J/A+A/612/A56 Rest frequencies of dithioformic acid (Prudenzano+, 2018)
Accurate millimetre and submillimetre rest frequencies
for cis- and trans-dithioformic acid, HCSSH.
Prudenzano D., Laas J., Bizzocchi L., Lattanzi V., Endres C.,
Giuliano B.M., Spezzano S., Palumbo M.E., Caselli P.
<Astron. Astrophys. 612, A56 (2018)>
=2018A&A...612A..56P 2018A&A...612A..56P (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Radio lines
Keywords: molecular data - methods: laboratory: molecular -
techniques: spectroscopic - radio lines: ISM - ISM: molecules
Abstract:
A better understanding of sulphur chemistry is needed to solve the
interstellar sulphur depletion problem. A way to achieve this goal is
to study new S-bearing molecules in the laboratory, obtaining accurate
rest frequencies for an astronomical search. We focus on dithioformic
acid, HCSSH, which is the sulphur analogue of formic acid.
The aim of this study is to provide an accurate line list of the two
HCSSH trans and cis isomers in their electronic ground state and a
comprehensive centrifugal distortion analysis with an extension of
measurements in the millimetre and submillimetre range.
We studied the two isomers in the laboratory using an absorption
spectrometer employing the frequency-modulation technique. The
molecules were produced directly within a free-space cell by glow
discharge of a gas mixture. We measured lines belonging to the
electronic ground state up to 478GHz, with a total number of 204 and
139 new rotational transitions, respectively, for trans and cis
isomers. The final dataset also includes lines in the centimetre range
available from literature.
The extension of the measurements in the mm and submm range lead to an
accurate set of rotational and centrifugal distortion parameters. This
allows us to predict frequencies with estimated uncertainties as low
as 5kHz at 1mm wavelength. Hence, the new dataset provided by this
study can be used for astronomical search.
Description:
The measurements were performed using the CASAC (Center for
Astrochemical Studies Absorption Cell) spectrometer at the
Max-Planck-Institut fuer extraterrestrische Physik. Full details of
the experimental apparatus can be found in Bizzocchi et al.
(2017A&A...602A..34B 2017A&A...602A..34B). The instrument employs the frequency modulation
technique in the mm and submm range and is equipped with a glow
discharge cell for production of unstable species. Measurements were
carried out at room temperature to avoid condensation of the
precursors. Dithioformic acid was produced by a 40mA DC discharge
(∼0.8kV) from a 1:1 mixture of CS2 and H2, diluted in Ar buffer gas.
The total pressure in the cell was 20-30mTorr (27-40ubar).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 82 226 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of trans-HCSSH
table2.dat 82 156 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of cis-HCSSH
table3.dat 86 647 Predicted rest frequencies, estimated accuracies,
lines strenghts, energy of the upper states and
Einstein A coefficients for the ground
vibrational state of trans-HCSSH
table4.dat 86 715 Predicted rest frequencies, estimated accuracies,
lines strenghts, energy of the upper states and
Einstein A coefficients for the ground
vibrational state of cis-HCSSH
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See also:
J/A+A/602/A34 : HOCO+ and DOCO+ rest frequencies (Bizzocchi+, 2017)
Byte-by-byte Description of file(#): table1.dat table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 4 I2 --- J' Upper state J
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' ?=* Upper state Kc (1)
17- 18 I2 --- J Lower state J
21- 22 I2 --- Ka Lower state Ka
25- 26 I2 --- Kc ?=* Lower state Kc (1)
39- 50 F12.5 MHz Obs Measured line position
54- 61 F8.5 MHz O-C Least-squares residual
68- 72 F5.3 MHz unc Assumed uncertainty
80- 82 A3 --- Ref Reference (2)
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Note (1): * mark unresolved asymmetry doublets.
Note (2): Referneces as follows:
Bak = Bak et al., 1978, , J. Mol. Spectr., 69, 401
TW = this work
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Byte-by-byte Description of file(#): table3.dat table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
4- 5 I2 --- J' Upper state J
7 A1 --- --- [(]
8- 9 I2 --- Ka' Upper state Ka
10 A1 --- --- [,]
11- 12 I2 --- Kc' Upper state Kc
13 A1 --- --- [)]
21- 22 I2 --- J Lower state J
24 A1 --- --- [(]
25- 26 I2 --- Ka Lower state Ka
27 A1 --- --- [,]
28- 29 I2 --- Kc Lower state Kc
30 A1 --- --- [)]
39- 48 F10.3 MHz RestFreq Rest frequency
50 A1 --- --- [(]
51- 54 F4.1 kHz e_RestFreq Estimated error on rest frequency
55 A1 --- --- [)]
57- 65 E9.3 D+2 LineStr transition strength (Debye2)
68- 74 F7.3 cm-1 Eupper Upper state energy
78- 86 E9.3 s-1 A Einstein's A coefficient
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Acknowledgements:
Domenico Prudenzano, prudenzano(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 11-Jan-2018