Spin-orbit vibronic coupling in polyatomic molecules

• Applicant: Professor Dr. Wolfgang Domcke
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2004 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5439408

• Final Report Year: 2011

Final Report Abstract

In this project, the theory of vibronic coupling in linear molecules has been extended through a systematic analysis of vibronic-coupling terms which arise from the spin-orbit (SO) operator. The SO coupling is described by the (essentially exact) Breit-Pauli operator, which can be derived from the Dirac-Coulomb-Hamiltonian in the so-called Pauli approximation. It has been shown that the Breit-Pauli operator gives rise to novel vibronic-coupling terms which are linear in the bending amplitude (in contrast to the well-known Renner effect, which is quadratic in the bending amplitude). The spectroscopic effects of the SO-induced linear vibronic-coupling term in isolated 2Π states have been investigated by numerical calculations of vibronic spectra for a number of examples, e.g. the X2Π photoelectron spectra of the halogen cyanides XCN, X = F, Cl, Br, and the X2Π state of GeCH. The theory has been extended to describe SO-induced vibronic coupling in 3Π states. The relevance of the SO-induced linear vibronic-coupling effects has been demonstrated for the A3Π states of the series CCX (X = O, S, Se) and CNY (Y = N, P, As). The Hamiltonian for the vibronic coupling of 2Π and 2Σ states via the bending mode (so-called Σ-Π coupling) has been developed, taking account of novel vibronic-coupling terms which arise from the Breit-Pauli operator. As an application of this theory, the vibronic structure of the photodetachment spectra of CCX (X = Cl, Br) have been calculated. Finally, the vibronic and SO-induced interactions among the 3Σ-, 1Δ and 1Σ+ electronic states arising from a half-filled π orbital in linear triatomic molecules have been analyzed, including terms up to fourth order in the bending amplitude. The spectroscopic effects of SO-induced vibronic couplings have been explored by extensive calculations of vibronic spectra for appropriate models.

Publications

• Spectroscopic effects of first-order relativistic vibronic coupling in linear triatomic molecules. J. Chem. Phys. 123, 124104 (2005)
  S. Mishra, V. Vallet, L.V. Poluyanov and W. Domcke
  
• Calculations of the vibronic structure of the photodetachment spectra of CCCl- and CCBr-. J. Chem. Phys. 125, 164327 (2006)
  S. Mishra, V. Vallet, L.V. Poluyanov and W. Domcke
  
• Calculations of the vibronic structure of the X2Π photoelectron spectra of XCN, X = F, Cl and Br. J. Chem. Phys. 124, 044317 (2006)
  S. Mishra, V. Vallet, L.V. Poluyanov and W. Domcke
  
• Importance of spin-orbit coupling for the assignment of the photodetachment spectra of AuX2- (X = Cl, Br and I). ChemPhysChem 7, 723 (2006)
  S. Mishra, V. Vallet and W. Domcke
  
• Study of strong Σ-Π and spin-orbit vibronic coupling effects in linear triatomic molecules. Chem. Phys. 327, 457 (2006)
  S. Mishra, W. Domcke and L.V. Poluyanov
  
• A study of spin-orbit vibronic-coupling effects in the A3Π state of CCX (X = O, S, Se) and CNY (Y = N, P, As). Chem. Phys. Lett. 446, 256 (2007)
  S. Mishra, W. Domcke and L. V. Poluyanov
  
• Spin-orbit vibronic coupling in 3Π states of linear triatomic molecules. J. Chem. Phys. 126, 134312 (2007)
  S. Mishra, L.V. Poluyanov and W. Domcke
  
• Renner-Teller and spin-orbit vibronic coupling effects in linear triatomic molecules with a half-filled π shell. J. Chem. Phys. 128, 124318 (2008)
  I. Sioutis, S. Mishra, L. V. Poluyanov and W. Domcke