J/A+A/676/L5 Discovery in space and in laboratory of H2CCCN (Cabezas+, 2023)
Laboratory and astronomical discovery of the cyanovinyl radical H2CCCN.
Cabezas C., Tang J., Agundez M., Seiki K., Sumiyoshi Y., Ohshima Y.,
Tercero B., Marcelino N., Fuentetaja R., de Vicente P., Endo Y.,
Cernicharo J.
<Astron. Astrophys. 676, L5 (2023)>
=2023A&A...676L...5C 2023A&A...676L...5C (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: molecular data - methods: laboratory: molecular -
line: identification - ISM: molecules - astrochemistry -
ISM: individual objects: TMC-1
Abstract:
We report the first laboratory and interstellar detection of the
alpha-cyano vinyl radical (H2CCCN). This species was produced in the
laboratory by an electric discharge of a gas mixture of vinyl cyanide,
CH2CHCN, and Ne, and its rotational spectrum was characterized using
a Balle-Flygare narrowband-type Fourier-transform microwave
spectrometer operating in the frequency region of 8-40GHz. The
observed spectrum shows a complex structure due to tunneling
splittings between two torsional sublevels of the ground vibronic
state, 0+ and 0-, derived from a large-amplitude inversion motion. In
addition, the presence of two equivalent hydrogen nuclei makes
necessary to discern between ortho- and para-H2CCCN. A least squares
analysis reproduces the observed transition frequencies with a
standard deviation of ca. 3kHz. Using the laboratory predictions, this
radical is detected in the cold dark cloud TMC-1 using the Yebes 40m
telescope and the QUIJOTE line survey. The 404-303 and 505-404
rotational transitions, composed of several hyperfine components, were
observed in the 31.0-50.4GHz range. Adopting a rotational temperature
of 6K we derive a column density of (1.4±0.2)*10-11cm-2 and
(1.1±0.2)*10-11cm-2 for ortho-H2CCCN and para-H2CCCN,
respectively. The reactions C + CH3CN, and perhaps also N +
CH2CCH, emerge as the most likely routes to H2CCCN in TMC-1.
Description:
tablea3.dat and tablea4.dat contain the predicted rotational
transitions frequencies up to 300GHz for ortho-H2C3N and
para-H2C3N, respectively
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea3.dat 79 28770 Predicted frequencies for ortho-H2C3N
tablea4.dat 79 29844 Predicted frequencies for para-H2C3N
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Byte-by-byte Description of file: tablea3.dat tablea4.dat
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Bytes Format Units Label Explanations
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3- 13 F11.4 MHz Freq Frequency
16- 21 F6.4 MHz Unc Uncertainty
22- 29 F8.4 [nm+2.MHz] logInt Base 10 logarithm of the integrated intensity
31 I1 cm-1 DOF Degrees of freedom of rotation partition
function
33- 41 F9.4 cm-1 Elow Lower state energy
43- 44 I2 --- gup Upper state degeneracy
47- 59 A13 --- TAG Molecular identifier
60- 61 I2 --- N' Quantum number N for upper level
62- 63 I2 --- Ka' Quantum number Ka for upper level
64- 65 I2 --- Kc' Quantum number Kc for upper level
66- 67 I2 --- TSP' TSP aggregate spin number for upper level
68- 69 I2 --- F' Quantum number F for upper level
70- 71 I2 --- N" Quantum number N for lower level
72- 73 I2 --- Ka" Quantum number Ka for lower level
74- 75 I2 --- Kc" Quantum number Kc for lower level
76- 77 I2 --- TSP" TSP aggregate spin number for lower level
78- 79 I2 --- F" Quantum number F for lower level
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Acknowledgements:
Carlos Cabezas, carlos.cabezas(at)csic.es
(End) Patricia Vannier [CDS] 20-Jul-2023