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RESEARCH PRODUCT
Theoretical characterization of the lowest-energy absorption band of pyrrole
Per-åke MalmqvistLuis Serrano-andrésManuela MerchánVincent MolinaBjörn O. Roossubject
Valence (chemistry)Organic compounds ; Vibrational states ; Perturbation theory ; Rydberg states ; Orbital calculationsAb initioGeneral Physics and AstronomyPerturbation theoryRydberg statesUNESCO::FÍSICA::Química físicaOrbital calculationschemistry.chemical_compoundsymbols.namesakechemistryEnergy absorptionAtomic electron transitionExcited stateOrganic compoundsRydberg formulasymbolsTheoretical chemistryVibrational statesPhysical and Theoretical ChemistryAtomic physics:FÍSICA::Química física [UNESCO]Pyrroledescription
The lowest-energy band of the electronic spectrum of pyrrole has been studied with vibrational resolution by using multiconfigurational second-order perturbation theory (CASPT2) and its multistate extension (MS–CASPT2) in conjunction with large atomic natural orbital-type basis sets including Rydberg functions. The obtained results provide a consistent picture of the recorded spectrum in the energy region 5.5–6.5 eV and confirm that the bulk of the intensity of the band arises from a ππ∗ intravalence transition, in contradiction to recent theoretical claims. Computed band origins for the 3s,3p Rydberg electronic transitions are in agreement with the available experimental data, although new assignments are suggested. As illustrated in the paper, the proper treatment of the valence–Rydberg mixing is particularly challenging for ab initio methodologies and can be seen as the main source of deviation among the recent theoretical results as regards the position of the low-lying valence excited states of pyrrole. serrano@uv.es ; merchan@uv.es
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2002-05-01 |