Excitation cross sections of $\mathrm{YII}$ singlet levels during $e$–$\mathrm{Y}$ collisions

The excitation of singlet levels of a singly charged yttrium ion during collisions of slow electrons against yttrium atoms is investigated experimentally. At the electron energy of $50$ eV, the excitation cross sections of $\mathrm{YII}$ $32$ spectral lines of $\mathrm{YII}$ are measured; the electron energy dependence of the cross sections is registered in the energy range of $0$–$200$ eV for $30$ of them. Based on the obtained data, the total excitation cross sections of $11$ energy levels are calculated, as well as the contribution by cascade excitation for seven levels. Absolute values of the excitation cross sections of even and odd levels differ by less than one order of magnitude.