J/A+A/621/A111 Rest frequencies of ketenyl (HCCO and DCCO) (Chantzos+, 2019)
Rotational spectroscopy of the HCCO and DCCO radicals in the millimeter and
submillimeter range.
Chantzos J., Spezzano S., Endres C., Bizzocchi L., Lattanzi V., Laas J.,
Vasyunin A., Caselli P.
<Astron. Astrophys. 621, A111 (2019)>
=2019A&A...621A.111C 2019A&A...621A.111C (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: molecular data - methods: laboratory: molecular -
techniques: spectroscopic - radio lines: ISM
Abstract:
The ketenyl radical, HCCO, has recently been detected in the ISM for
the first time. Further astronomical detections of HCCO will help us
understand its gas-grain chemistry, and subsequently revise the
oxygen-bearing chemistry towards dark clouds. Moreover, its deuterated
counterpart, DCCO, has never been observed in the ISM. HCCO and DCCO
still lack of a broad spectroscopic investigation although they
exhibit a significant astrophysical relevance.
In this work we aim to measure the pure rotational spectra of the
ground state of HCCO and DCCO in the millimeter and submillimeter
region, considerably extending the frequency range covered by previous
studies.
The spectral acquisition was performed using a frequency-modulation
absorption spectrometer between 170 and 650GHz. The radicals were
produced in a low-density plasma generated from a select mixture of
gaseous precursors. For each isotopologue we were able to detect and
assign more than 100 rotational lines.
The new lines have significantly enhanced the previous data set
allowing the determination of highly precise rotational and
centrifugal distortion parameters. In our analysis we have taken into
account the interaction between the ground electronic state and a
low-lying excited state (Renner-Teller pair) which enables the
prediction and assignment of rotational transitions with Ka up to 4.
The present set of spectroscopic parameters provides highly accurate,
millimeter and submillimeter rest-frequencies of HCCO and DCCO for
future astronomical observations. We also show that towards the
pre-stellar core L1544, ketenyl peaks in the region where c-C3H2
peaks, suggesting that HCCO follows a predominant hydrocarbon
chemistry, as already proposed by recent gas-grain chemical models.
Description:
In the present work, the rotational spectra were taken with the
frequency-modulation mm/sub-mm Absorption Cell spectrometer developed
at the Center for Astrochemical Studies (CASAC) in Garching.
iWe made a rotational analysis of the ketenyl radical HCCO and its
deuterated counterpart DCCO. For each isotopolog we measured and
assigned more than 100 lines. We extended the measurements up to
∼650 GHz, which helped us improve the determination of the
spectroscopic parameters with respect to the previous study by Endo &
Hirota (1987, J. Chem. Phys., 86, 4319). In particular, we measured
the rotational transitions with N ranging from 8 to 27 for HCCO and
with N=9-33 for DCCO with a maximum Ka of 4.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 97 360 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of HCCO
table2.dat 90 229 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of DCCO
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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3- 4 I2 --- N' Upper state N
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' Upper state Kc
15- 16 I2 --- v' Upper state v
19- 20 I2 --- J' Upper state J
23- 24 I2 --- F' Upper state F
29- 30 I2 --- N Lower state N
33- 34 I2 --- Ka Lower state Ka
37- 38 I2 --- Kc Lower state Kc
41- 42 I2 --- v Lower state v
46- 47 I2 --- J Lower state J
51- 52 I2 --- F Lower state F
57- 66 F10.3 MHz Obs Measured line position
71- 78 F8.5 MHz O-C Least-squares residual
83- 87 F5.3 MHz unc Assumed uncertainty
94- 97 A4 --- Ref Reference (G1)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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3- 4 I2 --- N' Upper state N
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' Upper state Kc
15- 16 I2 --- v' Upper state v
19- 20 I2 --- J' Upper state J
25- 26 I2 --- N lower state N
29- 30 I2 --- Ka Lower state Ka
33- 34 I2 --- Kc Lower state Kc
37- 38 I2 --- v Lower state v
41- 42 I2 --- J Lower state J
48- 57 F10.3 MHz Obs Measured line position
63- 70 F8.5 MHz O-C Least-squares residual
76- 80 F5.3 MHz unc Assumed uncertainty
87- 90 A4 --- Ref Reference (G1)
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Global notes:
Note (G1): References as follows:
Endo = Endo & Hirota, 1987, Journal of Chemical Physics, 86, 4319
Ohs = Ohshima & Endo, 1993, Journal of Molecular Spectroscopy, 159, 458
TW = this work
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Acknowledgements:
Johanna Chantzos, chantzos(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 28-Nov-2018