Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hyperfine spectroscopy in a quantum-limited spectrometer   We report measurements of electron spin echo envelope modulation (ESEEM)
performed at millikelvin temperatures in a custom-built high-sensitivity
spectrometer based on superconducting micro-resonators. The high quality factor
and small mode volume (down to 0.2pL) of the resonator allow to probe a small
number of spins, down to $5\cdot 10^2$. We measure 2-pulse ESEEM on two
systems: erbium ions coupled to $^{183}$W nuclei in a natural-abundance
$\text{CaWO}_4$ crystal, and bismuth donors coupled to residual $^{29}$Si
nuclei in a silicon substrate that was isotopically enriched in the $^{28}$Si
isotope. We also measure 3- and 5-pulse ESEEM for the bismuth donors in
silicon. Quantitative agreement is obtained for both the hyperfine coupling
strength of proximal nuclei, and the nuclear spin concentration.

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The categories of this paper are: adap-org
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The categories of this paper are: eess
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
4
The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: q-alg
14
The categories of this paper are: math-ph