Erratum to: Excitons in ZnO Quantum Wells

Physics of the Solid State - The name of the fifth author should read Mohrain.     

Molecular Structure of Chloral (CCl3CHO) in the Lowest Excited Singlet State

The structure and the conformational behavior of the chloral CCl₃CHO molecule in the lowest excited singlet state (S₁) was investigated by CASSCF and CI ab initio quantum-chemical methods. It is shown that electronic excitation S₁S₀ causes significant changes in the molecular structure, namely, CCl₃ top rotation and pyramidalization of the carbonyl (CCHO) fragment. A relationship between the torsional and inversion vibrations of chloral in the S₁ state has been found. For large-amplitude nuclear motions corresponding to the torsional and inversion vibrations, the corresponding one- and two-dimensional problems were solved. The results are compared with the experimental data and with the results of previous calculations for the lowest excited triplet (T₁) state.     

Quantum-chemical study of the structure of the acetyl fluoride molecule in the ground and lowest excited singlet and triplet electronic states

The structure of the conformationally flexible acetyl fluoride molecule (CH3CFO and CD3CFO) in the ground (S0) and lowest excited triplet (T1) and singlet (S1) electronic states was calculated by different quantum-chemical methods (RHF, UHF, MP2, CASSCF). The equilibrium geometric parameters and harmonic vibrational frequencies of the molecules in these electronic states were estimated. The calculations demonstrated that the electronic excitation causes considerable conformational changes involving the rotation of the CH3(CD3) top and a substantial deviation of the CCFO carbonyl fragment from planarity. For large-amplitude vibrations, namely, for the torsional vibration in the S0 state and the torsional and inversion (nonplanar carbonyl fragment) vibrations in the T1 and S1 states, the quantum-mechanical problems were solved in one-dimensional (1D) and two-dimensional (2D) approximations. The results of calculations are in good agreement with experimental data.     

Theoretical study of the structure of the CClF2NO and CCl2FNO molecules in the ground and lowest excited singlet and triplet electronic states

The potential energy surfaces of the nitroso compounds CClF₂NO and CCl₂FNO in the ground and lowest excited singlet and triplet electronic states were studied by various ab initio methods (including multiconfigurational methods). The equilibrium geometric parameters, vibrational frequencies, internal rotation potential functions, and rotational contours of bands in the S₁ S₀ vibronic spectrum of the CClF₂NO molecule were calculated. For the molecules under consideration, the quantum-mechanical problem on torsional motion was solved. The results of calculations are, on the whole, in good agreement with experiment.     

Ab initio study of torsional vibrations of the fluoral molecule in the ground state

A comparative analysis of various approximations used to solve the problem on the torsional motion of the CF₃ group in the trifluoroacetaldehyde molecule is presented. It is considered how the estimates of torsional transition frequencies are affected by the choice of a basis set for an ab initio calculation, by the method of inclusion of electron correlation, by the geometrical model of the molecule, and by the method of determination of nuclear energy levels. The results are also considered for the related acetaldehyde molecule. The Appendix briefly defines the structure of the energy levels of torsional symmetric top vibrations. M. V. Lomonosov Moscow State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 3, pp. 514–521, May–June, 1998.     

One- and Two-Dimensional Torsion-Inversion Models for the Fluoral Molecule (CF3CHO) in Excited Electronic States

The structure of the conformationally nonrigid fluoral molecule (CF₃CHO) in the ground (S₀) and lowest excited triplet (T₁) and singlet (S₁) electronic states was studied by ab initio quantum-chemical methods. The equilibrium geometric parameters and harmonic vibrational frequencies of the molecule in these electronic states were determined. The calculations demonstrated that the electronic excitation causes substantial changes in the molecular structure involving the rotation of the CF₃ top and the deviation of the CCHO carbonyl fragment from planarity. The quantum-mechanical problems for large-amplitude vibrations, namely, for the torsional vibration in the S₀ state and the torsional and inversion vibrations (nonplanar carbonyl fragment) in the T₁ and S₁ states, were solved in the one- and two-dimensional approximations. A comparison of the results of calculations revealed the correlation between the torsional and inversion motions.