Why is Area under Desorption Curve (TPD) the total particles desorbed?

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nyxynyx
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I'm currently reading about Temperature Programmed Desorption (TPD) and is wondering why in the graph of desorption rate (molecules/cm2/sec) against temperature (deg C), the area under the curve is the total number of particles desorbed? Isnt the units (molecules/cm/sec/degC) if u integrate the curve?
 
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I think you’ll find it’s because although it is plotted against temperature, the temperature is really a factor of time. The desorption rate isn’t constant at each temperature, and the curve is dependent on the time spent at each previous temperature step.

So if you think of the graph as desorption rate against time (s) instead, then it become clear why the integration result isn’t what you expect.

I hope that helps. Also, here is an article on choice of adsorptive which you may find interesting:
http://www.quantachrome.co.uk/en/Adsorptives_for_Physisorption_Experiments.asp