title: Kinetics of chemi-ionization reactions of lanthanide metals (Nd, Sm) from 150 to 450 K.
abstract: The kinetics of chemi-ionization reactions of neodymium and samarium atoms with an oxygen atom to yield a metal monoxide cation and electron were studied using a flow tube apparatus over a temperature range of 150-450 K. Nd reacts efficiently with O, near the hard-sphere collision limit at all temperatures, with a rate constant of 3 × 10(-10) cm(3) s(-1) at 300 K and a slight positive temperature dependence. No chemi-ionization of Nd with N2O was observed, despite the reaction being exothermic. Chemi-ionization of Sm with O is slow, with a rate constant at 300 K determined to be 7 × 10(-12) cm(3) s(-1), although with large uncertainty. The Sm reaction also shows a slightly positive temperature dependence, described by a small activation energy of 60 meV. Although not definitive, the data suggest that excited states of Sm react efficiently whereas ground state Sm reacts inefficiently.
authors.affiliation: Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117, USA.
authors.forename: Shaun G
authors.initials: SG
authors.lastname: Ard
authors.affiliation: Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117, USA.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Shuman
authors.affiliation: Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117, USA.
authors.forename: Oscar
authors.initials: O
authors.lastname: Martinez
authors.affiliation: Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Brumbach
authors.affiliation: Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117, USA.
authors.forename: Albert A
authors.initials: AA
authors.lastname: Viggiano