Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electron Spin-Relaxation Times of Phosphorus Donors in Silicon   Pulsed electron paramagnetic resonance measurements of donor electron spins
in natural phosphorus-doped silicon (Si:P) and isotopically-purified 28Si:P
show a strongly temperature-dependent longitudinal relaxation time, T1, due to
an Orbach process with DeltaE = 126 K. The 2-pulse echo decay is exponential in
28Si:P, with the transverse relaxation (decoherence) time, T2, controlled by
the Orbach process above ~12 K and by instantaneous diffusion at lower
temperatures. Spin echo experiments with varying pulse turning angles show that
the intrinsic T2 of an isolated spin in 28Si:P is ~60 ms at 7 K.

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The categories of this paper are: hep-th
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: math-ph