Showing papers by "Vincent Boudon published in 2001"

Rotational-vibrational relative equilibria and the structure of quantum energy spectrum of the tetrahedral molecule P4

Abstract: We find relative equilibria (RE) of the rotating and vibrating tetrahedral molecule P4 and study the correspondence of these RE's to the extremal quantum states in the vibration-rotation multiplet and to the extrema of the semi-quantum rotational energy surfaces obtained for a number of excited vibrational states. To compute the energy of RE's we normalize the full rotation-vibration Hamiltonian H of P4 in the approximation of nonresonant modes ν E 2 and ν F_2 3 and find the stationary points of the resulting normal form (known as reduced effective Hamiltonian H eff ) which is defined on the reduced phase space CP 2 × CP 1 × S 2 . Most of these points are fixed points of the symmetry group action on CP 2 × CP 1 × S 2 . To explain our results in more detail we introduce numerical values of the parameters of H, such as the cubic force constants, using an atom-atom harmonic potential with one adjustable parameter. This simple model gives correct qualitative description of the rotational structure of the lowest excited vibrational states ν 2 , ν 3 and ν 2 + ν 3 of P4.

The spectrum of an octahedral molecule in a degenerate electronic state: The ν6 fundamental band of jet-cooled V(CO)6

Abstract: The jet-cooled FTIR spectrum of the ν6 fundamental band (C–O stretch) of vanadium hexacarbonyl, V(CO)6, is studied for the first time. The spectrum shows a very unusual structure consisting of three well-defined broad subbands, without the usual PQR structure. V(CO)6 being an open-shell system this is attributed to a dynamical F2g⊗F1u Jahn–Teller coupling which considerably complicates the analysis. A new theoretical model based on group theory and tensorial algebraic techniques is developed in this paper for the very first attempt to analyze such a rovibronic spectrum. The assumption of a negligible spin–orbit coupling is validated by the overall agreement between predicted and observed band profiles. The rovibronic Hamiltonian and dipole moment operators have been expanded in order to enable a simultaneous treatment of the four vibronic sublevels. We were able to satisfactorily reproduce the band profile and thus to give the first estimation of some rovibronic parameters for this molecule.