Photoelectron spectra of the excited states of an intermediate case molecule: Pyrazine

The photoelectron spectrum for the mixed singlet–triplet levels populated through excitation of the origin of the S11B3u state in the intermediate case molecule pyrazine contains structure identifiable with the different spin components of the molecular eigenstates. The triplet part of the spectrum has a broad background and a few resolved peaks. It is suggested that the structured component is comprised of the transitions of a few high frequency vibrational combinations in the triplet, while the broad distribution of electron energies results from ionization of a dense manifold of low frequency combinations which are likely to undergo IVR. We also report the photoelectron spectrum of ‘‘relaxed’’ triplet states produced by collisional relaxation from levels populated after ISC from the origin of the S1 state.