I must vaporize a molecule with a normal boiling point of 320°C. Now I work with ultra-high vacuum and I need to bring my molecule to the gas phase. Has anyone a rough idea how high the temperature has to be, to bring my molecule to the gas phase with a pressure of $\pu{5E-8 mbar}$.

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    $\begingroup$ The vapor pressure increases with temperature as described by the Clausius–Clapeyron Equation. One parameter you need to know is the heat of vaporization, which correlates with the strength of intermolecular interactions. Without knowing the type or size of the molecule, there is no way to make the estimate. $\endgroup$ – Karsten Theis Jun 9 at 14:15
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    $\begingroup$ I am afraid there are no precise answer to this question. It only depends on the nature of the interaction between your molecule and the walls. $\endgroup$ – Maurice Jun 9 at 14:15
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    $\begingroup$ Have a look for the method called MALDI used in mass spectrometry to do what you want. $\endgroup$ – porphyrin Jun 9 at 15:56
  • $\begingroup$ Molecules don't have boiling points, substances do. BTW melting point is more important - it's not like you need you boil something to vaporise. $\endgroup$ – Mithoron Jun 9 at 20:28
  • $\begingroup$ Like @porphyrin said, please look at MALDI! The wikipedia article is here. Heating is only one way to get big molecules up and going! $\endgroup$ – Ed V Jun 9 at 21:51