Design of a non-magnetic translator for use in vacuum systems

Super-elastic scattering processes can be considered as the 'time reversal' of electron-photon coincidence measurements, with the advantage that data are accumulated thousands of times faster. This allows a far more extensive and accurate study of electron excitation of atoms which can also be excited using laser radiation. The application of a newly invented magnetic angle changing (MAC) device to these experiments has allowed the complete scattering geometry to be accessed for the first time, and experimental methods adopted in these new experiments are discussed here. Data are presented for excitation of the 4 1 P 1 state of calcium by electron impact at scattering angles from near 0 • to beyond 180 • , with incident energies of 45 eV and 55 eV. The results are compared to the DWBA theory of Stauffer and colleagues, with generally excellent agreement.

Section: Methodsmentioning

confidence: 99%

Low energy super-elastic scattering studies of calcium over the complete angular range using a magnetic angle changing device

Hussey

Murray

MacGillivray

et al. 2008

“…The trace laser operating at λ = 650 nm was mounted on a plate below the interaction region as shown in figure 4. While the spectrometer was outside the vacuum chamber, the diode laser was accurately positioned using two custom designed vacuum compatible translators so that its beam passed through the interaction region defined by the analysers, electron gun and oven [53]. A 650 nm interference filter was placed in the path of the laser beam directly above the laser diode to protect the laser from damage when the 423 nm laser beam was operating.…”

Section: Experimental Techniquementioning

confidence: 99%

Low energy superelastic scattering from the 4¹P₁state of calcium in an (e, 2e) spectrometer

Murray¹,

Cvejanović

2003

Self Cite

Atomic collision parameters have been derived for electron impact excitation of calcium using the superelastic scattering method,at incident energies equivalent to 20, 25 and 35 eV. The pseudo-Stokes parameters for the superelastic process were determined, and the parameters P + lin , L + ⊥ , γ + and P + tot derived for the 4 1 P 1 state. The results are compared to a relativistic distorted-wave approximation (RDWA) theory, and to previous experimental results. At the highest incident energy the results presented here compare well with theory, but at the lowest energy, significant disagreement between theory and experiment is observed.

“…In particular, the electron gun has been rebuilt so that the maximum backward scattering angles are increased from θ a,b = 125 • to θ a,b = 140 • . A further modification has been the inclusion of a vacuum compatible XY-translator to adjust the position of the electron gun accurately [17], together with a permanently mounted laser diode which traces the direction of the incident electron beam through the interaction region. These additions simplify the alignment of the spectrometer over the angular geometry which can be accessed.…”

Section: Methodsmentioning

confidence: 99%

(e, 2e) ionization measurements from the 3σ_gand 2σ_u* states of N₂—comparison between experiment and theoretical predictions of the effects of exchange, polarization and interference

Murray

Hussey

Gao

et al. 2006

Self Cite

Gao et al (2005 Phys. Rev. A 72 032721) have predicted a Young's type interference effect in the fully differential cross sections for ionization of the 3σ g state of N 2 for highly asymmetric collisions with one electron detector fixed at very small scattering angles (1 • or 10 •). The purpose of this work was to look for this interference effect at a larger scattering angle. (e, 2e) ionization measurements have been conducted from the 3σ g and 2σ * u states of N 2 in a coplanar asymmetric geometry, where one electron emerges in the forward direction and the correlated electron is measured as a function of scattering angle. Both final-state electrons have an energy of 30 eV, and the forward scattering angle was θ a = 22 • relative to the incident beam direction. The theoretical prediction is that there should be a strong interference peak near 180 •. The measurements were carried out from the 3σ g state over a range of scattering angles from θ b ∼ 10 • to θ b ∼ 170 • using a magnetic angle changing spectrometer. The present experimental results for 3σ g find a normal binary peak plus another peak at back angles in the vicinity of 180 •. Consequently, this work supports the possibility of a strong Young's type interference effect for small fixed scattering angles.