HYPERMAGNETIZABILITY ANISOTROPY (COTTON-MOUTON EFFECT) FOR H2 AND D2

Explicitly electron-correlated wave functions have been used to calculate the hypermagnetizability anisotropy (delta-eta) for H2 and D2. This property is the essential feature of the birefringence of a material in the presence of a magnetic field (the Cotton-Mouton effect). The calculations were carried out in the framework of perturbation theory and both dispersion and vibrational effects were fully taken into account. A detailed analysis of our results is made and it is concluded that electron correlation and "pure" vibrational effects are less important than vibrational averaging and dispersion. The experimental results are only in fair agreement with our theoretical ones.