Excitation of resonance lines of a Zn+ ion by electron impact

Excitation of individual components of the resonance 4p ² P ₁ ^2,3/2/0 doublet of a Zn⁺ ion by electron impact is studied for the first time by the spectroscopic method in crossed beams. A distinct structure (above the ionization potential of an ion as well) found in the energy dependences of the effective excitation cross section is associated mainly with the decay to the resonance levels (direct or cascade) of autoionization states of zinc atoms and ions formed through the excitation of electrons from the subvalence 3d ¹⁰ shell. The results obtained are compared with data of other experiments and theoretical calculations by the method of strong coupling of five and fifteen states, as well as with the semiempirical calculation using the Van Regemorter formula.     

Excitation cross-sections of erbium-atom resonance lines

Moscow Power Institute, 14, Krasnokazarmennaya Str., E-250, Moscow, 105835. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 63, No. 6, pp. 883–888, November–December, 1996.     

Excitation of resonance transitions in a thulium atom by slow electrons

We experimentally studied the excitation of resonance transitions in a thulium atom in electron-atom collisions. At an electron energy of 50 eV, we measured 52 TmI excitation cross sections. We recorded 41 optical excitation functions in the electron energy range from the excitation threshold to 200 eV. The measured cross sections are, on average, a factor of 1.09 larger than their preceding experimental values but a factor of 2.41 smaller than their theoretical values.     

Field emission of monoenergetic spin-polarized electrons

Field emission from a tungsten tip, covered by a layer of crystallized ferromagnetic europium sulfide, leads to an electron beam with a current of 10⁻⁸ A, an energy width of less than 100 meV, and a spin polarization of about 0.85 at a tip temperature of 9 K. Proper annealing of the EuS layer is crucial.     

Excitation of adenine molecules by slow electrons

The excitation of adenine molecules in the gas phase by slow electrons is studied by optical spectroscopy. The emission spectra of the molecule in the region of 250–500 nm upon excitation by slow electrons in the energy range of 15–120 eV, as well as the optical excitation functions of the most intense emission bands, are presented.     

Attenuation length of monoenergetic electrons photoinjected into the NaCl layer

A new, precise photoelectric method of electron attenuation length measurement in alkali halides is proposed and experimentally verified. The obtained results confirm the Llacer-Garwin theory of electron-phonon interactions in these substances.     

Excitation of the Na 3p state by monochromatized electrons

The relative differential cross section for the electron impact excitation of the unresolved sodium D lines was measured with a monochromatized electron beam.     

Excitation of quintet levels of the ytterbium atom by slow electrons

The excitation of transitions from upper quintet levels of the ytterbium atom is studied by the method of extended crossing beams. Seventy-five cross sections are measured at the excitation electron energy of 50 eV. Twelve optical excitation functions are recorded in the electron energy range from 0 to 200 eV.     

Elastic scattering of low-energy electrons by cadmium atoms

Experimental results on the differential cross sections of 180° elastic electron scattering and the total cross section of electron scattering by cadmium atoms in the energy range 0–6 eV are reported for the first time. Distinct shape resonances with the (5s ²5p)² P ⁰ and 5s5p ² configurations are revealed in the near-threshold range and at E≈4 eV. In the range 3.0–3.7 eV, the differential cross section exhibits extra singularities that are probably related to the d-wave shape resonance. The resonance contribution to the backscattering cross section near 4 eV is found to be about 20%.     

Excitation cross section for iridium atoms by slow electrons

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 711–716, May, 1991.     

Excitation of lowest electronic states of thymine by slow electrons

Excitation of lowest electronic states of the thymine molecules in the gas phase is studied by elec- tron energy loss spectroscopy. In addition to dipole-allowed transitions to singlet states, transitions to the lowest triplet states were observed. The low-energy features of the spectrum at 3.66 and 4.61 eV are identified with the excitation of the first triplet states 1₃ A′ (π → π*) and 1₃ A″ (n → π*). The higher-lying features at 4.96, 5.75, 6.17, and 7.35 eV are assigned mainly to the excitation of the π → π* transitions to the singlet states of the molecule. The excitation dynamics of the lowest states is studied. It is found that the first triplet state 1³ A′(π → π*) is most efficiently excited at a residual energy close to zero, while the singlet 2₁ A′(π → π*) state is excited with almost identical efficiency at different residual energies.     

Excitation of surface plasmons by electrons in a parabolic beam

A theory is presented for the excitation of surface plasmons by an electron beam following a non-touching path above a metal surface in Born approximation. The metal is assumed to possess only surface plasmon excitations. Configurations involving deflection of the electron beam in a parallel plate condensor, and by scattering from a field emission tip are envisaged. The relation between experimental conditions and the validity of the semiclassical approximation is discussed. The region of space above the surface in which scattering occurs is calculated, but the feasability of the experiment depends on electron optical factors which are outlined.     

Excitation of lowest electronic states of the uracil molecule by slow electrons

The excitation of lowest electronic states of the uracil molecule in the gas phase has been studied by electron energy loss spectroscopy. Along with excitation of lowest singlet states, excitation of two lowest triplet states at 3.75 and 4.76 eV (±0.05 eV) and vibrational excitation of the molecule in two resonant ranges (1?C2 and 3?C4 eV) have been observed for the first time. The peak of the excitation band related to the lowest singlet state (5.50 eV) is found to be blueshifted by 0.4 eV in comparison with the optical absorption spectroscopy data. The threshold excitation spectra have been measured for the first time, with detection of electrons inelastically scattered by an angle of 180°. These spectra exhibit clear separation of the 5.50-eV-wide band into two bands, which are due to the excitation of the triplet 1³ A?? and singlet 1¹ A?? states.     

Excitation of acoustic waves in metals by electrons and protons

A study of the excitation of acoustic oscillations in metals by electrons and protons is described. For thin metal plates, the amplitude of the electric signal is independant of the energy of the electrons and is proportional to the ionization losses of the charged particles. The dependence of the amplitude of the acoustic signal on the energy of the incident electrons and protons is considered and a comparison between the Cherenkov radiation, thermoelastic, and dynamic models is made.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 72–76, October, 1973.The authors thank I. A. Grishaev, I. I. Zalyubovskii, V. V. Petrenko, M. F. Lomanov, L. L. Gol'din, and Ya. L. Kleinbok for constant help in carrying out this work and to V. T. Lazurik-Él'tsufin for useful discussions.     

Elastic scattering of electrons and positrons by cadmium atoms

ABSTRACT

The differential, integrated elastic, total and momentum transfer cross sections along with Sherman function for the elastic scattering of electrons and positrons by cadmium atoms have been evaluated from the partial wave solution of the Dirac relativistic scattering equations for a projectile-atom complex potential at the energy range 6.4 eV < E < 1.0 keV. For various scattering quantities, a comparison of our results exhibits better agreement with the experimental data than the other available theoretical values.     

Tomography of injection and acceleration of monoenergetic electrons in a laser-wakefield accelerator

A tomographic diagnosis method was developed to systematically resolve the injection and acceleration processes of a monoenergetic electron beam in a laser-wakefield accelerator. It was found that all the monoenergetic electrons are injected at the same location in the plasma column and accelerated from 5 to 55 MeV energy in 200 microm distance. This is a direct measurement of the real acceleration gradient in a laser-wakefield accelerator, and the experimental data are consistent with the model of transverse wave breaking and beam loading for monoenergetic electron injection.