Abstract
Previous theoretical treatments of polarisation spectroscopy (forward scattering) are generalised so as to include laser temporal coherence effects. It is shown that for the general case it is impossible to describe the signal obtained in terms of birefringence and dichroism. The generalisation of the concept of the polarisability tensor is given together with the approximate expression for the signal in terms of it. The simple example of the Jg=0 to Je=1 transition in the forward scattering experiment is discussed in detail. Comparison is made between the signal lineshapes obtained for the phase diffusion model and the chaotic field model. The necessity of taking into account the statistical properties of the laser light in the forward scattering (polarisation spectroscopy) experiment is pointed out.