“Sticking probability”的意思、由来-开放百科全书

词条

Sticking probability

释义

Notes
References

The sticking probability is the probability that molecules are trapped on surfaces and adsorb chemically. From Langmuir's adsorption isotherm, molecules cannot adsorb on surfaces when the adsorption sites are already occupied by other molecules, so the sticking probability can be expressed as follows:

where is the initial sticking probability and is the surface coverage fraction ranging from 0 to 1.

Similarly, when molecules adsorb on surfaces dissociatively, the sticking probability is

The square is owing to the fact that a disassociation of 1 molecule into 2 parts requires 2 adsorption sites. These equations are simple and can be easily understood but cannot explain experimental results.

In 1958, P. Kisliuk^[1] presented an equation for the sticking probability that can explain experimental results. In his theory, molecules are trapped in precursor states of physisorption before chemisorption. Then the molecules meet adsorption sites that molecules can adsorb to chemically, so the molecules behave as follows.

If these sites are not occupied, molecules do the following (with probability in parentheses):

adsorb on the surface chemically ()
desorb from the surface ()
move to the next precursor state ()

and if these sites are occupied, they

desorb from the surface ()
move to the next precursor state ()

Note that an occupied site is defined as one where there is a chemically bonded adsorbate so by definition it would be . Then the sticking probability is, according to equation (6) of the reference^[1],

When , this equation is identical in result to Langmuir's adsorption isotherm.

Notes

1. ^¹{{cite journal|last=Kisliuk|first=Paul|title=The sticking probabilities of gases chemisorbed on the surfaces of solids|journal=Journal of Physics and Chemistry of Solids|year=1957|volume=3|issue=1–2|pages=95–101|url=http://www.sciencedirect.com/science/article/pii/0022369757900549|doi=10.1016/0022-3697(57)90054-9}}

References

The constitution and fundamental properties of solids and liquids. part i. solids. Irving Langmuir; J. Am. Chem. Soc. 38, 2221-95 1916 {{Cite journal| doi = 10.1021/ja02268a002| year = 1916| last1 = Langmuir | first1 = I.| title = The Constitution and Fundamental Properties of Solids and Liquids. Part I. Solids| journal = Journal of the American Chemical Society| volume = 38| issue = 11| pages = 2221–2295 }}

2 : Physical chemistry|Materials science

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