Abstract
The energy of the He 1s2 → 1s2p(1P) transition for helium atoms in liquid helium, solid helium and helium bubbles in metals is greater than for free helium atoms by an amount known as the energy shift. The energy shift is calculated by combining the results of ab-initio self-consistent field electronic structure calculations with corrections to account for the effects of electron correlation. The corrections consist of a short-range correlation energy which is calculated using density functional theory and a dispersion energy which is calculated using a modified form of the van der Waals interaction. The method allows significant improvements to be made on previous calculations and the predicted values or the energy shift are in good agreement with the experimental results.