Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hyperfine-interaction- and magnetic-field-induced
  Bose-Einstein-statistics suppressed two-photon transitions   Two-photon transitions between atomic states of total electronic angular
momentum $J_a=0$ and $J_b=1$ are forbidden when the photons are of the same
energy. This selection rule is analogous to the Landau-Yang theorem in particle
physics that forbids decays of vector particle into two photons. It arises
because it is impossible to construct a total angular momentum $J_{2\gamma}=1$
quantum-mechanical state of two photons that is permutation symmetric, as
required by Bose-Einstein statistics. In atoms with non-zero nuclear spin, the
selection rule can be violated due to hyperfine interactions. Two distinct
mechanisms responsible for the hyperfine-induced two-photon transitions are
identified, and the hyperfine structure of the induced transitions is
evaluated. The selection rule is also relaxed, even for zero-nuclear-spin
atoms, by application of an external magnetic field. Once again, there are two
similar mechanisms at play: Zeeman splitting of the intermediate-state
sublevels, and off-diagonal mixing of states with different total electronic
angular momentum in the final state. The present theoretical treatment is
relevant to the ongoing experimental search for a possible
Bose-Einstein-statistics violation using two-photon transitions in barium,
where the hyperfine-induced transitions have been recently observed, and the
magnetic-field-induced transitions are being considered both as a possible
systematic effect, and as a way to calibrate the measurement.

21
The categories of this paper are: adap-org
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph