J/A+A/657/A96 Detection of the propargyl radical at lambda 3mm (Agundez+, 2022)
Detection of the propargyl radical at lambda 3 mm.
Agundez M., Marcelino N., Cabezas C., Fuentetaja R., Tercero B.,
de Vicente P., Cernicharo J.
<Astron. Astrophys. 657, A96 (2022)>
=2022A&A...657A..96A 2022A&A...657A..96A (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: astrochemistry - line: identification - molecular processes -
ISM: molecules - radio lines: ISM
Abstract:
We report the detection of the propargyl radical (CH2CCH) in the
cold dark cloud TMC-1 in the lambda 3mm wavelength band. We recently
discovered this species in space toward the same source at a
wavelength of lambda 8mm. In those observations, various hyperfine
components of the 202-101 rotational transition, at 37.5GHz, were
detected using the Yebes 40m telescope. Here, we used the IRAM 30m
telescope to detect ten hyperfine components of the 505-404 rotational
transition, lying at 93.6GHz. The observed frequencies differ by
0.2MHz with respect to the predictions from available laboratory data.
This difference is significant for a radioastronomical search for
CH2CCH in interstellar sources with narrow lines. We thus included
the measured frequencies in a new spectroscopic analysis to provide
accurate frequency predictions for the interstellar search for
propargyl at mm wavelengths. Moreover, we recommend that future
searches for CH2CCH in cold interstellar clouds are carried out at
lambda 3mm, rather than at lambda 8 mm. The 505-404 transition is
about five times more intense than the 202-101 transition in TMC-1,
which implies that detecting the former requires about seven times
less telescope time than detecting the latter. We constrain the
rotational temperature of CH2CCH in TMC-1 to 9.9±1.5K, which
indicates that the rotational levels of this species are thermalized
at the gas kinetic temperature. The revised value of the column
density of CH2CCH (including ortho and para species) is
(1.0±0.2)x1014cm-2, and thus the CH2CCH/CH3CCH abundance
ratio is revised from slightly below one to nearly one. This study
opens the door for future detections of CH2CCH in other cold
interstellar clouds, making possible to further investigate the role
of this very abundant hydrocarbon radical in the synthesis of large
organic molecules such as aromatic rings.
Description:
tableA1.dat contains the predicted transition frequencies for CH2CCH
at 300K.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 77 4293 Predicted frequencies for CH2CCH at 300K
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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3- 13 F11.4 MHz Freq Calculated transition frequency
16- 21 F6.4 MHz O-C Uncertainty of calculated transition frequency
23- 29 F7.4 [nm2.MHz] logInt Base 10 logarithm of the integrated intensity
31 I1 --- DOF Degrees of freedom in the partition function
33- 41 F9.4 cm-1 Elow Energy of the lower state
42- 44 I3 --- gup Upper state degeneracy
47- 51 I5 --- Tag Species tag or molecular identifier
52- 65 A14 --- QNFMT Identifies the format of the quantum numbers
given in the field QN
68- 77 A10 --- QN Quantum numbers coded according to QNFMT
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Acknowledgements:
Marcelino Agundez, marcelino.agundez(at)csic.es
(End) Patricia Vannier [CDS] 10-Dec-2021