Benchmark Calculations for Electron Collisions with Ytterbium.

Cross sections for electron collisions with ytterbium are needed to model the enrichment process for the creation of Lu-177, which carries great promise in cancer treatments [1].  While a few experimental data and theoretical predictions are available [2,3], the comprehensive dataset needed for the modeling requires results for a large number of discrete transitions as well as ionization over an extended energy range.   We used the Dirac B-Spline R-matrix (DBSR) method [4] to perform such calculations with a variety of states included in the close-coupling expansion.   Our 20-state model (DBSR-20) couples the (4f¹⁴5p⁶6s²)¹S₀ ground state to all states with dominant configurations 4f¹⁴5p⁶6s6p and 4f¹⁴5p⁶5d6s, selected states with 4f¹⁴5p⁶5d 6p, and the (4f¹³5p⁶5d6s²)¹P₁ state, which provides an optically allowed 4f –> 5d single-electron excitation pathway from the ground state.  We compare the predictions with those from a 59-state (physical states only) approach as well as a DBSR-RMPS model, which accounts for coupling to the ionization continuum through pseudo-states that also provide the ionization cross section.

[1] https://www.oakridger.com/news/20190312/ornls-enriching-isotopes-again.

[2] B. Predojevic et al., J. Phys.  B 38 (2005), 1329 and 3489.

[3] C.J. Bostock et al., Phys. Rev. A 83 (2011) 052710.

[4] O. Zatsarinny and K. Bartschat, Phys. Rev. A 77 (2008) 062701.