Branching ratios for competing channels in the reaction of HOCO radicals with NO

Citation
Rv. Olkhov et al., Branching ratios for competing channels in the reaction of HOCO radicals with NO, PHYS CHEM P, 3(20), 2001, pp. 4522-4528
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
ISSN journal
1463-9076 → ACNP
Volume
3
Issue
20
Year of publication
2001
Pages
4522 - 4528
Database
ISI
SICI code
1463-9076(2001)3:20<4522:BRFCCI>2.0.ZU;2-G
Abstract
The yields of CO2 from the reactions of HOCO radicals with O-2 and with NO have been compared using the technique of time-resolved infrared absorption . In two separate series of experiments, HOCO radicals have been generated by (i) broadband ultraviolet photolysis of acrylic acid (CH2CHCOOH) and (ii ) the reaction, Cl+HCOOH --> HCl + HOCO, following pulsed laser photolysis of Cl-2 at 351 nm. In the latter experiments, the observed CO2 yields were corrected for the loss of Cl atoms by the reactions Cl+NO+He --> ClNO+He an d Cl + ClNO --> Cl-2 + NO. Our measurements on the rate of Cl+NO+He yield a value of the third-order rate constant of (5.1 +/- 0.7) x 10(-32) cm(6) mo lecule(-2) s(-1). The results of the main experiments show that the yield o f CO2 from the reaction between NO+HOCO is appreciably less than that from O-2 + HOCO and is dependent on the total pressure in the range 10 to 100 To rr. We interpret this as showing that the reactions and HOCO + NO --> HNO CO2 and HOCO+NO(+M) --> HOC(O)NO(+M) occur at similar rates, with the latt er reaction being favoured at the higher total pressure.