J/MNRAS/520/4089 Millimeter-wave spectrum of 2-propanimine (Zou+, 2023)
Millimeter-wave spectrum of 2-propanimine.
Zou L., Guillemin J.-C., Belloche A., Jorgensen J.K., Margules L.,
Motiyenko R.A., Groner P.
<Mon. Not. R. Astron. Soc. 520, 4089-4102 (2023)>
=2023MNRAS.520.4089Z 2023MNRAS.520.4089Z (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Spectroscopy
Keywords: astrochemistry - molecular data - ISM: molecules -
methods: laboratory: molecular
Abstract:
Up to date, only six imines have been detected in the interstellar
medium. The 3-carbon imine, 2-propanimine ((CH3)2C=NH), is
predicted to be the structural isomer with the lowest energy in the
C3H7N group, and appears to be a good candidate for astronomical
searches. Unexpectedly, no microwave or millimeter wave spectrum is
available for 2-propanimine. In this work, we provide the first
high-resolution millimeter wave spectrum of 2-propanimine and its
analysis. With the guide of this laboratory measurement, we aim to
search for 2-propanimine in two molecule-rich sources Sgr B2(N) and
IRAS 16293-2422 using observations from the Atacama Large
Millimeter/submillimeter Array (ALMA). Starting from a synthesized
sample, we measured the spectrum of 2-propanimine from 50 to
500GHz, and the ground state lines are successfully assigned and
fitted using XIAM and ERHAM programs with the aid of theoretical
calculations. The barriers to internal rotation of the two CH3 tops
are determined to be 531.956(64)cm-1 and 465.013(26)cm-1 by XIAM.
These data are able to provide reliable prediction of transition
frequencies for astronomical search. Although a few line matches
exist, no confirmed detection of 2-propanimine has been found in the
hot molecular core Sgr B2(N1S) and the Class 0 protostar IRAS 16293B.
Upper-limits of its column density have been derived, and indicate
that 2-propanimine is at least 18 times less abundant than methanimine
in Sgr B2(N1S), and is at most 50-83 per cent of methanimine in IRAS
16293B.
Description:
The measure frequency line list and the prediction of 2-propanimine
[(CH3)_2C=NH] for the ground state.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 27259 2-propanimine measured frequency
table4.dat 75 90812 2-propanimine prediction up to 1 THz
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See also:
J/ApJ/853/139 : 1-(Z)-1-propanimine rotational transitions (Sil+, 2018)
J/A+A/663/A132 : 1-propanimine measured freq. and residuals (Margules+, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 -- J'' Quantum number J of the upper state
4- 6 I3 -- Ka'' Quantum number Ka of the upper state
7- 9 I3 -- Kc'' Quantum number Kc of the upper state
10- 12 I3 -- s1 Quantum number sigma_1
13- 15 I3 -- J' Quantum number J of the lower state
16- 18 I3 -- Ka' Quantum number Ka of the lower state
19- 21 I3 -- Kc' Quantum number Kc of the lower state
22- 24 I3 -- s2 Quantum number sigma_2
25- 36 F12.3 MHz Freq Line frequency observed
37- 43 F7.3 MHz e_Freq Line frequency uncertainty
44- 50 F7.3 MHz RelInt Relative intensity for blended lines (1)
51- 58 F8.4 MHz Diff Frequency difference (obs - calc)
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Note (1): For single lines, the relative intensity is always unity (1.00).
For blended lines, the sum of the relative intensities is unity (1.00).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 13 F13.4 MHz Freq Frequency of the line (1)
14- 21 F8.4 MHz e_Freq Estimated error
22- 29 F8.4 [nm+2.MHz] logInt Base 10 log of the integrated intensity (3)
30- 31 I2 -- DR Degrees of freedom
32- 41 F10.4 cm-1 Elo Lower state energy
42- 44 I3 -- Gup Upper state degeneracy (3)
45- 51 I7 -- TAG Species tag
52- 55 I4 -- QNFMT Quantum number (QN) format identifier (2)
56- 57 I2 -- J'' QN J of the upper state
58- 59 I2 -- Ka'' QN Ka of the upper state
60- 61 I2 -- Kc'' QN Kc of the upper state
62- 63 I2 -- s1 QN sigma_1
68- 69 I2 -- J' QN J of the lower state
70- 71 I2 -- Ka' QN Ka of the lower state
72- 73 I2 -- Kc' QN Kc of the lower state
74- 75 I2 -- s2 QN sigma_2
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Note (1): prediction up to J=80 and 1 THz. Hyperfine splitting
(maximum splitting ∼500kHz) is NOT included.
Note (2): output using the CALPGM/SPCAT format. Documentation can be found in
https://spec.jpl.nasa.gov/ftp/pub/calpgm/spinv.pdf
Note (3): logInt & Gup calculated using reduced spin weight of 8, and
partition function 353614.251 at 300K. To get full spin weight of 6 H-atoms
multiply the GUP and partition function simultaneously by 8.
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Acknowledgements:
Luyao Zou, luyao.zou(at)lisa.ipsl.fr
(End) Luyao Zou [Univ. Lille], Patricia Vannier [CDS] 18-Jan-2023