The Mechanism of Chromatographic Retention - Chromatographic Interactions > Dispersive Interactions > Page 4
The theory behind dispersive interactions is complex but it can be stated that the interaction energy, (U_{D}), involved with such forces can be expressed as
where (a_{p}) | is the polarizability of the molecule, |
(v_{o}) | is the characteristic frequency of the molecule, |
(h_{p}) | is Planck's constant, |
and (l) | is the distance between the molecules. |
The polarizability (a) is the crucial factor that controls the dispersive force acting on the molecule, which, for substances that have no dipoles, is given by
where (D) | is the dielectric constant of the material |
and (n_{v}) | is the number of molecules per unit volume. |