Low-energy electron impact coherence parameters for the 1 S 0 - 1 P 1 excitation in barium

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: B-fieldmentioning

confidence: 99%

“…Equation (3) then reduces to that for a conventional superelastic experiment (e.g. as adopted in [12][13][14]18]).…”

Section: The Alignment Parameters P Lin γmentioning

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

“…Since the majority of atomic targets have their first excited state above this range, the superelastic technique cannot be used and conventional electron-photon coincidence methods must be adopted. For this reason, the superelastic method has been constrained mostly to the alkali targets (see [8-15, 17, 18, 23-29, 33]), and more recently to the alkali-earth targets (see [16,[19][20][21][22][30][31][32]).…”

Section: Introductionmentioning

confidence: 99%

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

Murray¹,

Cvejanović

2003

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.

“…The experimental apparatus is a crossed-beam system where atomic targets are prepared in excited states by resonant laser pumping. The overall design has been introduced in previous work [2,[13][14][15][16][17], and is described in detail in [11].…”

Section: Experimental Apparatusmentioning

confidence: 99%

Differential cross sections for electron-impact excitation of laser-excited¹⁷⁴Yb (…6s6p ³P₁)

Hein¹,

Kidwai²,

Zetner³

et al. 2010

Self Cite

We have measured and calculated electron-impact excitation cross sections from the laser-excited Yb (. . . 6s6p 3 P 1 ) level to the higher-lying Yb (. . . 6s6p 1 P 1 ), (. . . 6s5d 3 D 1,2,3 ) and (. . . 6s7s 3 S 1 ) levels at 20 eV impact energy. Measurements were performed using a crossed-beam apparatus, with resonant laser radiation incident on the electron-atom interaction region, providing excited-state atomic targets. Calculations were performed in the relativistic convergent close-coupling (RCCC), convergent close-coupling (CCC), and relativistic distorted-wave (RDW) approximations. We present measured and calculated partial differential cross sections (PDCS), which relate to differential cross sections and electron-impact coherence parameters through the target state anisotropy introduced by the laser geometry. Using theoretical predictions of the h electron-impact coherence parameter, we present the differential cross section for the 3 P 1 -3 S 1 excitation.