Low energy electron impact excitation spectra of 1,3,5-cycloheptatriene and 1,3,5,7-cyclo-octatetraene

The electronically excited states of cyclooctatetraene—An analysis of the vacuum ultraviolet absorption spectrum by ab initio configuration interaction methods

“…4, is confirmed by EI studies. 21,22 The present MRD-CI calculations show that a closely spaced pair of 1 B 1 and 1 B 2 states with similar f(r) occurs in this energy range. We combine these as 1 E, given the similar MOs involved, which leads to a more probable assignment than a 1 A 2 state, 21,22 which can only appear via vibronic coupling.…”

“…40 Overall only one band, near 4 eV, is common to these EI studies. 21,22 The present calculations in SM1 and SM4 show several vertical states occur below 5.5 eV; several of these have zero f(r) although not optically forbidden by symmetry.…”

“…Comparison with the electron impact (EI) profile, in Fig. 4 for the energy range up to 11 eV, 21,22 shows considerable similarities; this is to be expected for EI using a high beam energy with a low scattering angle. The clear peak at 4.43 eV in the EI profile 21 confirms the very weak UV absorption observed there.…”

“…Three triplet states near 3.05, 4.05, and 4.84 eV, observed by Frueholz and Kuppermann, 21 have an apparent vibrational structure. In contrast, the spectrum of Knoop et al 22 apparently shows a weak structure on a single broad peak covering the range 3.4-4.1 eV. There is no apparent identification of a COT triplet state, showing an absorption maximum at 3.542 eV (350 nm), which was observed using a linear electron accelerator.…”

“…The principal aim of this paper is to present and interpret the VUV spectrum in contemporary terms and compare with electron impact (EI) spectra. 21,22 It is a major upgrade to an early configuration interaction (CI) study of the excited and ionized states of COT 23 and will entail determination of the equilibrium structures for several electronic states in a rigid structural framework. A Rydberg state analysis links results from both this study and our reinvestigation of the photoelectron (PES) spectrum of COT.…”