Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-LTE line-formation for hydrogen revisited   We discuss aspects of non-LTE line formation for hydrogen in early-type
stars. We evaluate the effect of variations in the electron-impact excitation
cross sections in model atoms of differing complexity by comparison with
observation. While the Balmer lines are basically unaffected by the choice of
atomic data, the Paschen, Brackett and Pfund series members allow us to
discriminate between the different models. Non-LTE calculations based on the
widely-used approximation formulae of Mihalas, Heasley & Auer and of Johnson
fail to simultaneously reproduce the optical and IR spectra over the entire
parameter range. The use of data from ab-initio calculations up to principal
quantum number n<=7 largely solves the problem. We recommend a reference model
using the available data. This model is of general interest because of the
ubiquity of the hydrogen spectrum.

12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat