Extended virial theorem applied to predissociation phenomena. Interpretation of the nearly degenerate G1Π ∼ I1Π energy spectra in SiO

The extended virial theorem, obtained from a Fourier–Laplace transformation of equations of motion, is applied to the phenomenon of predissociation. The underlying resonance energy model rigorously defined by means of the theory of dilation analytic operators prescribes in detail the balance between the various energy contributions in a way analogous to the situation prevailing in a stationary system. The extended virial theorem is applied to predissociation, particularly in connection with the interpretation of the nearly degenerate G1Π ∼ I1Π energy spectrum in SiO. It was previously found for the rovibronic spectra assigned to G1Π – X1Σ+ and I1Π – X1 Σ+, that every G – X band is accompanied by a I – X band. Whereas the I1Π state does not seem to undergo predissociation, the G state shows increasing predissociation with increasing vibrational quantum number. We show that the virial theorem generalized to include continuum phenomena offers an interpretation of the nearly degenerate spectra of SiO as well as of the concomitant isotope shift of SiO16 and SiO18 with respect to both resonance positions and widths.