Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solving close-coupling equations in momentum space without singularities
  for charged targets   The analytical treatment of the Greens function in the convergent
close-coupling method [Bray et al. Comp. Phys. Comm. 203 147 (2016)] has been
extended to charged targets. Furthermore, we show that this approach allows for
calculation of cross sections at zero channel energy. For neutral targets this
means the electron scattering length may be obtained from a single calculation
with zero incident energy. For charged targets the non-zero excitation cross
sections at thresholds can also be calculated by simply setting the incident
energy to the exact threshold value. These features are demonstrated by
considering electron scattering on H and He+.

12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph