I am trying to nail down the relationship between stochastic reaction parameter and the reaction rate constant. This is much less straightforward than one might think. There's one definitive reference which connects the two, which also happens to be THE paper on simulating chemical systems in the stochastic regime. The problem is that it states some relationships as givens, when I can't figure out how those are the case from my particular background. But the more basic texts don't even talk about the reaction rate constant at the level of detail that I need in order to back up those connections with solid inference. And the frustration is that while I can find many papers via google scholar which use both terms, and thus have to relate them in similar ways (so that perhaps I can see what they reference for those steps), most of those papers require you to be a member of that website, etc. Caltech has access to many of these, but I can't use that while at home, and even when at work it can be a pain in the neck to use (have to fill out a request, wait for them to fill it, etc).
Anyways...
Here's the statement I want to back up with solid intuition/argument, should anyone happen to know a good reference: The reaction rate constant is conventionally defined to be this average reaction rate per unit volume, divided by the product of the average densities of the reactants.
The units match up fairly well (average reaction rate per unit volume is molecules per second per volume, densities are molecules per volume, so that's per second per density, which can be converted to the usual per second per concentration for bimolecular reactions, which is what we're talking about), but I don't see the connection with the average densities of the reactants.
3 comments:
Duh. I finally worked out the confusion. Time to write it all up.
The solution was simple: the average reaction rate per unit volume is the quantity we usually refer to as k*[A][B], ie, the concentration change per second of a particular species. Thus to get the actual reaction rate constant k, you need to divide that quantity by the associated concentrations/densities (just a units difference). The 'average' stuff shows up all over the place, and is why we can actually do this conversion, as it's not generally true. I was getting stuck on the reaction rate terminology, not quite connecting that with the constant part.
In terms of getting journal access from home, you actually can do that. Go to library.caltech.edu and get to the journal site by following the links at that page. (It requires many extra clicks than going directly to the journal page or from google scholar, so it is annoying, but it works.) You'll be asked for your its account and password at some point, but anything for which Caltech has online access is fair game. As far as I know, you need to do it through this page if you're doing this from your home computer (modulo VNC and whatnot to pretend you're not at home).
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