Determination of the Rate Constants of the Reactions Cr + O2 + M → CrO2 + M and Cr + O2 → CrO + O

• Published in: Kinetics and catalysis Vol. 62; no. 4; pp. 472 - 478
• Main Authors: Vlasov, P. A., Ploskirev, A. E., Smirnov, V. N.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-07-2021; Springer Nature B.V
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Chromium; Electron states; Low pressure; Oxygen; Physical Chemistry; Rate constants; rate constants; recombination; RRKM model; chromium atoms; molecular oxygen; exchange reaction
• DOI: 10.1134/S002315842104011X
• EISSN: 1608-3210
• ISSN: 0023-1584

The rate constants of the interactions of chromium atoms with molecular oxygen through recombination Cr + O
2
+ M → CrO
2
+ M (I) and exchange Cr + O
2
→ CrO + O (II) were determined by a new method for treatment of experimental data. The results, together with the available literature data, led to the following equations for the rate constants of recombination in the low-pressure limit and of the exchange reaction:
cm
6
mol
–2
s
–1
,
, cm
3
mol
‒1
s
‒1
. An expression for the rate constant of the reverse reaction was obtained from
k
2
(
T
) and the equilibrium constant for reaction (II):
cm
3
mol
‒1
s
‒1
. Modeling within the framework of the RRKM theory shows that calculation of the rate constant
k
1,0
(
T
) requires inclusion of not only the ground electronic state of the CrO
2
molecule, but also the low-lying excited electronic states up to the dissociation threshold. A comparison of the experimental and calculated temperature dependences shows that the best agreement between them is achieved at an average portion of energy transferred in deactivating collisions of the excited CrO
2
molecule with diluent gas molecules of Δ
E
= 2.8 kJ/mol.