## Atomic Structure of HCI

An EBIT is well suited as a source for high resolution spectroscopy of highly charged ions. The ions are at rest to a good approximation, having no centre-of-mass velocity so a Doppler correction does not need to be applied.

In the atomic structure of HCIs, the relativistic and quantum electro-dynamics (QED) contributions are very important compared with that of neutral atoms and low charged ions. For instance, the Lamb shift in hydrogenlike ions increases in proportion to Z^{4}while the elctronic binding energies increase only as Z^{2}, so that the relative contribution of the Lamb shift increases as Z. Precise measurement of the energy levels of HCIs, then, gives a test of QED theory in the strong field regime.