Wave Function for the Interstitial Hydrogen Atom in SrF 2

To interpret the EPR and ENDOR results for the H   i 0center in SrF 2 two different models are used to describe the wave function of the unpaired electron. Using the Heitler‐London and the molecular orbital models the importance of the Pauli repulsion and covalence to the evaluation of the magnetic hyperfine constants is discussed. Introducing covalence in a phenomenological manner the measured data are reproduced fairly accurately. Also the inconvenience of introducing covalence using the Heitler‐London scheme together with the Löwdin transformation is discussed.