Solution of the Dirac Equation for Strong External Fields

The 1s bound state of superheavy atoms and molecules reaches a binding energy of $-2m{c}^2$ at $Z\approx 169$. It is shown that the $K$ shell is still localized in $\mathcal{r}$ space even beyond this critical proton number and that it has a width $\Gamma$ (several keV large) which is a positron escape width for ionized $K$ shells. The suggestion is made that this effect can be observed in the collision of very heavy ions (superheavy molecules) during the collision.