Dissociative electron attachment to NO molecules and NO clusters

Abstract

Dissociative electron attachment (DA) to single NO molecules and NO clusters is studied in two independent crossed electron--molecular-beam experiments with high-energy resolution including a kinetic-energy analysis of the ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ fragment ions. It is shown that the DA cross section exhibits a vertical onset near 7.45 eV that corresponds to the energetic threshold of the DA channel ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}{(}^{2}P)+{\mathrm{N}}^{*}{(}^{2}D).$ No indication of the ground-state channel ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}{(}^{2}P)+\mathrm{N}{(}^{4}S)$ [O. J. Orient and A. Chutjian, Phys. Rev. Lett. 74, 501 (1995)] and no indication of long-lived ${\mathrm{N}}^{\mathrm{\ensuremath{-}}}$ [H. Hiraoka, R. K. Nesbet, and L. W. Welsh, Jr., Phys. Rev. Lett. 29, 130 (1977)], as recently proposed, could be found. ${\mathrm{O}}^{\mathrm{\ensuremath{-}}}$ formation from NO clusters shows the same features as from single NO molecules, indicating the same reaction mechanism, thus also excluding coupling to the ground-state DA channel clusters.