Mass spectra of negative ions of condensed aromatic hydrocarbons and biphenyl

Negative ions, molecular electron affinity and orbital structure of cata‐condensed polycyclic aromatic hydrocarbons

“… †Our τ а value for anthracene is in fairly good agreement with the earlier values, 21 μs and 25 μs, which were measured using an analogous experimental technique to that in this work. For phenanthrene observation of [M] •− ions with exactly the same τ а as for anthracene has been reported .…”

“…This enabled the vertical detachment energy to be measured using photodetachment spectroscopy and the phenanthrene adiabatic EA was assigned as 0.12 eV. In addition, based on the successful detection of long‐lived phenanthrene [M] •− ions, one may conjecture that the latter were not detected earlier in electron‐beam experiments because the temperature of the sample vapor was too high. The high internal energy of [M] •− ions and the low EA values (i.e.…”

“…By mass spectrometric experiments using resonance electron capture, it has been shown that linearly condensed three‐ring molecules of anthracene effectively attach electrons of thermal energy (0 < E e < k⋅T ) thereby forming long‐lived molecular negative ions (MNIs), whose mean lifetimes with respect to electron autodetachment ( τ а ) have been measured as 41 μs . The MNI for the angular isomer, phenanthrene, has not, however, been detected evidently because its lifetime is too short for mass spectrometric detection ( τ а < 1 μs). Analogously, we have found no MNI peak in the mass spectra of triphenylene, the star‐like branched molecule bearing one more benzenoid ring (isomer of tetracene).…”

Low-Energy Electron Irradiation Damage in Few-Monolayer Pentacene Films

“…In another similar mass spectroscopic study, singly charged anions of pentacene molecules with one hydrogen missing were detected starting from ∼5 up to ∼11 eV, with much smaller quantities (about 100 times lower) found in the range 3–5 eV. Singly charged negative anions of other polycyclic aromatic hydrocarbons with one hydrogen missing were also detected in several other studies, , showing a distribution centered around 8 eV and becoming increasingly smaller above 10 eV and below 6 eV. In a study of vibrational states of gaseous benzene molecules probed with incident electrons, the cross section for excitation of the carbon–hydrogen bond is shown to have a resonance between 5.5 and 10 eV, with a peak at 8 eV, accompanied by a smaller resonance between 4 and 5.5 eV .…”