Experimental Collision Cross Sections
The reduced mobility K0 of an ion drifting through a buffer gas, discussed in the previous section, can be related to its collision cross section using kinetic theory.
this expression, e is the charge on the ion, N0
the buffer gas number density at P0 and T0,
μ the reduced mass of the buffer gas
and ion, T the effective temperature, and
the momentum transfer collision integral. Thus, by measuring K0
we obtain a value for ,
an experimental "cross section".
for similar shapes, differences between
and are similar and
can be corrected for empirically. Differences between
and are largest (up
to 20%) for exotic geometries with large concave surfaces like bowls.
(See e.g. Shvartsburg,
A. A.; Jarrold, M. F. Chem. Phys. Lett. 1996, 261,
86-91 and Shvartsburg,
A. A.; Schatz, G. C.; Jarrold, M. F. J. Chem. Phys. 1998,