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Université de Fribourg

Near-threshold absolute angle-differential cross sections for electron-impact excitation of argon and xenon

Allan, Michael ; Zatsarinny, O. ; Bartschat, K.

In: Physical Review A, 2006, vol. 74, p. 030701

Absolute angle-differential cross sections for electron-impact excitation of argon and xenon atoms to the lowest four np⁵(n+1)s levels, and the 5p⁵5d[7/2]₃ level in xenon, have been measured and calculated as a function of electron energy up to a few eV above threshold at a fixed scattering angle of 135°. For argon, very good agreement is observed...

Université de Fribourg

Study of resonances in formic acid by means of vibrational excitation by slow electrons

Allan, Michael

In: Journal of Phyics B: Atomic, Molecular and Optical Physics, 2006, vol. 39, no. 14, p. 2939-2947

Absolute differential elastic and vibrational excitation cross sections have been measured for formic acid at 135° from threshold to 5 eV. Most vibrationally inelastic cross sections have a narrow peak at threshold, followed by a broadband with a boomerang structure due to the known π* shape resonance. The cross section for the excitation of the O–H stretch vibration behaves differently, it...

Université de Fribourg

Low-energy electron attachment to SF₆ molecules: Vibrational structure in the cross-section for SF₆⁻ formation up to 1 eV

Braun, M. ; Ruf, M.-W. ; Hotop, Hartmut ; Allan, Michael

In: Chemical Physics Letters, 2006, vol. 419, p. 517–522

In high resolution electron attachment to SF₆, cusp structure due to interchannel coupling has been observed in the cross-section for SF₅⁻ formation at the thresholds for vibrational excitation of the SF₆(v₁) mode up to v₁ = 10. It is superimposed on the broad band peaking around 0.55 eV which has been previously attributed to attachment into a repulsive potential...

Université de Fribourg

Absolute angle-differential cross sections for electron-impact excitation of neon atoms from threshold to 19.5 eV

Allan, Michael ; Franz, K. ; Hotop, Hartmut ; Zatsarinny, O. ; Bartschat, K.

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2006, vol. 39, p. L139-L144

Absolute angle-differential cross sections for electron-impact excitation of neon atoms to the four levels with the (2p⁵3s) configuration have been determined both experimentally and theoretically for incident energies from threshold up to 19.5 eV at scattering angles of 135° and 180°. Excellent agreement between the experimental data and theoretical predictions, obtained by a Breit–Pauli...

Université de Fribourg

Elastic scattering, vibrational excitation, and attachment in low-energy electron-SF₆ scattering: Experiment and effective range theory

Fabrikant, Ilya I. ; Hotop, Hartmut ; Allan, Michael

In: Physical Review A, 2005, vol. 71, p. 022712-22721

Cross sections at low energies for vibrationally elastic and inelastic scattering, as well as electron attachment to SF₆, have been calculated using a multichannel effective range theory (ERT) with complex boundary conditions. The most active vibrational modes, the totally symmetric mode ν1 and the infrared active mode ν3, have been included in the calculation. The ERT parameters were fitted...

Université de Fribourg

Decay channels in the dissociative electron attachment to NO

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2004, vol. 37, p. L359-L363

Kinetic energy spectra of O⁻ from dissociative electron attachment (DEA) to NO were measured at 7.6, 8.0, 9.0 and 10.0 eV electron energy using a spectrometer with hemispherical energy selectors for both the incident electrons and the resulting ions. The measurements were performed at 10°, 30°, 90° and 135°. The capacity of the spectrometer to detect both slow and fast ions was verified and...

Université de Fribourg

The assignment of dissociative electron attachment bands in compounds containing hydroxyl and amino groups

Skalický, Tomás ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2004, vol. 37, p. 4849-4859

Dissociative electron attachment (DEA) spectra were recorded for methanol, phenol, diethylamine, tetramethylhydrazine, piperazine, pyrrole and N,N-dimethylaniline. Comparison with He I photoelectron spectra permitted the assignment of virtually all DEA bands in the saturated compounds to core excited Feshbach resonances with double occupation of Rydberg-like orbitals and various Koopmans' states...

Université de Fribourg

Electron collisions with NO: Elastic scattering, vibrational excitation, and ²Πi1/2 ⇌ ²Π3/2 transitions

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, p. 603

Absolute differential elastic and vibrational excitation cross sections have been measured for NO at 135° with resolution of the ²Π1/2 and ²Π3/2 spin-orbit components of the ground electronic term. The electronic fine structure excitation is dominated by the ³Σ⁻ and the ¹Δ resonances of NO⁻, the nonresonant contribution is very small. The cross section is very large, it has about the...

Université de Fribourg

Transitions between the ²Π₁͵₂ and ²Π₁͵₃ spin-orbit components of NO induced by impact of slow electrons

Allan, Michael

In: Physical Review Letters, 2004, vol. 93, p. 063201-63204

The electron impact cross section for the transition between the ²Π₁͵₂ and ²Π₁͵₃ spin-orbit components of the ground electronic term of nitric oxide, separated by 15 meV, has been measured as a function of electron energy at a scattering angle of Θ= 135°. It is dominated by the ³Σ⁻ and the ¹Δ resonances. Its magnitude is very large, at peak about equal to that of the elastic...

Université de Fribourg

Excitation of the four fundamental vibrations of CH₄ by electron impact near threshold

Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2005, vol. 38, p. 1679

Absolute differential elastic and vibrational excitation cross sections have been measured for CH₄ at 90° and from 0.1 to 1.5 eV, with the resolution of all four vibrational modes. Threshold peaks were observed in the excitation of the ν1, ν3 and ν4 modes, but not in the ν2 mode. These results are in good agreement with the recent calculation of Nishimura and Gianturco (2002 J. Phys. B:...