Reaction and relaxation of vibrationally excited formyl radicals

Abstract

Ground state and vibrationally excited formyl radicals were produced by excimer laser (308 nm) photolysis of formaldehyde and glyoxal at 295 K. The subsequent evolution of the (0,1,0) and (0,0,0) vibrational levels was monitored through time-resolved laser resonance absorption. Rate constants of (6.4±1.0)×10−12, (3.0±0.5)×10−12, (2.5±0.3)×10−13, (2.5±0.8)×10−13, (3.4±0.4)×10−11, and (9.4±1)×10−12 cm3 molecule−1 s−1 were determined for removal of HCO(0,1,0) by (HCO)2, H2CO, He, N2, NO, and O2, respectively. Upper limits of 8.0 ×10−12 and 4.4×10−12 cm3 molecule−1 s−1 were established for reactive removal of HCO(0,1,0) by NO and O2. The rate constant for relaxation of an unidentified higher vibrational level of HCO to (0,1,0) by (HCO)2 was measured to be (2.4±0.4)×10−11 cm3 molecule−1 s−1 and rate constants of (7±2)×10−13 and (2.6±0.6)×10−11 cm3 molecule+1 s−1, respectively, were determined for removal of DCO(0,1,0) by D2CO and NO. The relaxation and reaction rates with NO and O2 are understood in terms of the formation and decomposition of an HCONO and HCOO2 collision complex.