Impact parameter dependent resonant coherent excitation of relativistic heavy ions planar channeled in crystals

Resonant coherent excitation of a 1s electron to n = 2 states in relativist ic 390 MeV/nucleon hydrogenlike Ar17+ ions has been observed through measur ements of the surviving charge state of Ar17+ ions planar channeled in a Si crystal. We experimentally demonstrate trajectory-dependent, i.e., impact parameter dependent resonant-coherent-excitation phenomena by measuring the energy deposition in coincidence with the charge state of emerging ions. T he resonant-coherent-excitation transition energy reflects spin-orbit (I . s) interaction and Stark effect originating in the static crystal field, wh ich is in good agreement with calculations.