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Title: Production of cold beams of ND{sub 3} with variable rotational state distributions by electrostatic extraction of He and Ne buffer-gas-cooled beams

The measurement of the rotational state distribution of a velocity-selected, buffer-gas-cooled beam of ND{sub 3} is described. In an apparatus recently constructed to study cold ion-molecule collisions, the ND{sub 3} beam is extracted from a cryogenically cooled buffer-gas cell using a 2.15 m long electrostatic quadrupole guide with three 90° bends. (2+1) resonance enhanced multiphoton ionization spectra of molecules exiting the guide show that beams of ND{sub 3} can be produced with rotational state populations corresponding to approximately T{sub rot} = 9–18 K, achieved through manipulation of the temperature of the buffer-gas cell (operated at 6 K or 17 K), the identity of the buffer gas (He or Ne), or the relative densities of the buffer gas and ND{sub 3}. The translational temperature of the guided ND{sub 3} is found to be similar in a 6 K helium and 17 K neon buffer-gas cell (peak kinetic energies of 6.92(0.13) K and 5.90(0.01) K, respectively). The characterization of this cold-molecule source provides an opportunity for the first experimental investigations into the rotational dependence of reaction cross sections in low temperature collisions.
Authors:
; ; ;  [1]
  1. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA (United Kingdom)
Publication Date:
OSTI Identifier:
22308579
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; APPROXIMATIONS; BEAMS; BUFFERS; CROSS SECTIONS; DENSITY; DEUTERIDES; DISTRIBUTION; EXTRACTION; HELIUM; ION-MOLECULE COLLISIONS; KINETIC ENERGY; MOLECULES; NEON; PEAKS; PHOTOIONIZATION; RESONANCE; ROTATIONAL STATES; SPECTRA