A joint experimental and theoretical study of near-threshold electron-impact excitation of the 33S and 31S states in helium is reported. A high-resolution electron spectrometer is used to study integral cross sections in the energy region of the n = 3 − 5 negative-ion resonances. Photons are detected from the decay of the two states and the observed intensities are normalized to theoretical predictions using a new B-spline R-matrix (close-coupling) method that allows for non-orthogonal orbitals to improve the target description. Remarkable agreement between experiment and theory is demonstrated in both the overall energy dependence of the cross section and the fine details of a wealth of resonance structures. A detailed list of the resonances in the individual partial waves, along with their widths, is presented.
|Journal||Journal of Physics B: Atomic, Molecular and Optical Physics|
|Publication status||Published - 2006|
Stepanovic, M., Minic, M., Cvejanovic, D., Jureta, J., Kurepa, J., Cvejanovic, S., Zatsarinny, O., & Bartschat, K. (2006). Integral cross sections for electron-impact excitation of the 3(3)S and 3(1)S states of He near threshold. Journal of Physics B: Atomic, Molecular and Optical Physics, 39(6), 1547-1561.