Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Precision lifetime measurements of a single trapped ion with ultrafast
  laser pulses   We report precision measurements of the excited state lifetime of the $5p$
$^2P_{1/2}$ and $5p$ $^2P_{3/2}$ levels of a single trapped Cd$^+$ ion. The ion
is excited with picosecond laser pulses from a mode-locked laser and the
distribution of arrival times of spontaneously emitted photons is recorded. The
resulting lifetimes are 3.148 $\pm$ 0.011 ns and 2.647 $\pm$ 0.010 ns for
$^2P_{1/2}$ and $^2P_{3/2}$ respectively. With a total uncertainty of under
0.4%, these are among the most precise measurements of any atomic state
lifetimes to date.

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The categories of this paper are: acc-phys
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The categories of this paper are: econ
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas