Observation of e + e − → ηψ(2S) at center-of-mass energies from 4.236 to 4.600 GeV

Using a total of 5.25 fb −1 of e + e − collision data with center-of-mass energies from 4.236 to 4.600 GeV, we report the first observation of the process e + e − → ηψ(2S) with a statistical significance of 4.9 standard deviations. The data sets were collected by the BESIII detector operating at the BEPCII storage ring. We measure the yield of events integrated over center-of-mass energies and also present the energy dependence of the measured cross section.