Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of 7p$_{1/2}$-state hyperfine structure and
  7s$_{1/2}$-7p$_{1/2}$ transition isotope shift in $^{203}$Tl and $^{205}$Tl   A two-step, two-color laser spectroscopy technique has been used to measure
the hyperfine splitting of the 7p$_{1/2}$ excited state in $^{203}$Tl and
$^{205}$Tl, as well as the isotope shift within the 7s$_{1/2}$ - 7p$_{1/2}$
transition. Our measured values for the hyperfine splittings, 2153.2(7) MHz (in
$^{203}$Tl) and 2173.3(8) MHz (in $^{205}$Tl), each differ by 20 MHz from
previously published values which quoted comparable precision. The transition
isotope shift of $^{203}$Tl relative to $^{205}$Tl was measured to be 534.4(9)
MHz. In our experiment, one laser was locked to the thallium ground-state
6p$_{1/2}$ - 7s$_{1/2}$ 378 nm transition, while the second, spatially
overlapping laser was scanned across the 7s$_{1/2}$(F=1) - 7p$_{1/2}$(F=0,1)
hyperfine transitions. To facilitate accurate frequency calibration,
radio-frequency modulation of the laser was used to create sidebands in the
absorption spectrum.

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The categories of this paper are: hep-lat
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The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: astro-ph
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The categories of this paper are: econ
0
The categories of this paper are: hep-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: math