Comment on “Desorption of carbon dioxide molecules from a Pt(111) surface: A stochastic classical trajectory approach”

✍ Scribed by Bret Halpern; Moris Kori

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 336 KB
• Volume: 159
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(89)87540-2

✦ Synopsis

We examine the claim of Kwong, De Leon and Hailer that energy disposal in the P&catalyzed oxidation of CO is non-statistical. We find that their main arguments do not support that claim.

As an interpretation of their trajectory study of CO2 desorption, Kwong, De Leon and Haller (KDH) propose a "non-statistical channeling of the CO + 0 reaction energy into the various internal modes of the desorbed COz" [ 11. This, they point out, contradicts our previous suggestion [ 21 that energy disposal is "to a first approximation statistical". We disagree with their interpretation, and we believe that their arguments do not support it.

Before examining their arguments, we note that KDH do not state any general criterion for distinguishing between statistical and non-statistical energy disposal. The most straightforward approach to making that distinction is to compute the statistical, "prior" energy distributions [ 3 1, which, in gas phase reactions, depend only on the number of energy states available to the reaction products. The prior distribution then serva as a reference to which an experimental or computed distribution may be compared. KDH have not computed any prior distributions.

In a surface-catalyzed reaction, the prior distributions will depend on what one designates as reaction products. In CO oxidation, one product must be the desorbed CO,. The other may be taken as the entire solid, or a smaller cluster of atoms near the surface of that solid. In the former case, the prior distributions for the desorbed molecule would be Boltz-