Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Saturated-absorption spectroscopy: Eliminating crossover resonances
  using co-propagating beams   We demonstrate a new technique for saturated-absorption spectroscopy using
co-propagating beams that does not have the problem of crossover resonances.
The pump beam is locked to a transition and its absorption signal is monitored
while the probe beam is scanned. As the probe comes into resonance with another
transition, the pump absorption is reduced and the signal shows a Doppler-free
dip. We use this technique to measure hyperfine intervals in the $D_2$ line of
$^{85}$Rb with a precision of 70 kHz, and to resolve hyperfine levels in the
$D_2$ line of $^{39}$K that are less than 10 MHz apart.

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The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex