Theoretical study of the electronic spectra of cyclopentadiene, pyrrole, and furan
| Autor: | Bjoern O. Roos, Ignacio Nebot-Gil, Luis Serrano-Andrés, Manuela Merchán, Markus P. Fülscher |
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| Rok vydání: | 1993 |
| Předmět: |
Valence (chemistry)
Electronic correlation Chemistry General Chemistry Biochemistry Molecular physics Catalysis Molecular electronic transition Spectral line symbols.namesake Colloid and Surface Chemistry Computational chemistry Ab initio quantum chemistry methods Excited state Rydberg formula symbols Rydberg state |
| Zdroj: | Journal of the American Chemical Society. 115:6184-6197 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The electronic spectra of the title molecules have been studied using a newly proposed quantum chemical approach for ab initio calculations of dynamic electron correlation effects in molecular systems: multiconfigurational second-order perturbation theory (CASPT2). For cyclopentadiene and furan, the calculations comprise three valence excited singlet states and, in addition, the la2 - 3s, 3p, and 3d Rydberg states, thus providing a full assignment of the spectra in the energy range below 8.0 eV. For pyrrole, the 2bl - 3s. 3p, and 3d components of the Rydberg series have been added. The four lowest triplet states have also been studied in all three molecules. The computed excitation energies deviate from experiment by less than 0.17 eV in all cases where an assignment is possible. It is shown that the two main features in the spectra are caused by the valence excited states 1Bz (5.27, 5.92,6.04 eV) and 'A: (7.89, 7.46, 7.74 eV), where the calculated energies for the two states in the three molecules are given in parentheses. In addition, the 'A; state has been determined to appear near 6 eV in all three molecules. These results differ drastically from earlier theoretical predictions but are in agreement with experimental data. A number of new assignments of the Rydberg states are suggested. |
| Databáze: | OpenAIRE |
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