High resolution electron impact studies of electric dipole-forbidden states of benzene

Forward Electron Scattering in Benzene; Forbidden Transitions and Excitation Functions

“…At low residual energies the spectrum is dominated by the three lowest triplet transitions in the regions 1, 2 and 3. The present low-energy (0-2 eV) forward-scattering spectra are very similar to the spectra obtained previously with intermediate (10 eV) residual energies and large scattering angles in both gaseous [4] and solid [19] phases. At 20 eV the relative intensity of the triplet states has dropped drastically and the spectrum is nearly identical to an optical absorption spectrum such as given in [ 5 ] both in relative intensities of the electronic transitions and the envelopes of the individual bands.…”

“…The broad feature was not previously reported and could also correspond to the missing 'EZg transition. Detailed comparison of the present spectra with those of Wilden & Comer [4] reveal that they are consistent and the only differences stem from different relative intensities of the features under different scattering conditions. The present spectra with residual energies of 0.03 and 0.1 eV are similar to the residual energy spectrum at 60" and 10 eV of Wilden & Comer except that the improved visibility of the 3E2g state in the present study permits the location of the origin one vibrational level lower and the identification of two vibrational progressions.…”

“…The present spectra with residual energies of 0.5 and 0.7 eV are similar to the 10" to 40"-spectra of Wilden & Comer. The 6.33 eV (6.32 eV in [4]) peak is present in both cases but the 6.28 eV peak is visible only under the conditions of the present experiment.…”

“…The observed splitting of 0.05 eV is in excellent agreement with this expectation. Finally a band has been observed by Wilden & Comer [4] at 7.81 eV. Bolovinos et al [ 5 ] suggested an assignment to a 4s-band with 6=0.92.…”

“…The observation was later confirmed by Doering [3]. Wilden & Comer [4] investigated this region with better resolution at a number of scattering angles and a residual energy of 10 eV. They discovered a new progression at a large angle (60") and assigned it to the 3E2, state expected in this energy region.…”