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Title: Rovibronic structure in slow photoelectron velocity-map imaging spectroscopy of CH{sub 2}CN{sup −} and CD{sub 2}CN{sup −}

We report high-resolution anion photoelectron spectra of the cryogenically cooled cyanomethide anion, CH{sub 2}CN{sup −}, and its isotopologue, CD{sub 2}CN{sup −}, using slow photoelectron velocity-map imaging (SEVI) spectroscopy. Electron affinities of 12 468(2) cm{sup −1} for CH{sub 2}CN and 12 402(2) cm{sup −1} for CD{sub 2}CN are obtained, demonstrating greater precision than previous experiments. New vibrational structure is resolved for both neutral species, especially activity of the ν{sub 5} hydrogen umbrella modes. The ν{sub 6} out-of-plane bending mode fundamental frequency is measured for the first time in both systems and found to be 420(10) cm{sup −1} for CH{sub 2}CN and 389(8) cm{sup −1} for CD{sub 2}CN. Some rotational structure is resolved, allowing for accurate extraction of vibrational frequencies. Temperature-dependent SEVI spectra show marked effects ascribed to controlled population of low-lying anion vibrational levels. We directly measure the inversion splitting between the first two vibrational levels of the anion ν{sub 5} umbrella mode in both species, finding a splitting of 130(20) cm{sup −1} for CH{sub 2}CN{sup −} and 81(20) cm{sup −1} for CD{sub 2}CN{sup −}. Franck-Condon forbidden activity is observed and attributed to mode-specific vibrational autodetachment from the CH{sub 2}CN{sup −} and CD{sub 2}CN{sup −} dipole bound excited states. We also refine themore » binding energy of the anion dipole bound states to 39 and 42 cm{sup −1}, respectively, for CH{sub 2}CN{sup −} and CD{sub 2}CN{sup −}.« less
Authors:
;  [1] ;  [1] ;  [2]
  1. Department of Chemistry, University of California, Berkeley, California 94720 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22253459
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 10; 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; ACCURACY; ANIONS; BINDING ENERGY; BOUND STATE; DIPOLES; EXCITED STATES; PHOTOELECTRON SPECTROSCOPY; SPECTRA; TEMPERATURE DEPENDENCE