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Roberto Linguerri, Najia Komiha, Jürgen Fabian, Pavel Rosmus

Electronic States of the Ultramarine Chromophore S₃^-

Keywords: Thiozonide, Ozonide, UV Spectra, Spin-Orbit Coupling, IR Transitions

The potential energy surfaces and the spin–orbit couplings for states correlating with the lowest dissociation asymptote S₂(X³Σ^-_g) + S^-(²P) of the radical anion of thiozone have been calculated by full valence complete active space self-consistent field (CASSCF), internally contracted multi-reference configuration interaction (IC-MRCI) and for some of the states also by restricted coupled cluster with perturbative triples (RCCSD(T)) ab initio methods. For six electronic states lying below the electron detachment threshold: X²B₁, A²B₂, B²A₁, C²A₂, ⁴Σ_g^-, and the second ²A₁, equilibrium geometries and harmonic wavenumbers are reported. For the ground state also anharmonic vibrational levels have been evaluated. Due to the intensity borrowing via vibronic coupling with the B²A₁ state also the dipole forbidden A–X transition becomes allowed in the Franck–Condon region of the UV spectrum. The C²A₂ state responsible for the blue color of ultramarine correlates adiabatically with the first dissociation asymptote S₂(X³Σ^-_g) + S^-(²P). Along the dissociation path the regions of vibronic and spin–orbit couplings were located. For the R_{S2 - S} larger than about 2.6Å the electron spin-states of the lowest dissociation asymptote are strongly mixed. The properties of the S₃^- electronic states are compared with those of O₃^-.

Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0942-9352
Volume: 222, 01/2008
Pages: 163 - 176

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