Nuclear-Excited Feshbach Resonances in Electron Attachment to Molecular Clusters

Abstract

Using a high resolution ( $\ensuremath{\Delta}E\ensuremath{\approx}1\mathrm{meV}$) laser photoelectron attachment method, we have studied cluster anion formation in collisions of low energy electrons (1--180 meV) with ${\mathrm{N}}_{2}\mathrm{O}$ clusters. Both $({\mathrm{N}}_{2}\mathrm{O}{)}_{q}{\mathrm{O}}^{\ensuremath{-}}$ and $({\mathrm{N}}_{2}\mathrm{O}{)}_{q}^{\ensuremath{-}}$ ions are formed through a very sharp ``zero energy resonance.'' Strikingly narrow peaks (widths 2.3--4.4 meV) are observed in the $({\mathrm{N}}_{2}\mathrm{O}{)}_{q}{\mathrm{O}}^{\ensuremath{-}}$) ( $q\ensuremath{\ge}5$) ion yield just below the onsets for vibrational excitation of the ${\mathrm{N}}_{2}\mathrm{O}$ constituents. We interpret these peaks as nuclear-excited Feshbach resonances of temporary cluster anions $({\mathrm{N}}_{2}\mathrm{O}{)}_{N}^{\ensuremath{-}}$ dissociating into $({\mathrm{N}}_{2}\mathrm{O}{)}_{q}{\mathrm{O}}^{\ensuremath{-}}$ $(q<N)$.