Resonant coherent excitation of 2s electron of Li-like Fe ions to the n = 3 states

We observed resonant coherent excitation of the 2s electron to the n = 3 states of 83.5 MeV/u Li-like Fe23+ ions planar-channeling in the (22¯0) plane of a Si crystal. A survival fraction of the Li-like ions was measured as a function of the angle between the incident beam and the [0 0 1] axis. Clear resonance dips corresponding to the transitions of a 2s electron to all the n = 3 states were observed. The transition of each resonance dip was identified by comparing with spectroscopic data. The resonance dips at the transition energies corresponding to the optically forbidden 2s1/2-3s1/2, 2s1/2-3d3/2 and 2s1/2-3d5/2 transitions were observed as well as the resonance dips at transition energies corresponding to the optically allowed 2s1/2-3p1/2 and 2s1/2-3p3/2 transitions.