombinative pumping process and exchange and quenching reactions of the C-2(d(3)Pi, v = 0, 1) states.