J/A+A/680/A25 Laboratory spectroscopy of isobutene (Fatima+, 2023)
Millimeter and submillimeter spectroscopy of isobutene and its detection in the
molecular cloud G+0.693.
Fatima M., Mueller H.S.P., Zingsheim O., Lewen F., Rivilla V.M.,
Jimenez-Serra I., Martin-Pintado J., Schlemmer S.
<Astron. Astrophys. 680, A25 (2023)>
=2023A&A...680A..25F 2023A&A...680A..25F (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; Spectroscopy ;
Millimetric/submm sources ; Atomic physics
Keywords: astrochemistry - techniques: spectroscopic - molecular data -
ISM: molecules - radio lines: ISM -
ISM: individual objects: G+0.693-0.027
Abstract:
Isobutene ((CH3)2C=CH2) is one of the four isomers of butene
(C4H8). After the detection of propene (CH3CH=CH2) toward
TMC-1, and also in the warmer environment of the solar-type
protostellar system IRAS 16293-2422, one of the next alkenes,
isobutene, is thus a promising candidate to be searched for in space.
We aim to extend the limited line lists of the main isotopologue of
isobutene from the microwave to the millimeter region to obtain a
highly precise set of rest frequencies and to facilitate its detection
in the interstellar medium.
Description:
We investigated the rotational spectrum of the isobutene in the
35-370GHz range using absorption spectroscopy at room temperature.
Quantum-chemical calculations were carried out to evaluate vibrational
frequencies.
We determined new or improved spectroscopic parameters for isobutene
up to sixth order distortion constant. These new results enabled its
detection in the G+0.693 molecular cloud for the first time, where
recently propene has also been found. The column density
propene:isobutene ratio was determined to be about 3:1. The observed
spectroscopic parameters for isobutene are accurate enough that
calculated transition frequencies should be reliable up to 700GHz.
This will further help in observing it in other, warmer regions of the
ISM.
Objects:
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RA (2000) DE Designation(s)
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17 47 21.86 -28 21 27.1 G0.693-0.027 = GCM +0.693-0.027
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
c3h4.dat 62 3751 Transitions included in the fit of isobutene
((CH3)2C=CH2)
056526.dat 71 67617 *Catalogue file up to 1THz (J=99, T=300K)
generated from ERHAM program,
with additional blanks
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Note on 056526.dat: This format of the catalogue file is slightly different
from CDMS format.
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Byte-by-byte Description of file: c3h4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- J' Upper state J quantum number
4- 5 I2 --- Ka' Upper state Ka quantum number
7- 8 I2 --- Kc' Upper state Kc quantum number
10- 11 I2 --- J" Lower state J quantum number
13- 14 I2 --- Ka" Lower state Ka quantum number
16- 17 I2 --- Kc" Lower state Kc quantum number
19- 29 F11.4 MHz FreqObs Observed transition frequency
31- 37 F7.4 MHz (O-C) Observed minus calculated frequency
39- 43 F5.3 MHz Uncer Uncertainity used
45- 46 I2 --- qq' (IS1,IS2) internal rotor components (1)
48- 52 F5.2 --- wb ? Weight of the component in group of lines
54- 60 F7.4 MHz I(O-C) ? Individual O-C residual for line consisting
of several transitions
62 I1 --- Notes Source of data (2)
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Note (1): internal rotor components where
00 = A1A1, 01 = EE, 11 = A1E, 12 = EA1.
Note (2): References as follows:
1 = Gutowsky, H.S. & Germann, T. C. 1991, J. Mol. Spectrosc., 147, 91
2 = Demaison, J. & Rudolph, H. D. 1975, J. Mol. Struct., 24, 325
3 = Laurie, V. W. 1961, J. Chem. Phys., 34, 1516
4 = this study
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Byte-by-byte Description of file: 056526.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 11 F11.4 MHz Freq Predicted frequency
13- 18 F6.4 MHz Est(O-C) Estimated error
20- 26 F7.4 [nm2.MHz] logInt Base10 logarithm of the integrated intensity
28 I1 --- DR Degrees of freedom in the rotational
partition function
30- 39 F10.4 cm-1 Elo Lower state energy
41- 43 I3 --- Gup Upper state degeneracy
45- 49 I5 --- TAG CDMS entry tag
51- 52 I2 --- J' Upper state J quantum number
54- 55 I2 --- Ka' Upper state Ka quantum number
57- 58 I2 --- Kc' Upper state Kc quantum number
60 I1 --- q (IS1) internal rotor components (1)
62- 63 I2 --- J" Lower state J quantum number
65- 66 I2 --- Ka" Lower state Ka quantum number
68- 69 I2 --- Kc" Lower state Kc quantum number
71 I1 --- q' (IS2) internal rotor components (1)
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Note (1): (IS1,IS2) are internal rotor components where
00 = A1A1, 01 = EE, 11 = A1E, 12 = EA1.
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Acknowledgements:
Mariyam Fatima, fatima(at)ph1.uni-koeln.de
References:
Groner, P. 1997, J. Chem. Phys., 107, 4483
Groner, P. 2012, J. Mol. Spectrosc., 278, 52
(End) Patricia Vannier [CDS] 25-Sep-2023