Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gas phase detection and rotational spectroscopy of ethynethiol, HCCSH   We report the gas-phase detection and spectroscopic characterization of
ethynethiol ($\mathrm{HCCSH}$), a metastable isomer of thioketene
($\mathrm{H_2C_2S}$) using a combination of Fourier-transform microwave and
submillimeter-wave spectroscopies. Several $a$-type transitions of the normal
species were initially detected below 40 GHz using a supersonic
expansion-electrical discharge source, and subsequent measurement of
higher-frequency, $b$-type lines using double resonance provided accurate
predictions in the submillimeter region. With these, searches using a
millimeter-wave absorption spectrometer equipped with a radio frequency
discharge source were conducted in the range 280 - 660 GHz, ultimately yielding
nearly 100 transitions up to $^rR_0(36)$ and $^rQ_0(68)$. From the combined
data set, all three rotational constants and centrifugal distortion terms up to
the sextic order were determined to high accuracy, providing a reliable set of
frequency predictions to the lower end of the THz band. Isotopic substitution
has enabled both a determination of the molecular structure of $\mathrm{HCCSH}$
and, by inference, its formation pathway in our nozzle discharge source via the
bimolecular radical-radical recombination reaction $\mathrm{SH + C_2H}$, which
is calculated to be highly exothermic (-477 kJ/mol) using the HEAT345(Q)
thermochemical scheme.

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The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: q-alg