Origin invariance of the fully retarded rotational strength

Abstract

The gauge invariance of the rotational strength is examined. It is shown that the invariance of the rotational strength derived in the quantized field formalism follows only when all terms (to order e²) are retained in the T-matrix from which the rotational strength is derived. The gauge invariance of the semiclassical theory of natural circular dichroism is discussed. The origin invariance of the Schrödinger equation is considered and the difficulties associated with making truncated expansions of the retardation factors for the rotational strength are outlined.