J/A+A/577/A91 Millimeter wave spectrum of vinyl acetate (Kolesnikova+, 2015)
Laboratory millimeter wave spectrum and astronomical search for vinyl acetate.
Kolesnikova L., Pena I., Alonso J.L., Cernicharo J., Tercero B., Kleiner I.
<Astron. Astrophys. 577, A91 (2015)>
=2015A&A...577A..91K 2015A&A...577A..91K
ADC_Keywords: Interstellar medium; Spectroscopy; Atomic physics
Keywords: astrochemistry - ISM: molecules - submillimeter: ISM -
astronomical databases: miscellaneous - line: identification -
ISM: individual objects: Orion KL
Abstract:
The recent discovery of methyl acetate in Orion KL makes vinyl
acetate, CH3-(C=O)-O-CH=CH2, a potential molecule in the interstellar
medium.We obtained very accurate spectroscopic constants in a
comprehensive laboratory analysis of its rotational spectra which can
be used to predict those transition frequencies towards interstellar
sources.
We present the experimental study and theoretical analysis of the
ground torsional state of vinyl acetate in a large spectral range for
astrophysical use.
The room-temperature rotational spectrum of vinyl acetate has been
measured from 125 to 305GHz to provide direct frequencies to the
astronomical community. Additional measurements have also been made
using a broadband CP-FTMWspectrometer in the region of 6 - 18 GHz.
Transition lines, corresponding to the most stable conformer, have
been observed and assigned. All the rotational transitions revealed
the A-E splitting due to the methyl internal rotation and had to be
treated with a specific internal rotation code (BELGI-Cs).
We analyzed 2508 transitions up to J"=75 for vt=0 for the most stable
conformer of vinyl acetate. The new lines were globally fitted with
previously published data and 24 parameters of the Hamiltonian were
accurately determined. The spectral features of vinyl acetate were
then searched for in Orion KL. Using the whole line survey of Orion KL
(80-280GHz) obtained with the IRAM 30m radio telescope we can
provide only an upper limit to the column density of vinyl acetate.
However, using the ALMA Science Verification data we obtain a
tentative detection of this species that will require further search
at other frequencies to confirm its presence in this high mass star
forming region.
Description:
Assignments, observed frequencies, and calculated frequencies from the
RAM fit, line strengths, and energies of the lower and upper energy
levels for vinyl acetate in vt=0 torsional state included in the fit
with parameters of Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 24 Molecular constants in the ρ-axis system of
vinyl acetate [CH3-(C=O)-O-CH=CH2] obtained from
the global fit using program BELGI-Cs
table2.dat 103 2508 Assignments, observed frequencies, and calculated
frequencies from the RAM fit, line strengths,
and energies of the lower and upper energy levels
included in the fit with parameters of Table 1
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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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1- 16 A16 --- Cst Constant label (1)
18- 25 A8 --- Unit Unit
27- 60 A34 --- Operator Operator (2)
62- 74 F13.7 --- Value Value of the parameter from the present fit
77- 84 F8.7 --- e_Value Error on value (statistical uncertainty)
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Note (1): All constants refer to the ρ-axis system; therefore, the inertia
tensor is not diagonal and the constants cannot be directly compared to
those of the principal axis system.
Note (2): Ja , Jb , Jc are the components of the overall rotation angular
momentum, Jγ is the angular momentum of the internal rotor rotating
around the internal rotor axis by an angle γ, and {u,v} is the
anti commutator uv+vu. The product of the constant and operator from a
given row yields the term actually used in the vibration-rotation-torsion
Hamiltonian, except for F, ρ, and A, which occur in the Hamiltonian
in the form F(Jγ-ρJa)2+AJ2a.
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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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1- 3 I3 --- J1 [1/75] Upper J quantum number
4- 6 I3 --- Ka1 [-16/16] Upper Ka quantum number (1)
7- 9 I3 --- Kc1 [0/75] Upper Kc quantum number
12 A1 --- p1 [±] Parity (1)
14- 16 I3 --- J0 [0/75] Lower J quantum number
17- 19 I3 --- Ka0 [-15/15] Lower Ka quantum number (1)
20- 22 I3 --- Kc0 [0/74] Lower Kc quantum number
25 A1 --- p0 [±] Parity (1)
29- 38 F10.3 MHz FreqO [6044/329556] Observed transition frequency
41- 42 I2 kHz e_FreqO [5/50] Uncertainty of the experimentally
measured line
46- 55 F10.3 MHz FreqC [6044/329556] Calculated transition frequency
58- 59 I2 kHz e_FreqC [0/40] Calculated uncertainty of the transition
frequency
62- 67 F6.3 MHz O-C [-0.24/0.19] Observed minus calculated frequency
71- 77 F7.3 D2 Smu2 [0/175] Calculated line strength
82- 89 F8.4 cm-1 E1 [39/452] Upper level energy
92- 99 F8.4 cm-1 E0 [0/407] Lower level energy (2)
103 I1 --- Ref [1/3] Source of the data (3)
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Note (1): Torsion-rotation levels of the A species have a "parity" p label;
levels of the E species have a signed Ka value. We note that for
certain degenerate transitions, the sum of line strengths of the
degenerate transitions for a given cluster is preserved.
Note (2): Lower state energy relative to the J"=K"=0 (A species) level at
39.3666cm-1 which is set to zero.
Note (3): References as follows:
1 = this study
2 = Nguyen, H. V. L., Jabri, A., Van, V., & Stahl, W. 2014,
J. Phys. Chem. A, 118, 12130
3 = Velino, B., Maris, A., Melandri, S., & Caminati, W. 2009, J. Mol.
Spectrosc., 256, 228
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Acknowledgements:
Lucie Kolesnikova, lucie.kolesnikova(at)uva.es
(End) Lucie Kolesnikova [GEM, UVa, Spain], Patricia Vannier [CDS] 10-Apr-2015