Potential-energy surface, van der Waals energy spectrum, and vibronic transitions in s-tetrazine-argon complex -: art. no. 044310

The van der Waals vibrational states and the structure of the vibronic spectrum of s-tetrazine-argon complex have been studied by the ab initio methods. The potential-energy surface of the ground S-0 electronic state of the complex has been constructed by fitting the analytical many-body expansion to a large set of the interaction energy values computed using the second-order Moller-Plesset perturbation theory combined with the standard aug-cc-pVDZ basis set. The equilibrium structure of the complex found is that with argon located above the tetrazine ring at a distance of 3.394 A. The calculated dissociation energy of 354 cm(-1) is compatible with the experiment. The van der Waals energy spectrum calculated from the potential-energy surface is explained analyzing a correlation with a simpler energy spectrum of benzene-argon. A new assignment of the S-0-S-1 vibronic spectrum is proposed on the basis of the rigorous selection rules, vibrational energy levels in S-0 and S-1 states and vibronic transition intensities calculated from the electronic transition dipole moment surfaces. (c) 2006 American Institute of Physics.