Mechanisms producing inelastic structures in low-energy electron transmission spectra

Interactions of Low-Energy Electrons with Atomic and Molecular Solids

“…In other words, are the peaks 2-3 eV above threshold in Figures 17 and 18 resonances? Author: From our data on threshold electronic excitation of N 2 and CO [87,88) which resemble the gasphase results, I would say, yes; resonances are also important to create bulk and surface excitons. The peaks in Figures 17 and 18 could derive from broad resonances but this would be difficult to prove.…”

“…Non-dissociative electronic excitation by low-energy electrons in multilayer atomic and molecular films has been investigated by LEET [5,14,40,41,52,53,54,55,78,87,88,160,177,178,187] and HREEL spectroscopies [6, 19, 88, 97, 103, 106, ll 1, ll6, 143, 166, 168, 171, 190, 191, 192, 193, 194] and, more recently, by ESD and UV detection techniques [4,80,81,84,85,86]. The excitation of electronic states of atoms and non-dissociative electronic states of molecules in dielectrics can result in localized energy depositions [166,193] or into the formation of excitons [103] moving within the solid with a well-defined wave vector.…”

Early Events in Radiobiology: Isolated and Cluster DNA Damage Induced by Initial Cations and Nonionizing Secondary Electrons

“…Figure shows the absolute value of the current passing through 5 ML films of plasmid DNA disorderly lyophilized on graphite and tantalum , or uniformly deposited parallel to a tantalum surface by intercalating diaminopropane (DAP) between the DNA molecules. , Details of the experiments are given in the Supporting Information. It is important to note that in transmission experiments the current is the same, whether charges are retained in the film or reach the substrate. , As seen from Figure , above 30 eV the current transmitted to the substrate changes sign; thus, ionization (i.e., positive hole formation) starts to dominate the total inelastic scattering cross section (CS). At 100 eV, this hole-dominated current is about 3.5 larger than the maximum electron current transmitted around 10 eV, showing qualitatively that the films are highly ionized.…”

“…This finding is compatible with hole-hopping and electron-transfer distances being shorter than 10 nm in irradiated DNA. − Thus, the latter value and the curves of Figure indicate that holes are expected to be trapped in our films. Consequently, the large difference between curve A of Figure and the others (curves B–D) result essentially from electron scattering from DNA molecules and the transmission coefficients of electrons coming in and out of the film at the vacuum interface . , The transmission method and the underlying phenomena have been amply explained in the literature. ,, A more quantitative analysis of the transmission curves of Figure is possible by estimating electron transmission and reflection coefficients at the vacuum interface and the band structure of the DNA film (Supporting Information). ,, As shown in the Supporting Information, positive hole currents are 3.4 and 4.5 larger than the incident electron current at 60 and 100 eV, respectively (i.e., for every electron entering the film there are 3.4 and 4.5 holes created, which corresponds to 6.8 and 9 ionizations per plasmid, respectively).…”

“…Consequently, the large difference between curve A of Figure and the others (curves B–D) result essentially from electron scattering from DNA molecules and the transmission coefficients of electrons coming in and out of the film at the vacuum interface . , The transmission method and the underlying phenomena have been amply explained in the literature. ,, A more quantitative analysis of the transmission curves of Figure is possible by estimating electron transmission and reflection coefficients at the vacuum interface and the band structure of the DNA film (Supporting Information). ,, As shown in the Supporting Information, positive hole currents are 3.4 and 4.5 larger than the incident electron current at 60 and 100 eV, respectively (i.e., for every electron entering the film there are 3.4 and 4.5 holes created, which corresponds to 6.8 and 9 ionizations per plasmid, respectively). This simple transmission measurement indicates that most holes (i.e., cations) are trapped and do not recombine with electrons in our films, within the time scale (50 ms) of the measurements (Supporting Information).…”