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The role of symmetry and optical selection rules in revealing the molecular structure of the lowest Rydberg and ionic states of the 1,4-diazabicyclo[2.2.2]octane-Arn (n = 1,2,3) van der Waals complexes

Belcher, D.E., Watkins, M.J., Tonge, N. and Cockett, M.C.R. (2004) The role of symmetry and optical selection rules in revealing the molecular structure of the lowest Rydberg and ionic states of the 1,4-diazabicyclo[2.2.2]octane-Arn (n = 1,2,3) van der Waals complexes. Journal of Chemical Physics, 120 (17). pp. 7894-7900. ISSN 0021-9606

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Abstract

The 1,4-diazabicyclo[2.2.2]octane–Arn (n = 1,2,3) van der Waals complexes (DABCO–Arn) have been investigated using a combination of (1 + 1[prime]) resonance enhanced multiphoton ionization (REMPI) and zero electron kinetic energy (ZEKE) spectroscopy. The additivity of the spectral shifts observed in both REMPI and ZEKE spectra, taken together with analysis of vibrational structure, suggest that in both DABCO–Ar and DABCO–Ar2 the argon atoms bind in equivalent equatorial (face) locations between two adjacent (CH2)2 bridges. However, the cumulative evidence from both REMPI and ZEKE spectra, together with ab initio results, suggests that the DABCO–Ar3 complex does not revert to D3h symmetry, but rather adopts a C2v structure in which all three argon atoms bind to one side of the DABCO framework. The exceptionally low wave-number vibrational structure observed in the REMPI spectra suggest that the van der Waals interaction in the excited state is extremely weak. However, ionization necessarily increases the strength of the interaction by virtue of the introduction of charge-induced dipole forces, as revealed by a consistent increase in vibrational wave numbers of the modes observed in the resultant ZEKE spectra.

Item Type: Article
Academic Units: The University of York > Chemistry (York)
Depositing User: York RAE Import
Date Deposited: 05 May 2009 13:00
Last Modified: 05 May 2009 13:00
Published Version: http://dx.doi.org/10.1063/1.1691765
Status: Published
Publisher: American Institute of Physics
Identification Number: 10.1063/1.1691765
URI: http://eprints.whiterose.ac.uk/id/eprint/6558

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