Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Breakdown of Angular Momentum Selection Rules in High Pressure Optical
  Pumping Experiments   We present measurements, using two complementary methods, of the breakdown of
atomic angular momentum selection rules in He-broadened Rb vapor. Atomic dark
states are rendered weakly absorbing due to fine-structure mixing during Rb-He
collisions. The effect substantially increases the photon demand for optical
pumping of dense vapors.

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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph