Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An iterative technique for solving equations of statistical equilibrium   Superlevel partitioning is combined with a simple relaxation procedure to
construct an iterative technique for solving equations of statistical
equilibrium. In treating an $N$-level model atom, the technique avoids the
$N^{3}$ scaling in computer time for direct solutions with standard linear
equation routines and also does not fail at large $N$ due to the accumulation
of round-off errors. In consequence, the technique allows detailed model atoms
with $N \ga 10^{3}$, such as those required for iron peak elements, to be
incorporated into diagnostic codes for analysing astronomical spectra. Tests
are reported for a 394-level Fe II ion and a 1266-level Ni I--IV atom.

3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math