Excitation of the 6d 2D → 6p 2Po Radiative Transitions in the Pb+ Ion by Electron Impact

Results of experimental and theoretical investigation of electron-impact excitation of the 6s26d D2→6s26p P2o spectral transitions from the ground 6s26p P21/2o level in the Pb+ ion are presented. The experimental excitation functions for the transitions, measured by a VUV spectroscopy method, using the crossed electron and ion beams technique, reveal a rather distinct resonance structure resulting mainly from the electron decay of both atomic and ionic autoionizing states. The absolute values of the emission cross-sections, obtained by normalizing the experimental data at the incident electron energy 100 eV by those calculated using the Flexible Atomic Code software package, were found to be (0.35 ± 0.17) × 10–16 cm2 for the 6s26d D23/2 → 6s26p P21/2o (λ143.4 nm) transition and (0.19 ± 0.09) × 10–16 cm2 for the 6s26d D25/2 → 6s26p P23/2o (λ182.2 nm) transition.

Simultaneous Excitation of Helium by Means of an Electron and a Photon: A Joined Experimental and Theoretical Study

We report on a joined experimental and theoretical study of differential cross-sections resulting from inelastic scattering of a monoenergetic electron by helium atoms in the presence of an intense carbon dioxide laser. In particular, we measured the signals of the scattered electrons during the simultaneous electron–photon excitation of He 21P state for the first three microseconds of the laser pulse. The signals were measured for an incident electron energy of 45 eV and showed a structure that emerged at small scattering angles. The latter was found to be sensitive to the nature of the transferred photons, as well as the intensity of the laser field. The experimental findings were supported by quantum calculations based on the second-order Born approximation in which the correlated electron–electron interactions were taken into account.

Cross sections for the two-step radiative decay process $$X(v)\rightarrow A(v^{\prime \prime })\rightarrow X(v^\prime )$$ in e-LiH collisions

The cross sections for the two-step process, represented by the electron-impact vibro-electronic excitation $$X^1\varSigma ^+(v) \rightarrow A^1\varSigma ^+(v'')$$ X 1 Σ + ( v ) → A 1 Σ + ( v ′ ′ ) of the LiH molecule, followed by radiative decay back on the vibrational manifold of the ground state, $$A^1\varSigma ^+(v'')\rightarrow X^1\varSigma ^+(v')$$ A 1 Σ + ( v ′ ′ ) → X 1 Σ + ( v ′ ) , are calculated as a function of the incident electron energy from the threshold to 1000 eV. The final cross sections for the two-step process, which results in an overall vibrational excitation of the molecule, known also as E-v process, are provided for all the possible $$v,v'$$ v , v ′ transitions among the vibrational levels, including the continuum, of the electronic ground state. Graphic abstract

Structural and Secondary Electron Yield Properties of Titanium–Palladium Films with Laser-Treated Copper Substrate for Application in Neutron Generators

Secondary electron emission (SEE) of the oxygen-free high-conductivity copper (OFHC) target surface in neutron generators limits the stability and improvement of the neutron yield. A novel-type target of titanium–palladium films coated on laser-treated OFHC target substrate was proposed and explored in this work to obtain low secondary electron yield (SEY) without introducing any components. The combination of Ti–Pd films and laser-treated OFHC substrate can effectively suppress secondary electron emission and enhance the adsorption ability to hydrogen isotopes with the existence of Pd film. The surface morphologies, surface chemical states, and SEYs of Ti–Pd films with laser-treated OFHC substrate were studied systematically for the first time. The XPS results showed that the laser-treated OFHC substrate surface was basically covered by Pd film. However, the Pd film surface was partially oxidized, with percentages of 21.31 and 10.02% for PdO and PdO2, respectively. The SEYs of Ti–Pd films with laser-treated OFHC substrate were all below 1 within the investigated primary energy range of 100–3000 eV, which would be sufficient for application in neutron generators. Specifically, the maximum SEY (δmax) of laser-treated OFHC substrate coated by Ti–Pd films was 0.87 with corresponding incident electron energy of 400 eV.

Electron Irradiation Effects on the Optical and Electrical Properties of ZnO/Ag/SnO2 Thin Films

Transparent conductive ZnO 50 nm/Ag 10 nm/SnO₂ 50 nm (ZAS) tri-layer films were deposited on glass substrates by magnetron sputtering, and then the surface was subjected to intense electron beam irradiation to investigate the effects of electron irradiation on the structural, optical, and electrical properties of the films. After deposition, the ZAS thin films were electron-irradiated for 10 minutes, with varying electron incident energies of 300, 600, and 900 eV. The films that were electron irradiated at 900 eV showed higher optical transmittance of 83.6% in the visible wavelength region, and lower resistivity, of 4.75 × 10^-5 Ωcm, than the other films. From the observed electrical properties and optical band gap, it was concluded that the optical band gap increased with the incident electron energy up to 600 eV. The optical band gap increased from 4.12 to 4.23 eV, with carrier density increasing from 7.09 to 8.55 × 10²¹ cm⁻³. However, the film electron irradiated at 900 eV showed a decrease in optical band gap energy of 4.16 eV due to the decreased carrier density of 8.25 × 10²¹ cm⁻³. The figure of merit revealed that the ZAS thin films electron-irradiated at 900 eV had higher optical and electrical performance than the other films prepared in this study.

Electronic tunneling through a potential barrier on the surface of a topological insulator

We investigate the tunneling transport for electrons on the surface of a topological insulator (TI) through an electrostatic potential barrier. By using the Dirac equation with the continuity conditions for all segments of wave functions at the interfaces between regions inside and outside the barrier, we calculate analytically the transmission probability and conductance for the system. It is demonstrated that, the Klein paradox can also been observed in the system same as in graphene system. Interestingly, the conductance reaches the minimum value when the incident electron energy is equal to the barrier strength. Moreover, with increasing barrier width, the conductance turns up some tunneling oscillation peaks, and larger barrier strength can cause lower conductance, shorter period but larger oscillation amplitude. The oscillation amplitude decreases as the barrier width increases, which is similar as that of the system consisting of the compressive uniaxial strain applied on a TI, but somewhat different from that of graphene system where the oscillation amplitude is a constant. The findings here imply that an electrostatic barrier can greatly influence the electron tunneling transport of the system, and may provide a new way to realize directional filtering of electrons.