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Outgassing, vacuum question

  1. Oct 2, 2006 #1
    I'm trying to calculate the outgassing rate for the following problem, but I seem to be missing something (maybe the like the pumping speed or time).

    The base pressure of a particular vacuum system is 10^-9 torr. A sample with a fingerprint of area ~1 cm^2 is introduced into the system, resulting in an increased pressure of 2 x 10^-9 torr. Assume that the chamber of 2000 cm^2 is at 300 K, and that the molecules that outgas are not re-adsorbed on the chamber walls.

    a) What is the outgassing rate (per unit area) of the fingerprint?
    b) What is the effective vapor pressure of the fingerprint material?
    c) Making reasonable assumptions about the thickness of a fingerprint, estimate how long it will last.

    I know that the outgassing rate, in units of liter-torr/s, can be related to the pressure and the number of molecules in the system. But I'm not sure how to relate them. And I'm not sure how to find vapor pressure.

    Thanks in advance.
  2. jcsd
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