The trajectories of neutral polarizable particles in an inhomogeneous electric field

Overview & Synopsis

The trajectories of neutral polarizable particles are curved by an inhomogeneous electric field. This provides a variety of methods for measuring the polarizability (α) of neutrals. Amongst these methods, field electron microscopy seems to have been impaired so far by a lack of precision, despite its broad potentialities. The three-dimensional properties of the trajectories of polarizable particles are examined in this paper in order to determine their importance and their influence on the measurement methods. It is first shown, as a general property, that by introducing a dimensionless parameter λ and by using a scaling law, nearly all experimental situations can be analysed. In the particular case of the field electron or field ion microscope a three-dimensional calculation of the trajectories is made. The results show major differences with those of the previously existing two-dimensional theories. The velocity distribution of the particles is also considered and is found to have a non negligible influence. New graphs of fairly general validity are drawn that can be used to measure α with a field electron microscope. As an example a more correct value of the polarizability of Pb is determined (α = 9.7 ± 2.9 Å3).