The hypermagnetizability of molecular oxygen

The hypermagnetizability and the hypermagnetizability anisotropy of the oxygen molecule are computed using cubic response theory applied to multi-configurational self-consistent field wave functions. The effects of basis set, electron correlation, frequency dispersion, zero point vibrational averaging and pure vibrational contributions are discussed. The result for the anisotropy (Delta(eta)=+2.65 a.u. at lambda=632.8 nM), even taking into account possible limitations in the treatment of electron correlation and in the incompleteness of the basis set, maintains a different sign and is more than two orders of magnitude smaller than the experimental values published in the literature. Possible reasons for this large discrepancy are discussed. (C) 1997 American Institute of Physics.