Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hyperfine structure in the microwave spectra of ultracold polar
  molecules   We investigate the microwave spectra of ultracold alkali metal dimers in
magnetic, electric and combined fields, taking account of the hyperfine
structure due to the nuclear spins. We consider the molecules 41K87Rb and
7Li133Cs, which are the targets of current experiments and demonstrate two
extremes of large and small nuclear quadrupole coupling. We calculate the
frequencies and intensities of transitions that may be used to transfer
ultracold molecules between hyperfine states in a magnetic field, employing
different polarizations of microwave radiation. In an electric field, the
hyperfine levels display narrow avoided crossings at specific fields that we
explain in terms of molecular alignment. The hyperfine splittings that arise in
electric fields may hinder individual addressing in schemes to use ultracold
molecules in quantum computation, but the structure of the spectra is
suppressed in combined fields.

10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an