Experimental determination of the rate constants of the reactions of HO2 + DO2 and DO2 + DO2

0518926 - ÚFCH JH 2021 RIV US eng J - Journal Article
Assali, M. - Rakovský, Jozef - Votava, Ondřej - Fittschen, Ch.
Experimental determination of the rate constants of the reactions of HO2 + DO2 and DO2 + DO2.
International Journal of Chemical Kinetics. Roč. 52, č. 3 (2020), s. 197-206. ISSN 0538-8066. E-ISSN 1097-4601
Grant - others:PHC Barrande(FR) 38203MP
Institutional support: RVO:61388955
Keywords : DO2 radicals * HO2 radicals * kinetics
OECD category: Physical chemistry
Impact factor: 1.462, year: 2020
Method of publishing: Limited access

The rate constants of the reactions of DO2 + HO2 (R1) and DO2 + DO2 (R2) have
been determined by the simultaneous, selective, and quantitative measurement ofHO2
and DO2 by continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near
infrared, coupled to a radical generation by laser photolysis. HO2 was generated by
photolyzing Cl2 in the presence of CH3OH and O2. Low concentrations of DO2 were
generated simultaneously by adding low concentrations of D2O to the reaction mixture,
leading through isotopic exchange on tubing and reactor walls to formation of
low concentrations of CH3OD and thus formation of DO2. Excess DO2 was generated
by photolyzing Cl2 in the presence of CD3OD and O2, small concentrations of
HO2 were always generated simultaneously by isotopic exchange between CD3OD
and residual H2O. The rate constant k1 at 295 K was found to be pressure independent
in the range 25–200 Torr helium, but increased with increasing D2O concentration
k1 = (1.67 ± 0.03) × 10−12 × (1 + (8.2 ± 1.6) × 10−18 cm3 × [D2O]
cm−3) cm3 s−1. The rate constant for the DO2 self-reaction k2 has been measured
under excess DO2 concentration, and the DO2 concentration has been determined
by fitting the HO2 decays, now governed by their reaction with DO2, to
the rate constant k1. A rate constant with insignificant pressure dependence was
found: k2 = (4.1 ± 0.6) × 10−13 (1 + (2 ± 2) × 10−20 cm3 × [He] cm−3) cm3
s−1 as well as an increase of k2 with increasing D2O concentration was observed:
k2 = (4.14 ± 0.02) × 10−13 × (1 + (6.5 ± 1.3) × 10−18 cm3 × [D2O] cm−3) cm3 s−1.
The result for k2 is in excellent agreement with literature values, whereas this is the
first determination of k1.
Permanent Link: http://hdl.handle.net/11104/0303930