ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Of the excited 1Π1 electronic states of van der Waals complexes of Mg, Zn, and Cd atoms (M) with rare-gas (RG) atoms, only the Zn⋅Xe (1Π1) and Cd⋅Xe (1Π1) states predissociate to form the lower-lying triplet states, Zn(4s4p 3P2) and Cd(4s4p 3P2), respectively. It has been postulated that such predissociations occur by means of potential curve crossings between bound 1Π1 levels and repulsive M⋅RG (3Σ1+) states. Since the M⋅RG (1Π1) states become more bound as the RG atom becomes more polarizable, from Ne through Xe, and the M⋅RG(3∑+) states should become more repulsive as the RG atom becomes larger in the same order, the likely reason that only the Zn⋅Xe and Cd⋅Xe 1Π1 states predissociate is that they are the only states which have 1Π1/3Σ1+ curve crossings below the energies which are accessed spectroscopically. We have carried out ab initio electronic structure calculations using various basis sets, and at various levels of correlation, to examine the repulsive 3Σ1+ potential curves of Zn⋅Ar, Zn⋅Kr, Zn⋅Xe, Mg⋅Ar, and Mg⋅Xe. These calculations support the general mechanism proposed, and show that the likely reason the Mg⋅Xe(1Π1) state does not predissociate is because the 1Π1/3Σ1+ curve crossing lies slightly above the energy region probed experimentally. It was necessary to utilize very good quality basis sets and high levels of correlated calculations to obtain agreement with experimental observations. In all cases, there was a regular decrease in the repulsive character of the M⋅RG(3Σ+) states as the basis quality and level of correlation was increased.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.466128
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