Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral signatures of excess-proton waiting and transfer-path dynamics
  in aqueous hydrochloric acid solutions   Signatures of solvated excess protons in infrared difference absorption
spectra, such as the continuum band between the water bend and stretch bands,
have been experimentally known for a long time, but the theoretical basis for
linking spectral signatures with the microscopic proton-transfer mechanism so
far relied on normal-mode analysis. We analyze the excess-proton dynamics in ab
initio molecular-dynamics simulations of aqueous hydrochloric acid solutions by
trajectory-decomposition techniques. The continuum band in the 2000 - 3000
cm$^{-1 }$ range is shown to be due to normal-mode oscillations of temporary
H$_3$O$^+$ complexes. An additional prominent peak at 400 cm$^{-1}$ reports on
the coupling of excess-proton motion to the relative vibrations of the two
flanking water molecules. The actual proton transfer between two water
molecules, which for large water separations involves crossing of a barrier and
thus is not a normal mode, is characterized by two characteristic time scales:
Firstly, the waiting time for transfer to occur in the range of 200 - 300 fs,
which leads to a broad weak shoulder around ~100 cm$^{-1}$, consistent with our
experimental THz spectra. Secondly, the mean duration of a transfer event of
about 14 fs, which produces a rather well-defined spectral contribution around
1200 cm$^{-1}$ and agrees in location and width with previous experimental
mid-infrared spectra.

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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: cs
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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: eess