J/A+A/621/A114 Deuterated methyl mercaptan (CH3SD) (Zakharenko+, 2019)
Deuterated methyl mercaptan (CH3SD):
Laboratory rotational spectroscopy and search toward IRAS 16293-2422 B.
Zakharenko O., Lewen F., Ilyushin V.V., Drozdovskaya M.N., Jorgensen J.K.,
Schlemmer S., Mueller H.S.P.
<Astron. Astrophys. 621, A114 (2019)>
=2019A&A...621A.114Z 2019A&A...621A.114Z (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Models
Keywords: methods: laboratory: molecular - techniques: spectroscopic -
ISM: molecules - astrochemistry - ISM: abundances - radio lines: ISM
Abstract:
Methyl mercaptan (also known as methanethiol), CH3SH, has been found
in the warm and dense parts of high- as well as low- mass star-forming
regions. The aim of the present study is to obtain accurate
spectroscopic parameters of the S-deuterated methyl mercaptan CH3SD
to facilitate astronomical observations by radio telescope arrays at
(sub)millimeter wavelengths. The rotational spectrum associated with
the large-amplitude internal rotation of the methyl group of methyl
mercaptan using an isotopically enriched sample has been measured in
the 150-510GHz frequency range using the Koeln millimeter wave
spectrometer. The analysis of the spectra has been performed up to the
second excited torsional state. The results of the modeling of these
data with the RAM36 program are presented. CH3SD was searched for,
but not detected, in data from the Atacama Large
Millimeter/submillimeter Array (ALMA) Protostellar Interferometric
Line Survey (PILS) of the deeply embedded protostar IRAS 16293-2422.
The derived upper limit corresponds to a degree of deuteration of at
most ∼18%.
Description:
input and output files.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
input.txt 153 5044 .txt input file for the program RAM36
output_CH3SD 191 19114 output file for CH3SD
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Description of file:
input.txt
The first 4 lines contain information about the operating mode of the program.
The next 6 lines remind the user of the format of the Hamiltonian parameters.
Then the list of parameters used in the fit is given. The line &&&END,,,,,,,,,
signals the end of this list. The parameter values are given in cm-1.
Each line with a Hamiltonian parameter contains the parameter name, a set of
7 integers that define the associated quantum mechanical operator, a value for
the parameter (i.e., for the coefficient of this operator), the
diagonalization stage in which the particular parameter is used, and a
float/fix flag.
The actual term is encoded by the set of 7 integers, which are
the powers of operators from the Hamiltonian expression. Thus:
k - (the first integer) corresponds to the power of J**2,
n - (the second integer) corresponds to the power of Jz,
p,q - are powers of Jx, Jy,
r - is the power of pa,
s - (the sixth integer) defines the argument of cos(3sa),
t - (the seventh integer) defines the argument of sin(3ta).
The next 7 lines contain the information necessary for the fitting process and
the predictions calculation.
Then the list of measured transition frequencies is given.
First a measured frequency is given. Then the assignment quantum numbers are
given. They are followed by the include/exclude switch 'ifit' and by the
measurement uncertainty. After that space for a comment is reserved.
The assignment consists of m, J, Ka, Kc quantum numbers. First the upper level
is given then the lower level is given. The labelling procedure in the program
determines from the eigenvector composition the levels which belong to each
particular m-state and then assigns Ka,Kc labels within each m state according
to the usual asymmetric top energy ordering scheme.
output_CH3SD
The output file is organized as follows. First the initial values of
parameters as well as different statistics on the experimental data (number
of transitions, number of blended transitions, number of levels included in
the fit etc.) are given. Then, for each iteration, the information on the
parameter changes and current rms deviation for different groups of data are
given. Then the list of the parameter values for the next iteration is
presented in the format suitable for the input file (so it can be copied and
pasted easily to the input file).
When the fit has converged or the maximum allowed number of iterations has
passed
the output of obtained results is given. The list of transitions with
J<Jmax from the input file is given three times.
First it is given in order of frequency, second it is given in the order it
appears in the input file, and third it is given sorted by spectroscopic
branches. In these lists the assignments of the levels are augmented by the
symmetry species labels from the G12 group (for V6) or from the G6 group
(for V3). When the list of transitions is presented sorted by branch the
expectation value of the (23)* operation is given and also if the transition
is blended you will find in the end of the line the letter 'b' with the
residual calculated from the special treatment of blends.
Detailled explanations on RAM36 could be found at
http://www.ifpan.edu.pl/~kisiel/introt/ram36/readmeram36.pdf
Xu, L.-H., Lees, R. M., Crabbe, G. T., et al. 2012, The Journal of Chemical
Physics, 137, 104313.
Tsunekawa, S., Taniguchi, I., Tambo, A., et al. 1989a, Journal of Molecular
Spectroscopy, 134, 63.
C. P. Endres, S. Schlemmer, P. Schilke, J. Stutzki, and H. S. P. Mueller,
The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic
and Molecular Data Centre, VAMDC, J. Mol. Spectrosc. 327, 95-104 (2016).
H. S. P. Mueller, F. Schloeder, J. Stutzki, and G. Winnewisser,
The Cologne Database for Molecular Spectroscopy, CDMS: a Useful Tool for
Astronomers and Spectroscopists, J. Mol. Struct. 742, 215-227 (2005).
H. S. P. Mueller, S. Thorwirth, D. A. Roth, and G. Winnewisser,
The Cologne Database for Molecular Spectroscopy Astron. Astrophys. 370,
L49-L52 (2001).
Ilyushin, V. V., Endres, C. P., Lewen, F., Schlemmer, S., Drouin, B. J.
2013, Journal of Molecular Spectroscopy, 290, 31.
Ilyushin, V. V., Kisiel, Z., Pszczokowski, L., Maeder, H., Hougen, J. T.
2010, Journal of Molecular Spectroscopy, 259, 26.
Smirnov, I. A., Alekseev, E. A., Ilyushin, V. V., et al. 2014,
Journal of Molecular Spectroscopy, 295, 44.
For further data associated with the CH3SD fits
http://www.astro.uni-koeln.de/site/vorhersagen/daten/Methanethiol/
Acknowledgements:
Olena Zakharenko, zakharenko(at)ph1.uni-koeln.de
(End) Patricia Vannier [CDS] 13-Nov-2018