Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hyperfine level structure in nitrogen-vacancy centers near the
  ground-state level anticrossing   Energy levels of nitrogen-vacancy centers in diamond were investigated using
optically detected magnetic-resonance spectroscopy near the electronic
ground-state level anticrossing (GSLAC) at an axial magnetic field around
102.4~mT in diamond samples with a nitrogen concentration of 1~ppm and 200~ppm.
By applying radiowaves in the frequency ranges from 0 to 40 MHz and from 5.6 to
5.9 GHz, we observed transitions that involve energy levels mixed by the
hyperfine interaction. We developed a theoretical model that describes the
level mixing, transition energies, and transition strengths between the
ground-state sublevels, including the coupling to the nuclear spin of the NV
center\textquotesingle s $^{14}$N and $^{13}$C atoms. The calculations were
combined with the experimental results by fitting the ODMR spectral lines based
on a theoretical model, which yielded information about the polarization of
nuclear spins. This study is important for the optimization of experimental
conditions in GSLAC-based applications, e.g., microwave-free magnetometry and
microwave-free nuclear-magnetic-resonance probes.

23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph