Feshbach resonances associated with Rydberg states of the hydrogen halides

Abstract

Using an electron transmission spectrometer we locate Feshbach resonances in the hydrogen halides HF, HCl, HBr, and HI. These resonances consist of two Rydberg electrons bound to a positive ion core grandparent state. By analysis of previously published data, we determine the electron configurations of resonances observed in the isoelectronic rare gases and hence deduce the electron configurations of the resonances observed in HCl, HBr, and HI. We find that most of the observed resonances whose grandparent positive ion states have term value X ²Π are associated with Rydberg parent states of symmetry [X ²Π]nsσ, [X ²Π]npσ, and [X ²Π]ndλ. In HF, only one resonance series, associated with the [X ²Π]3sσ ^1,3Π Rydberg state is observed.