Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exponential increase of energy level density in atoms: Th and Th II   We present analytical estimates and numerical calculations showing that the
energy level density in open-shell atoms increases exponentially with increase
of excitation energy. As an example, we use the relativistic Hartree-Fock and
configuration interaction methods to calculate the density of states of Th and
Th II. The result is used to estimate the effect of electrons on the nuclear
transition which is considered for the use in a nuclear clock.

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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: chem-ph