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Keld L. Bak

Ab initio studies of ground and excited electronic states of MgAr, CdAr, and BeAr

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  • Jerry A. Boatz, University of Utah
  • ,
  • Keld Lars Bak
  • Jack Simons, University of Utah

The ground state (X1Σ+) and several excited state (A3Π, c3Σ+, C1Π, D1Σ+, and E3Σ+) potential energy surfaces for the diatomic molecules MgAr, CdAr, and BeAr have been computed using complete active space self-consistent field (CASSCF) wavefunctions and valence double- and triplezeta quality basis sets augmented with polarization and diffuse functions. Pump-and-probe laser experiments have examined the quenching, of excited singlet states of metal-rare gas complexes such as CdXe to produce triplets that dissociate to3PJmetal atoms. This quenching, which is detected for CdXe but not for CdAr or MgAr, is thought to occur via a crossing or strong coupling of a repulsive triplet curve correlating to the underlying3P state of the metal, with an attractive singlet curve that correlates to the higher1P state of the metal. The present work indicates that the attractive C1Π and repulsive c3Σ+ curves of MgAr and CdAr do not intersect in the energetically accessible region of the C1Π surface, unlike the corresponding curves for the CdXe diatom. These data are consistent with the absence of3PJ Cd atoms in the MgAr and CdAr experiments, respectively. However, an alternative quenching mechanism involving "vibronic" coupling between the C1Π vibrational eigenstates and the continuum eigenstates of the underlying repulsive3Σ+ surface may be operative; this possibility is examined qualitatively and predicted to be unlikely for MgAr (due to small spin-orbit coupling) and CdAr (due to unfavorable vibronic factors). BeAr, which has yet to be probed experimentally, is predicted to be bound by 770 and 900 cm-1 in the D1Σ+ state (which has metal 2 s2 p character) and the E3Σ+ state (which has Rydberg metal 2 s3 s character), respectively, and to display interesting potential curve intersections.

Original languageEnglish
JournalTheoretica chimica acta
Pages (from-to)209-225
Number of pages17
Publication statusPublished - May 1992

    Research areas

  • BeAr, CASSCF, CdAr, Excited states, Ground states, MgAr

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