Editing Multipole expansion (section)

====Note on conventions====
The definition of the complex molecular multipole moment given above is the [[complex conjugate]] of the definition given in [[Spherical multipole moments#General spherical multipole moments|this article]], which follows the definition of the standard textbook on [[classical electrodynamics]] by Jackson,<ref name=Jackson75/>{{rp|137}} except for the normalization. Moreover, in the classical definition of Jackson the equivalent of the ''N''-particle [[quantum mechanics|quantum mechanical]] expectation value is an [[integral]] over a one-particle charge distribution. Remember that in the case of a one-particle quantum mechanical system the expectation value is nothing but an integral over the charge distribution (modulus of wavefunction squared), so that the definition of this article is a quantum mechanical ''N''-particle generalization of Jackson's definition.

The definition in this article agrees with, among others, the one of Fano and Racah<ref>U. Fano and G. Racah, ''Irreducible Tensorial Sets'', Academic Press, New York (1959). p. 31</ref> and Brink and Satchler.<ref>D. M. Brink and G. R. Satchler, ''Angular Momentum'', 2nd edition, Clarendon Press, Oxford, UK (1968). p. 64. See also footnote on p. 90.</ref>