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Title: Observation of orbiting resonances in He({sup 3}S{sub 1}) + NH{sub 3} Penning ionization

Resonances are among the clearest quantum mechanical signatures of scattering processes. Previously, shape resonances and Feshbach resonances have been observed in inelastic and reactive collisions involving atoms or diatomic molecules. Structure in the integral cross section has been observed in a handful of elastic collisions involving polyatomic molecules. The present paper presents the observation of shape resonances in the reactive scattering of a polyatomic molecule, NH{sub 3}. A merged-beam study of the gas phase He({sup 3}S{sub 1}) + NH{sub 3} Penning ionization reaction dynamics is described in the collision energy range 3.3 μeV < E{sub coll} < 10 meV. In this energy range, the reaction rate is governed by long-range attraction. Peaks in the integral cross section are observed at collision energies of 1.8 meV and 7.3 meV and are assigned to ℓ = 15,16 and ℓ = 20,21 partial wave resonances, respectively. The experimental results are well reproduced by theoretical calculations with the short-range reaction probability P{sub sr} = 0.035. No clear signature of the orbiting resonances is visible in the branching ratio between NH{sub 3}{sup +} and NH{sub 2}{sup +} formation.
Authors:
;  [1] ;  [2] ;  [3]
  1. Institute for Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne (Switzerland)
  2. Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw (Poland)
  3. Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland)
Publication Date:
OSTI Identifier:
22415709
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 16; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; AMMONIA; ATOMS; BRANCHING RATIO; HELIUM; INTEGRAL CROSS SECTIONS; IONIZATION; MOLECULAR IONS; MOLECULE COLLISIONS; MOLECULES; PROBABILITY; QUANTUM MECHANICS; REACTION KINETICS; RESONANCE; SCATTERING