Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Isotope Shifts in the 7s$\rightarrow$8s Transition of Francium:
  Measurements and Comparison to \textit{ab initio} Theory   We observe the electric-dipole forbidden $7s\rightarrow8s$ transition in the
francium isotopes $^{208-211}$Fr and $^{213}$Fr using a two-photon excitation
scheme. We collect the atoms online from an accelerator and confine them in a
magneto optical trap for the measurements. In combination with previous
measurements of the $7s\rightarrow7p_{1/2}$ transition we perform a King Plot
analysis. We compare the thus determined ratio of the field shift constants
(1.230 $\pm$ 0.019) to results obtained from new ab initio calculations (1.234
$\pm$ 0.010) and find excellent agreement.

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The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
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
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin