Effect of noncovalent interactions on conformers of the n-butylbenzene monomer studied by mass analyzed threshold ionization spectroscopy and basis-set convergent ab initio computations

Xin Tong, Jiri Cerny, Klaus Mueller-Dethlefs, Caroline EH Dessent

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Abstract

Two conformational isomers of the aromatic hydrocarbon n-butylbenzene have been studied using two-color MATI (mass analyzed threshold ionization) spectroscopy to explore the effect of conformation on ionization dynamics. Cationic states of gauche-conformer III and anti- conformers IV were selectively produced by two-color excitation via the respective S, origins. Adiabatic ionization potentials of the gauche- and anti-conformations were determined to be 70146 and 69872 +/- 5 cm(-1) respectively. Spectral features and vibrational modes are interpreted with the aid of MP2/cc-pVDZ ab initio calculations, and ionization-induced changes in the molecular conformations are discussed. Complete basis set (CBS) ab initio studies at MP2 level reveal reliable energetics for all four n-butylbenzene conformers observed in earlier two-color REMPI (resonance enhanced multiphoton ionization) spectra. For the So state, the energies of conformer III, IV and V are above conformer I by 130, 289, 73 cm(-1), respectively. Furthermore, the combination of the CBS calculations with the measured REMPI, MATI spectra allowed the determination of the energetics of all four conformers in the S-1 and D-0 states.

Original languageEnglish
Pages (from-to)5866-5871
Number of pages6
JournalJournal of Physical Chemistry A
Volume112
Issue number26
DOIs
Publication statusPublished - 3 Jul 2008

Keywords

  • DER-WAALS COMPLEXES
  • ENERGY PHOTOELECTRON-SPECTROSCOPY
  • ZEKE
  • RESOLUTION
  • CATION
  • CLUSTERS
  • SPECTRA
  • PROPYLBENZENE
  • CONFORMATION
  • ENERGETICS

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