Spectroscopy and quantum dynamics of the 1,2-dimethylnaphthalene·Ar van der Waals complex

Thierry Droz, Samuel Leutwyler, Margaret Mandziuk, Zlatko Bačić

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We report a detailed experimental and theoretical study of the intermolecular vibrational levels of the 1,2-dimethylnaphthalene·Ar van der Waals complex in the S1 electronic state. Due to the low symmetry of the aromatic molecular substrate, excitations in all three van der Waals modes (two in-plane, one out-of-plane) are allowed in the electronic spectrum, leading to the most complete data set of intermolecular vibrational transitions measured so far for an atom-large molecule complex. Two-color resonant two-photon ionization spectra reveal twelve bands within ≈95 cm-1 of the electronic origin. Accurate quantum three-dimensional calculations of the van der Waals vibrational levels were performed, using a method based on the 3D discrete variable representation. Combination of theory and experiment allowed a complete and quantitative interpretation of the level structure, as well as an accurate parametrization of the intermolecular potential energy surface (PES), modeled as sum of atom-atom Lennard-Jones pair potentials. The parametrization was partly transferable from other aromatic molecules, but methyl group parameters had to be adapted. Quantum number assignments of the vibrational states were possible for the low-lying levels, but difficult or impossible for states at higher energies, due to strong mode coupling, mainly between the two in-plane modes.

Original languageEnglish (US)
Pages (from-to)4715-4725
Number of pages11
JournalThe Journal of Chemical Physics
Issue number12
StatePublished - 1995

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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