J/ApJS/205/9 Rotational transition frequencies of HCOOCH3 (Kobayashi+, 2013)
The microwave spectroscopy of methyl formate in the second torsional excited
state.
Kobayashi K., Takamura K., Sakai Y., Tsunekawa S., Odashima H., Ohashi N.
<Astrophys. J. Suppl. Ser., 205, 9 (2013)>
=2013ApJS..205....9K 2013ApJS..205....9K
ADC_Keywords: Spectroscopy ; Interstellar medium ; Atomic physics
Keywords: catalogs - molecular data - submillimeter: ISM -
techniques: spectroscopic
Abstract:
The cis-methyl formate molecule (HCOOCH3) is a well known molecule
found in interstellar space. Recently, rotational lines of methyl
formate in the first CH3 torsional excited state were observed in
Orion KL and W51e2. It is quite natural to observe methyl formate in
even higher vibrational states considering the temperature estimated
in Orion KL and W51e2. Maeda et al. (2008JMoSp.251..293M 2008JMoSp.251..293M) reported
results on the laboratory spectroscopy of methyl formate including the
spectral analysis in its second CH3 torsional state. Their
assignments were limited to a series of a-type R-branch lines and low
Ka b-type R-branch transitions, and many assigned lines are excluded
in the least-squares analysis. In the present study, we extended the
line assignments of both the A- and E-species transitions in the
second CH3 torsional state especially in the frequency region below
the 120GHz region. By combining the present assignments and those made
by Maeda et al., 1951 transitions in total for the second CH3
torsional state, 1096 A-species transitions up to J=39, and Ka=15
and 855 E-species transitions up to J=35 and Ka=13, were
least-squares analyzed by using the pseudo-principal-axis-method
Hamiltonian with 42 parameters consisting of rotational, centrifugal
distortion, and internal rotational constants in the second CH3
torsional state. In addition, 1012 transitions out of 1096 A-species
transitions could also be least-squares analyzed by using Watson's
A-reduced Hamiltonian with 43 parameters, which can serve to calculate
the energy levels of the A-species lines of molecules with the CH3
internal rotation conveniently.
Description:
We have carried out an experiment to supplement the frequency range to
include 215-235GHz without gap and to take some additional data in the
59-268GHz region with our source-modulation spectrometer.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 59 1953 Pure rotational transition frequencies of
cis-methyl formate in vt=2 analyzed by using
the pseudo-principal-axis-method-(PAM) Hamiltonian
model (Ohashi et al. 2004JMoSp.227...28O 2004JMoSp.227...28O)
table3.dat 56 1012 Pure rotational A-sublevel transition frequencies
of cis-methyl formate in vt=2 analyzed by using
Watson's A-reduced Hamiltonian (Equation (5))
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See also:
J/A+A/538/A119 : Spectrum of 18O-methyl formate (HCO18OCH3)
(Tercero+ 2012)
J/ApJS/190/315 : Rotational spectrum of H13COOCH3 (Carvajal+, 2010)
J/A+A/500/1109 : Rotational spectrum of HCOO13CH3 (Carvajal+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 A1 --- S [AE] Symmetry: the A or E torsional substates
3- 4 I2 --- J' [2/40] The upper J quantum number
6- 7 I2 --- Ka' [0/15] The upper Ka quantum number
9- 10 I2 --- Kc' [0/37] The upper Kc quantum number
12- 13 I2 --- J" [1/39] The lower J quantum number
15- 16 I2 --- Ka" [0/15] The lower Ka quantum number
18- 19 I2 --- Kc" [0/34] The lower Kc quantum number
21- 31 F11.3 MHz Freq [-168772.5/378357.1] The experimental frequency
of the transition
32 A1 --- f_Freq [*] The * shows the transitions not included
34- 39 F6.3 MHz O-C [-0.23/0.44] The observed minus calculated value
41- 48 F8.4 cm-1 El [0.4105/347.948] The lower state energy (G1)
50- 54 F5.2 D+2 Smu2 [0.07/89.51] The line strength (see equation (6))
56- 59 A4 --- Ref The source of measurement (G2)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- J' [2/35] The upper J quantum number
4- 5 I2 --- Ka' [0/13] The upper Ka quantum number
7- 8 I2 --- Kc' [0/35] The upper Kc quantum number
10- 11 I2 --- J" [1/34] The lower J quantum number
13- 14 I2 --- Ka" [0/13] The lower Ka quantum number
16- 17 I2 --- Kc" [0/34] The lower Kc quantum number
19- 29 F11.3 MHz Freq [-108498.4/378357.1] The experimental frequency
of the transition
31- 36 F6.3 MHz O-C [-0.28/0.244] The observed minus calculated value
38- 45 F8.4 cm-1 El [0.4105/217.274] The lower state energy (G1)
47- 51 F5.2 D+2 Smu2 [0.09/90.1] The line strength (see equation (6))
53- 56 A4 --- Ref The source of measurement (G2)
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Global notes:
Note (G1): The relative energy to the lowest rotational level
of A-symmetry in vt=2.
Note (G2): Code as follows:
MAEI = measurement of Maeda et al.(2008JMoSp.251..293M 2008JMoSp.251..293M), assignment made by
Maeda et al., used in the least squares analysis of Maeda et al.
MAEO = measurement of Maeda et al.(2008JMoSp.251..293M 2008JMoSp.251..293M), assignment made by
Maeda et al., not used in the least squares analysis of Maeda et al.
TYMI = measurement of Maeda et al.(2008JMoSp.251..293M 2008JMoSp.251..293M) was replaced by the
measurement in the present study, assignment made by Maeda et al.,
used in the least squares analysis of Maeda et al.
TYMO = measurement of Maeda et al.(2008JMoSp.251..293M 2008JMoSp.251..293M) was replaced by the
measurement in the present study, assignment made by Maeda et al.,
not used in the least squares analysis of Maeda et al.
TYAM = measurement at the University of Toyama,
assignment made for the first time in the present study.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-Mar-2013