A MS-CASPT2 study of the low-lying electronic excited states of CH2BrCl |
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| Institution: | 1. Institut für Optik und Quantenelektronik, Max-Wien-Platz 1, D-07743 Jena, Germany;2. Institut für Chemie, Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany;1. Dipartimento di Scienze della Terra, Università degli Studi di Torino, via Valperga Caluso 35, 10125 Torino, Italy;2. Alpine Palaeomagnetic Laboratory, via Luigi Massa 4, 12016 Peveragno, Italy;3. Earth and Environmental Sciences Section, Université de Genève, Rue des Maraîchers 13, 1205 Genève, Switzerland;4. Laboratoire de Paléomagnétisme, Musée de Préhistoire des gorges du Verdon, 04500 Quinson, France;5. Facultad de CC. Físicas, Dpto. de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, Avd. Complutense s/n, 28040-Madrid, Spain;6. Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy;7. Archaeology Program, Lycoming College, One College Place, Williamsport, PA 17701, USA;8. Department of Antiquities, 1 Museum Avenue, Nicosia 1097, Cyprus;9. Department of Classics, Davidson College, Davidson, NC 28035, USA;10. Department of Archaeology and History, La Trobe University, Melbourne Campus, Bundoora, 3086, VIC, Australia |
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| Abstract: | The low-lying singlet excited states of CH2BrCl have been calculated using multiconfigurational CASSCF, second-order perturbation theory CASPT2 and its multistate extension MS-CASPT2. The CASSCF method shows spurious valence–Rydberg mixing and a wrong order of states. Inclusion of dynamical correlation by single root CASPT2 lowers dramatically the energy of the valences states but does not lead to a complete separation between valence and Rydberg states. This situation is improved by the MS-CASPT2 calculations, which gives two valence states for both A′ and A″ symmetries below the lowest Rydberg state, corresponding to n(Br)→σ*(C–Br) and n(Cl)→σ*(C–Cl) transitions at 6.1 eV (203 nm) and 7.2 eV (173 nm), and being repulsive along C–Br and C–Cl coordinates. |
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