Calculation of the photoabsorption of HF in the vacuum UV

The photoabsorption cross section of the HF molecule up to 12 eV arising from the X → A transition is computer by a large one-electron basis set of atomic natural orbitals and highly correlated wavefunctions. The quality of the results is checked by the accordance of the transition probabilities evaluated both in the dipole length and velocity gauges. Cross sections within an accuracy of 7% are obtained by multireference extended CI with selected CAS-SCF reference states. Comparison with two experimental results, in large disagreement with each other, does not permit an assessment of which experiment is more reliable.