Photoionisation of helium above the N=2 threshold

The relative distribution of the ions between the 2s and 2p states in the photoionisation of helium near the n=2 threshold is examined. The influence of short-range correlations and the long-range Coulomb potential and the dipole coupling between the 2s and 2p states is separated by applying multichannel quantum defect theory. It is argued that a measured value of Gamma =1.48*10 -4 eV and q=3.55 for the 3- resonance would be consistent with sigma (2p)/ sigma (2s) approximately 3.5 at the threshold.