First observation of a proton intruder band below the Z = 50 major shell gap. Spectroscopy of 111In

An intruder band based on an h112 proton has been observed in 111In. This is the first case to be identified below the Z = 50 major shell gap. As such, it sheds light on the relative importance of the deformed 2p-2h Sn-core state and the πh112 intruder orbital to the onset of deformation near the Z = 50 “magic” proton number.