J/ApJ/808/21 Methyl acetate (CH3COOCH3) rotational transitions (Das+, 2015)
Methyl acetate and its singly deuterated isotopomers in the interstellar medium.
Das A., Majumdar L., Sahu D., Gorai P., Sivaraman B., Chakrabarti S.K.
<Astrophys. J., 808, 21 (2015)>
=2015ApJ...808...21D 2015ApJ...808...21D (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Models
Keywords: astrochemistry; evolution; ISM: abundances; ISM: molecules;
methods: numerical
Abstract:
Methyl acetate (CH3COOCH3) has been recently observed by the IRAM
30m radio telescope in Orion, though the presence of its deuterated
isotopomers is yet to be confirmed. We therefore study the properties
of various forms of methyl acetate, namely, CH3COOCH3,
CH2DCOOCH3, and CH3COOCH2D. Our simulation reveals that these
species could be produced efficiently in both gas and ice phases.
Production of methyl acetate could follow radical-radical reaction
between acetyl (CH3CO) and methoxy (CH3O) radicals. To predict
abundances of CH3COOCH3 along with its two singly deuterated
isotopomers and its two isomers (ethyl formate and hydroxyacetone), we
prepare a gas-grain chemical network to study the chemical evolution
of these molecules. Since gas-phase rate coefficients for methyl
acetate and its related species are unknown, either we consider
similar rate coefficients for similar types of reactions (by following
existing databases) or we carry out quantum chemical calculations to
estimate the unknown rate coefficients. For the surface reactions, we
use adsorption energies of reactants from some earlier studies.
Moreover, we perform quantum chemical calculations to obtain spectral
properties of methyl acetate in infrared and sub-millimeter regions.
We prepare two catalog files for the rotational transitions of
CH2DCOOCH3 and CH3COOCH2D in JPL format, which could be useful
for their detection in regions of interstellar media where
CH3COOCH3 has already been observed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table8.dat 66 216 Rotational transitions for gas phase CH3COOCH2D
table9.dat 66 210 Rotational transitions for gas phase CH2DCOOCH3
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See also:
J/A+A/564/A82 : Microwave spectra of CH3CHCCHCN (Carles+, 2014)
J/A+A/562/A56 : Cyanomethyl anion & deuterated derivatives (Majumdar+, 2014)
J/A+A/558/A6 : 2-pentynenitrile (C2H5CCCN) microwave spectrum (Carles+, 2013)
J/ApJ/770/L13 : Detection of CH3COOCH3 in Orion (Tercero+, 2013)
Byte-by-byte Description of file: table[89].dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 MHz Freq [6870/295215.3] Calculated frequency
14- 20 F7.4 [nm2.MHz] logI [-9/-3.4] Log integrated intensity at 300K
22 I1 --- DoF [3] Degrees of freedom (1)
24- 31 F8.4 cm-1 ELow [0/207] Lower state energy (2)
33- 34 I2 --- gup [1/89] Upper state degeneracy (3)
36- 40 I5 --- Tag [74003] Molecule tag
42- 44 I3 --- QnF [304] Coding for the quantum number format (4)
46- 47 I2 --- QnFup1 [1/43] First upper state quantum number
49 I1 --- QnFup2 [0] Second upper state quantum number
51- 52 I2 --- QnFup3 [1/43] Third upper state quantum number
54- 55 I2 --- QnFup4 [0/44] Fourth upper state quantum number
57- 58 I2 --- QnFlow1 [0/42] First lower state quantum number
60 I1 --- QnFlow2 [0] Second lower state quantum number
62- 63 I2 --- QnFlow3 [0/42] Third lower state quantum number
65- 66 I2 --- QnFlow4 [0/43] Fourth lower state quantum number
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Note (1): In the rotational partition function (0 for atoms, 2 for
linear molecules, 3 for non linear molecules).
Note (2): Relative to the lowest energy level in the ground vibrionic state.
Note (3): gup = gI * gN , where gI is the spin statistical weight and
gN = 2N + 1 the rotational degeneracy.
Note (4): QnF = 100 * Q + 10 * H + NQn where NQn is the number of quantum
numbers for each state, H indicates the number of half integer
quantum numbers, Qmod5, the residual when Q is divided by 5, gives
the number of principal quantum numbers (without the spin
designating ones).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Nov-2015