Autoionization from the plasmon resonance in isolated 1-cyanonaphthalene

Photoionization of Nitrile-substituted Naphthalene and Benzene: Cation Spectroscopy, Photostability, and Implications for Photoelectric Gas Heating

“…The simulated D 1 [1A″] X + ←S 0 X band shown in Figure 3(a) is shifted by −88 meV to match the experimental 0-0 origin band, which is not unexpected at this level of theory. It is dominated by the adiabatic transition, which is measured at 8.610 ± 0.005 eV, in good agreement with the AIE of 8.6127 ± 0.0006 eV reported by Shivatare et al (2013) using the two-color resonant MATI technique, the recent synchrotronbased photoelectron spectroscopy work by Bull et al (2023), which gave a value of 8.60 ± 0.03 eV, and with the two earlier works on He I PES quoting the ionization potential at 8.61 eV (Utsunomiya et al 1975) and 8.59 eV (Klasinc et al 1983; see Table A1 in the Appendix). From the simulations, it is inferred that the band around 8.77 eV corresponds to the in-plane ring deformation and the strong bands around 8.88 and 9.07 eV are due to the CC and CH stretching, respectively, whereas the band at 8.97 eV is a result of the C-CN stretching mode.…”

“…An overall very good agreement is observed for the three highest molecular orbitals followed by a qualitative agreement for the others. The second and third bands at 9.37 and 10.3 eV match well with the photoelectron spectrum of Bull et al (2023), which are assigned to D 1 [2A″] A + ← S 0 X transition and D 2 [3A″] B + ← S 0 X transition, respectively. The clear vibronic structure seen experimentally in the B band (second excited electronic state) allows us to report an accurate value for the third ionization energy, 10.294 ± 0.005 eV.…”

“…This work 8.610 ± 0.005 Bull et al (2023) 8.60 ± 0.03 Shivatare et al (2013) 8.6127 ± 0.0006 Klasinc et al (1983) 8.59 Utsunomiya et al (1975) 8.61 This work 9.736 ± 0.005 Kwon et al (2003) 9.7288 ± 0.0006 Araki et al (1996) 9.7315 ± 0.0002…”

“…Having a closer look at the 2D matrix, one can clearly see an increase in signal intensity on the third and fourth excited states over a broad energy range between 15.2 and 18 eV photon energy with the electron kinetic energy (KE) varying from 3.2 to 5 eV. According to the description of Bull et al (2023), when 1-CNN is subjected to VUV radiation, particularly in the range of 11.5 and 16 eV, the molecule is photoexcited to the plasmon resonance, which then undergoes autoionization. Plasmon resonances occur due to a collective excitation of valence electrons to π * states and are observed frequently in fullerene, graphene, and isolated PAHs.…”

“…The cationic spectra of 1-CNN were recorded by ionizing via the 0 0 , 33 1 , 32 1 , and 31 1 intermediate vibronic levels in the S 1 state of the neutral, providing the precise ionization energy of 1-CNN. Very recently, Bull et al (2023) have reported on the photoionization dynamics of 1-CNN using synchrotron radiation, emphasizing that direct ionization is less probable compared to plasmon excitation followed by autoionization, where, upon absorption of the VUV photons, the molecule is photoexcited to the plasmon resonance, dominated by π-π * transitions, which then undergoes prompt autoionization. Along with showing the photoelectron spectra, the authors have obtained the anisotropy parameter (β 2 ), further testified by scattering calculations.…”