DISSOCIATIVE ELECTRON-ATTACHMENT TO NO MOLECULES AND NO CLUSTERS

Dissociative electron attachment (DA) to single NO molecules and NO cl usters is studied in two independent crossed electron-molecular-beam e xperiments with high-energy resolution including a kinetic-energy anal ysis of the O- fragment ions. It is shown that the DA cross section ex hibits a vertical onset near 7.45 eV that corresponds to the energetic threshold of the DA channel O- (P-2) + N(D-2). No indication of the ground-state channel O-(P-2) + N(S-4) [O. J. Orient and A. Chutjian, P hys. Rev. Lett. 74, 501 (1995)] and no indication of long-lived N- [H. Hiraoka, R. K. Nesbet, and L. W. Welsh, Jr., Phys. Rev. Lett. 29, 130 (1977)], as recently proposed, could be found. O- formation from NO c lusters shows the same features as from single NO molecules, indicatin g the same reaction mechanism, thus also excluding coupling to the gro und-state DA channel clusters.