van der Waals bond stretch and bend frequencies in the molecules tetrazine–X (X=Xe, Kr, and Ar)

Abstract

Fluorescence excitation and dispersed fluorescence spectra of the clusters s-tetrazine–X (X=Xe, Kr, Ar) have been studied to determine the van der Waals bond stretch and bend frequencies. In the case of tetrazine–Xe a vibrational progression spanning v=0 to 8 in the bend vibrations was detected. The harmonic frequencies of the van der Waals bond stretch and bond bend vibrations are found to be very similar for the T–Xe, T–Kr, and T–Ar clusters. Spectra of the symmetric trimer xenon–tetrazine–xenon show progressions in the van der Waals bond stretch vibration up to v″=5. The frequencies of the stretch vibration in tetrazine–xenon and the symetric stretch vibration in xenon–tetrazine–xenon support the validity of pairwise additivity of the van der Waals potentials. The excitation spectra also indicate the prescence of other, more complicated, clusters of tetrazine with xenon.