THEORIES OF VIBRATIONAL ROTATIONAL, STRENGTHS

The fundamental equation for the rotational strength of a vibrational transition derived by Stephens [1] can be transformed into several alternative forms. Atomic polar and axial tensors can be related to electric and electromagnetic nuclear shielding tensors defined by Lazzeretti and Zanasi [2], permitting rotational strengths to be expressed in terms of nuclear shielding tensors. Alternative choices of gauge also provide new forms of the equation. A new gauge choice, referred to as the Distributed Origin Gauge, is introduced. In this gauge, Stephens' equation contains two terms, the P.L and the P.RxP terms. Neglecting the former term yields the P.RxP approximation, which is formally identical to the Atomic Polar Tensor Model equation of Freedman and Nafie [3]. The Fixed Partial Charge (FPC) equation of Schellman [4] and the coupled oscillator (CO) equation of Holzwarth and Chabay [5] are approximations to the P.RxP equation.