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Title: Discharge source coupled to a deceleration unit for anion beam generation: Application to H{sub 2}{sup −} photodetachment

A cathode discharge source coupled to a deceleration unit for anion beam generation is described. The discharge source, made of stainless steel or duralumin electrodes and Macor insulators, is attached to the exit nozzle valve plate at one end, and to an Einzel lens to the other end. Subsequently, a cylindrical retardation unit is attached to the Einzel lens to decelerate the ions in order to optimize the laser beam interaction time required for spectroscopic investigations. The compact device is able to produce beam intensities of the order of 2 × 10{sup 12} anions/cm{sup 2} s and 20 μrad of angular divergence with kinetic energies ranging from 30 to 120 eV. Using distinct gas mixtures for the supersonic expansion together with a linear time-of-flight spectrometer, anions of great relevance in molecular astrophysics like, for example, H{sub 2}{sup −}, C{sub 3}H{sup −}, C{sub 2}{sup −}, C{sub 2}H{sup −}, HCN{sub 2}{sup −}, CO{sub 2}{sup −}, CO{sub 2}H{sup −}, C{sub 4}{sup −}, C{sub 4}H{sup −}, C{sub 5}H{sub 4}{sup −}, C{sub 5}H{sub 6}{sup −}, C{sub 7}N{sup −}, and C{sub 10}N{sup −} were produced. Finally, in order to demonstrate the capability of the experimental technique the photodetachment cross-section of the metastable H{sub 2}{sup −}, predominantlymore » in the (v = 0, J = 26) state, was measured following laser excitation at λ{sub exc}= 565 nm obtaining a value of σ{sub ph}= 0.04 Å. To the best of our knowledge, it is the first time that this anion cross-section has been measured.« less
Authors:
;  [1]
  1. Unidad de Láseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense, Juan XXIII-1, Madrid 28040 (Spain)
Publication Date:
OSTI Identifier:
22220225
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 84; Journal Issue: 12; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ANIONS; ASTROPHYSICS; BEAMS; CARBON DIOXIDE; CATHODES; CROSS SECTIONS; DURALUMIN; HYDROCYANIC ACID; HYDROGEN; HYDROGEN 5; HYDROGEN IONS; PHOTON-MOLECULE COLLISIONS; STAINLESS STEELS; VALVES