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 Fe (23+) ions plan nar-channeling in the (2 2 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 2(s1/2)-3(s1/2), 2s(1/2)-3d(3/2) and 2s(1/2)-3d(5/2) transitions were observed as well as the resonance dips at transition energies corresponding to the optically allowed 2s(1/2)-3p(1/2) and 2s(1/2)-3p(3/2) transitions. (c) 2004 Elsevier B.V. All rights reserved.