Theory of spin polarisation phenomena in molecular photoionisation processes

The angular distribution of molecular photoelectrons with defined spin orientation ejected by polarised or unpolarised light from unoriented diatomic or linear polyatomic molecules is derived in the dipole approximation. Its general structure is the same as in atoms and is defined by five independent parameters. Expressions for these parameters in terms of dipole matrix elements and phaseshift differences are presented. The influence of the spin-orbit interaction both in bound states and in the continuous spectrum is discussed. The degree of polarisation of molecular photoelectrons is expected to be lower than atomic photoelectrons due to the greater number of allowed transitions in molecules.