J/A+A/644/A123 Rotational spectroscopy of CH2OH (Chitarra+, 2020)
Reinvestigation of the rotation-tunneling spectrum of the CH2OH radical.
Accurate frequency determination of transitions of astrophysical interest up to
330 GHz.
Chitarra O., Martin-Drumel M-A., Gans B., Loison J-C., Spezzano S.,
Lattanzi V., Mueller H.S.P., Pirali O.
<Astron. Astrophys. 644, A123 (2020)>
=2020A&A...644A.123C 2020A&A...644A.123C (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio lines ;
Spectroscopy
Keywords: methods, laboratory, molecular - techniques, spectroscopic -
catalogs - ISM: molecules - submillimeter: general
Abstract:
The hydroxymethyl radical (CH2OH) is one of the two structural
isomers, together with the methoxy radical (CH3O), that can be
produced by abstraction of a hydrogen atom from methanol (CH3OH). In
the interstellar medium (ISM), both CH2OH and CH3O are suspected
to be intermediate species in many chemical reactions, including those
of formation and destruction of methanol. The determination of the
CH3O/CH2OH ratio in the ISM would bring important information
concerning the formation processes of these species in the gas and
solid phases. Interestingly, only CH3O has been detected in the ISM
so far, despite the recent first laboratory measurement of the CH2OH
rotation-tunneling spectrum. This lack of detection is possibly due to
the non-observation in the laboratory of the most intense
rotational-tunneling transitions at low temperature.
To support further searches for the hydroxymethyl radical in space, we
have performed a thorough spectroscopic study of its
rotation-tunneling spectrum, with particular focus on transitions
involving the lowest quantum numbers of the species.
We have recorded the rotation-tunneling spectrum of CH2OH at room
temperature in the millimeter-wave domain using a frequency
multiplication chain spectrometer associated to a fluorine-induced
H-abstraction method. The radical was produced from methanol
precursor.
About 180 transitions were observed including those involving the
lowest N and Ka quantum numbers, predicted intense under cold
astrophysical conditions. These transitions were fitted together with
available millimeter-wave lines from the literature. The systematic
observation of all components of the rotational transitions yields a
large improvement of the spectroscopic parameters which now allow
confident searches of the hydroxymethyl radical in cold to warm
environments of the ISM.
Description:
All files used for the initial and final fits of the
submillimeter-wave data for CH2OH and with SPFIT and SPCAT.
Detailled explanations on SPFIT/ SPACT could be found at
https://www.astro.uni-koeln.de/cdms/pickett
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
ch2ohini.cat 87 6140 Initial prediction up to 1000GHz
ch2ohini.bak 80 38 Initial .bak file, input file for SFIPT
ch2ohini.fit 147 307 Initial .fit file, input file for SFIPT
ch2ohini.int 63 4 Initial .int file, input file for SFIPT
ch2ohini.lin 97 88 Initial .lin file, input file for SFIPT
ch2ohini.par 80 38 Initial .par file, input file for SFIPT
ch2ohini.var 80 76 Initial .var file, input file for SFIPT
ch2oh.cat 87 4871 New prediction up to 1000GHz
ch2oh.bak 80 43 New .bak file, input file for SFIPT
ch2oh.fit 147 524 New .fit file, input file for SFIPT
ch2oh.int 61 4 New .int file, input file for SFIPT
ch2oh.lin 104 278 New .lin file, input file for SFIPT
ch2oh.par 80 43 New .par file, input file for SFIPT
ch2oh.var 80 91 New .var file, input file for SFIPT
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Byte-by-byte Description of file: ch2oh.cat ch2ohini.cat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 13 F11.4 MHz Freq Frequency of the line
14- 21 F8.4 MHz e_Freq Estimated or experimental error
23- 29 F7.4 [nm2.MHz] logInt Base 10 logarithm of the integrated
intensity in units of nm2.MHz
31 I1 --- DOF Degrees of freedom in the rotational
partition function
33- 41 F9.4 --- ELow Lower state energy in wavenumbers
43- 44 I2 --- gup Upper state degeneracy
47- 55 I9 --- Tag Species tag or molecular identifier
56- 57 I2 --- N" Upper N quantum number
59 I1 --- Ka" Upper Ka quantum number
60- 61 I2 --- Kc" Upper Kc quantum number
63 I1 --- v" Upper v quantum number
64- 65 I2 --- J" Upper J quantum number
66- 67 I2 --- F1" Upper F1 quantum number
69 I1 --- IH" Upper IH quantum number
70- 71 I2 --- F" Upper F quantum number
72- 73 I2 --- N' Lower N quantum number
75 I1 --- Ka' Lower Ka quantum number
76- 77 I2 --- Kc' Lower Kc quantum number
79 I1 --- v' Lower v quantum number
80- 81 I2 --- J' Lower J quantum number
82- 83 I2 --- F1' Lower F1 quantum number
85 I1 --- IH' Lower IH quantum number
86- 87 I2 --- F' Lower F quantum number
--------------------------------------------------------------------------------
Description of file:
File ch2oh_ini.lin (initial measured transition):
------------------------------------------------------------------------------
Bytes Format Units Label Explanations
------------------------------------------------------------------------------
2- 4 I2 --- N" Upper N quantum number
6 I1 --- Ka" Upper Ka quantum number
8- 10 I2 --- Kc" Upper Kc quantum number
12 I1 --- v" Upper v quantum number
14- 16 I2 --- J" Upper J quantum number
17- 19 I2 --- F1" Upper F1 quantum number
21 I1 --- I"H Upper IH quantum number
23- 25 I2 --- F" Upper F quantum number
26- 28 I2 --- N' Lower N quantum number
30 I1 --- Ka' Lower Ka quantum number
32- 34 I2 --- Kc' Lower Kc quantum number
36 I1 --- v' Lower v quantum number
38- 40 I2 --- J' Lower J quantum number
41- 43 I2 --- F1' Lower F1 quantum number
45 I1 --- IH' Lower IH quantum number
47- 49 I2 --- F' Lower F quantum number
51- 61 F13.6 MHz Freq Observed transition frequency
63- 67 F7.5 MHz unc Uncertainty of measurements (1)
69- 73 F6.3 --- WT relative weight when 2 lines are assigned
to one frequency (1)
70- 92 A11 --- LABEL Transition label delimited by /
when no relative weight
76- 98 A11 --- LABEL Transition label delimited by /
when relative weight is given
------------------------------------------------------------------------------
Note (1): When two different transitions are assigned to the same frequency,
a relative weight is given for each component.
------------------------------------------------------------------------------
File ch2oh.lin (final measured transition):
------------------------------------------------------------------------------
Bytes Format Units Label Explanations
------------------------------------------------------------------------------
2- 4 I2 --- N" Upper N quantum number
6 I1 --- Ka" Upper Ka quantum number
8- 10 I2 --- Kc" Upper Kc quantum number
12 I1 --- v" Upper v quantum number
14- 16 I2 --- J" Upper J quantum number
17- 19 I2 --- F1" Upper F1 quantum number
21 I1 --- IH" Upper IH quantum number
23- 25 I2 --- F" Upper F quantum number
26- 28 I2 --- N' Lower N quantum number
30 I1 --- Ka' Lower Ka quantum number
32- 34 I2 --- Kc' Lower Kc quantum number
36 I1 --- v' Lower v quantum number
38- 40 I2 --- J' Lower J quantum number
41- 43 I2 --- F1' Lower F1 quantum number
45 I1 --- IH' Lower IH quantum number
47- 49 I2 --- F' Lower F quantum number
53- 63 F13.6 MHz Freq Observed transition frequency
70- 74 F7.5 MHz unc Uncertainty of measurements (1)
75- 80 F6.3 --- WT relative weight when 2 lines are assigned
to one frequency (1)
77- 90 A11 --- LABEL Transition label delimited by /
when no relative weight (2)
81- 94 A11 --- LABEL Transition label delimited by /
when relative weight is given (2)
------------------------------------------------------------------------------
Note (1): When two different transitions are assigned to the same frequency,
a relative weight is given for each component.
Note (2): Transitions used from a previous work are indicated by /Bermudez2017
------------------------------------------------------------------------------
File ch2oh_ini.par, ch2oh_par (spectroscopic parameters):
First 3 lines for SFIPT use (see https://www.astro.uni-koeln.de/cdms/pickett)
For lines 4 to 38:
------------------------------------------------------------------------------
Bytes Format Units Label Explanations
------------------------------------------------------------------------------
4- 14 I10 --- IDPAR coding of the parameter
15- 38 E22.15 --- PAR parameter value
39- 54 E14.8 --- ERPAR parameter uncertainty
55- 65 A11 --- LABEL parameter label that is delimited by /
------------------------------------------------------------------------------
Acknowledgements:
Olivia Chitarra , olivia.chitarra(at)universite-paris-saclay.fr
References:
Bermudez et al., 2017A&A...598A...9B 2017A&A...598A...9B,
Laboratory detection of the rotational-tunnelling spectrum of the
hydroxymethyl radical, CH2OH
(End) Patricia Vannier [CDS] 12-Nov-2020