Molecular Vertical Excitation Energies Studied with First-Order RASSCF (RAS[1,1]): Balancing Covalent and Ionic Excited States

Ab initio CI studies have been performed to determine the geometry of the ground and first electronically excited states of the chlorothioformyl radical, ClCS, and the vertical excitation energies of its ten lowest doublet states and two lowest quartet states. The results are used to construct a more complete energy level correlation diagram for the photofragmentation of Cl2CS. The lowest excited electronic state of ClCS lies only 0.79 eV (adiabatic) above the ground state. Its discovery indicates that the results of previous photofragmentation experiments may need to be reinterpreted.

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Excited states of acrolein: abinitio model studies on α,β-unsaturated carbonyl compounds

Canadian Journal of Chemistry ◽

10.1139/v82-089 ◽

1982 ◽

Vol 60 (5) ◽

pp. 601-606 ◽

Cited By ~ 11

Author(s):

Katherine Valenta ◽

Friedrich Grein

Keyword(s):

Excited State ◽

Excited States ◽

Carbonyl Compound ◽

Carbonyl Compounds ◽

Excitation Energies ◽

Vertical Excitation ◽

Model Studies ◽

Unsaturated Carbonyl Compound ◽

Vertical Excitation Energies

As an explanation of the stereochemistry of photoaddition between α,β-unsaturated carbonyl compounds and olefins, Wiesner suggested that the excited state of the α,β-unsaturated carbonyl compound is pyramidal at the β-carbon. It is shown by abinitio SCF and CI studies that for acrolein in the 1nπ*, 3nπ*, and 3ππ* excited states the β-carbon remains planar. In addition, vertical excitation energies for the 1nπ* and 1ππ*, and adiabatic excitation energies for the 1nπ* and 3nπ* states of trans-acrolein have been calculated.

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The electronic structure of the first row hydrides BH, CH, NH, OH and FH II. Excited states

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1959.0032 ◽

1959 ◽

Vol 249 (1258) ◽

pp. 402-413 ◽

Cited By ~ 32

Keyword(s):

Electronic Structure ◽

Excited States ◽

Electron Correlation ◽

Ground States ◽

Oscillator Strengths ◽

Excitation Energies ◽

Vertical Excitation ◽

Experimental Values ◽

Vertical Excitation Energies ◽

Dipole Length

Previous calculations on the ground states of the hydrides are extended to include the stable excited states. The ab initio orbital calculations predict vertical excitation energies which differ from the experimental values by as much as 2eV. However, when allowance is made for the effects of atomic electron correlation all errors in the calculated excitation energies become less than 0·2eV. The locations of excited states of different multiplicities from those of the ground states are predicted to within this accuracy. The oscillator strengths of allowed transitions from the ground states are calculated using both the dipole-length and dipole-velocity formulae. The dipole-length values are in fair agreement with the only experimental value available (for OH 2 ll → 2 ∑ + ), whereas the dipole-velocity values are much too large. Possible improvements in the accuracy of the calculations are discussed.

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