Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fe3+ paramagnetic ion in {\alpha}-Al2 O3 energy levels revisited.
  Application to a 31 GHz Maser proposal   The molecular structure of a 3d 5 configuration ion in a trigonal ligand
field is theoretically established on the basis of the 252\times252 complete
energy matrice. The optical absorption and the electron paramagnetic resonance
spectra of the Fe3+ ion in the sapphire crystal ({\alpha}-Al2 O3) have been
studied by diagonalizing the complete energy matrice. The calculated results
are in very good agreement with previous experimental observations. The
strength of the transition probabilities between pairs of the energy levels
have been calculated to determine the possibility to achieve a population
inversion in the ground state by applying optical pumping to the crystal.
Preliminary results based on the computed transition parameters and on the
maser rate equations model show that a 31 GHz maser signal can be effectively
generated depending on the cryogenic resonator design.

11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin