monolayer formation time τ (s)
A technique frequently used to characterize the pressure state in the high
vacuum regime is the calculation of the time required to form a monomolecular
or monoatomic layer on a gas-free surface, on the assumption that
every molecule will stick to the surface. This monolayer formation time is
closely related with the so-called impingement rate zA. With a gas at rest the
impingement rate will indicate the number of molecules which collide with
the surface inside the vacuum vessel per unit of time and surface area