Helium in superstrong magnetic fields

We investigate the helium atom embedded in a superstrong magnetic field $\gamma =100\mathrm{}–10000\mathrm{a}.\mathrm{u}.$ All effects due to the finite nuclear mass for vanishing pseudomomentum are taken into account. The influence and the magnitude of the different finite mass effects are analyzed and discussed. Full configuration interaction calculations are performed for singlet and triplet states for the magnetic quantum numbers $M=0,$ $-1,$ $-2,$ $-3,$ as well as positive and negative z parities. Up to six excited states for each symmetry are studied. With increasing field strength the number of bound states decreases rapidly and we remain with a comparatively small number of bound states for $\gamma {=10\mathrm{}}^4\mathrm{a}.\mathrm{u}.\mathrm{}$ within the symmetries investigated here.