Abbreviated Journal Title
Phys. Rev. A
FINAL-STATE SYMMETRY; EXCITED-STATES; 2-ELECTRON ATOMS; HE; RESONANCE; SERIES; SATELLITES; AUTOIONIZATION; SPECTROMETRY; HE+(N=2); Optics; Physics, Atomic, Molecular & Chemical
Partial photoionization cross sections sigma(n) and photoelectron angular distributions beta(n) were measured for all possible final ionic states He+(n) in the region of the double excitations N(K,T)(A) up to the N=5 threshold. At a photon energy bandpass of 12 meV below the thresholds N=3,4, and 5, this level of differentiation offers the most critical assessment of the dynamics of the two-electron excitations to date. The experimental data are very well described by the most advanced theoretical calculations. Weaker double-excitation series with K=N-4 are clearly visible in the beta(n) data, and even previously unobserved extremely weak series members with A=-1 can be discerned, showing the high sensitivity of the angular resolved measurements. The shapes of the resonance-induced variations of sigma(n) or beta(n) in the double excitations below a given threshold N change radically depending on the final ionic state n but display striking similarities when comparing the satellite states with n=N-1 and n=N-2 below each threshold N. These systematic patterns may indicate a general rule for the underlying two-electron dynamics.
Physical Review A
Menzel, A.; Frigo, S. P.; Whitfield, S. B.; Caldwell, C. D.; and Krause, M. O., "Partial Photoionization Cross Sections And Photoelectron Angular Distributions For Double Excitations Up To The N=5 Threshold In Helium" (1996). Faculty Bibliography 1990s. 3051.