Impact Parameter Dependent Resonant Coherent Excitation of Relativistic Heavy Ions Planar Channeled in Crystals

Abstract

Resonant coherent excitation of a $1s$ electron to $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ states in relativistic 390 MeV/nucleon hydrogenlike ${\mathrm{Ar}}^{17+}$ ions has been observed through measurements of the surviving charge state of ${\mathrm{Ar}}^{17+}$ 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. The resonant-coherent-excitation transition energy reflects spin-orbit $(\mathbf{l}\ifmmode \dot{}\else \.{}\fi{}\mathbf{s})$ interaction and Stark effect originating in the static crystal field, which is in good agreement with calculations.