J/A+A/640/A98 Propargylimine in laboratory and in space (Bizzocchi+, 2020)
Propargylimine in the laboratory and in space:
millimetre-wave spectroscopy and first detection in the ISM.
Bizzocchi L., Prudenzano D., Rivilla V.M., Pietropolli-Charmet A.,
Giuliano B.M., Caselli P., Martin-Pintado J., Jimenez-Serra I., Martin S.,
Requena-Torres M.A., Rico-Villas F., Zeng S., Guillemin J.-C.
<Astron. Astrophys. 640, A98 (2020)>
=2020A&A...640A..98B 2020A&A...640A..98B (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: molecular data - methods: laboratory: molecular -
methods: observational - techniques: spectroscopic - ISM: clouds -
ISM: molecules
Abstract:
Small imines containing up to three carbon atoms are present in the
interstellar medium. As alkynyl compounds are abundant in this medium,
propargylimine (2-propyn-1-imine, HC=C-CH=NH) thus represents a
promising candidate for a new interstellar detection.
The goal of the present work is to perform a comprehensive laboratory
investigation of the rotational spectrum of propargylimine in its
ground vibrational state in order to obtain a highly precise set of
rest-frequencies and to search it in space.
The rotational spectra of E and Z geometrical isomers of
propargylimine have been recorded in laboratory in the 83-500GHz
frequency interval. The measurements have been performed using a
source-modulation millimetre-wave spectrometer equipped with a
pyrolysis system for the production of unstable species.
High-level ab initio calculations were performed to assist the
analysis and to obtain reliable estimates for an extended set of
spectroscopic quantities.
We have searched for propargylimine at 3 and 2mm in the spectral
survey of the quiescent giant molecular cloud G+0.693-0.027 located in
the "Central Molecular Zone", close to the Galactic Centre.
About 1000 rotational transitions have been recorded for the E- and
Z-propargylimine, in the laboratory.
These new data have enabled the determination of a very accurate set
of spectroscopic parameters including rotational, quartic and sextic
centrifugal distortion constants.
The improved spectral data allow us to perform a successful search for
this new imine in the G+0.693-0.027 molecular cloud.
Eighteen lines of Z-propargylimine have been detected at level
>2.5*sigma, resulting in a column density estimate of
N=(0.24±0.02)x10-14cm-2. An upper limit was retrieved for the
higher-energy E isomer, which was not detected in the data.
The fractional abundance (w.r.t. H2) derived for Z-propargylimine is
1.8x10-10. We discuss the possible formation routes by comparing the
derived abundance with those measured in the source for possible
chemical precursors.
Description:
The rotational spectrum of propargylimine (PGIM) has been recorded
using the CASAC (Center for Astrochemical Studies Absorption Cell)
spectrometer at the Max-Planck-Institut fuer extraterrestrische Physik
in Garching.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablee1.dat 92 171 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of Z-PGIM with hyperfine structure
tablee2.dat 90 507 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of Z-PGIM without hyperfine structure
tablee3.dat 92 384 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of E-PGIM with hyperfine structure
tablee4.dat 90 359 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of E-PGIM without hyperfine structure
pgimehfs.cat 80 5618 SPCAT catalogue fon E-PGIM with HFS,
CDMS-like format
pgimerot.cat 80 5016 SPCAT catalogue fon E-PGIM without HFS,
CDMS-like format
pgimzhfs.cat 80 5563 SPCAT catalogue fon Z-PGIM with HFS,
CDMS-like format
pgimzrot.cat 80 6569 SPCAT catalogue fon Z-PGIM without HFS,
CDMS-like format
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Byte-by-byte Description of file (#): tablee1.dat tablee3.dat
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Bytes Format Units Label Explanations
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3- 4 I2 --- J' Upper state J
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' Upper state Kc
16- 17 I2 -- F' Upper state F
31- 32 I2 --- J Lower state J
35- 36 I2 --- Ka Lower state Ka
39- 40 I2 --- Kc Lower state Kc
44- 45 I2 -- F Lower state F
54- 65 F12.5 MHz Obs ?=- Measured line position (1)
71- 78 F8.5 MHz O-C ?=- Least-squares residual (1)
87- 92 F6.4 --- WeightBlend ? Relative weight in a line blend
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Note (1): Asterisks mark unresolved HFS blends.
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Byte-by-byte Description of file (#): tablee2.dat tablee4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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3- 4 I2 --- J' Upper state J
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' Upper state Kc
19- 20 I2 --- J Lower state J
22- 23 I2 --- Ka Lower state Ka
25- 26 I2 --- Kc Lower state Kc
40- 51 F12.5 MHz Obs ?=* Measured line position (1)
57- 64 F8.5 MHz O-C ?=* Least-squares residual (1)
74- 79 F6.4 --- WeightBlend ? Relative weight in a line blend
87- 90 A4 --- Ref Reference (2)
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Note (1): Asterisks mark unresolved asymetry doublets.
Note (2): References as follows:
(1) = Sugie et al. (1985, J. Mol. Spectrosc., 111, 83)
(2) = McNaughton et al. (1988, J. Mol. Struct., 190, 195)
(TW) = this work
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Acknowledgements:
Luca Bizzocchi, oedicnemus(at)gmail.com
(End) Patricia Vannier [CDS] 24-Jun-2020