J/A+A/602/A34 HOCO+ and DOCO+ rest frequencies (Bizzocchi+, 2017)
Accurate sub-millimetre rest frequencies for HOCO+ and DOCO+ ions.
Bizzocchi L., Lattanzi V., Laas J., Spezzano S., Giuliano B.M.,
Prudenzano D., Endres C., Sipilae O., Caselli P.
<Astron. Astrophys. 602, A34 (2017)>
=2017A&A...602A..34B 2017A&A...602A..34B (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics
Keywords: molecular data - methods: laboratory: molecular -
techniques: spectroscopic - radio lines: ISM
Abstract:
HOCO+ is a polar molecule that represents a useful proxy for its
parent molecule CO2, which is not directly observable in the cold
interstellar medium. This cation has been detected towards several
lines of sight, including massive star forming regions, protostars,
and cold cores. Despite the obvious astrochemical relevance,
protonated CO2 and its deuterated variant, DOCO+, still lack an
accurate spectroscopic characterisation.
The aim of this work is to extend the study of the ground-state pure
rotational spectra of HOCO+ and DOCO+ well into the sub-millimetre
region.
Ground-state transitions have been recorded in the laboratory using a
frequency-modulation absorption spectrometer equipped with a
free-space glow-discharge cell. The ions were produced in a
low-density, magnetically confined plasma generated in a suitable gas
mixture. The ground-state spectra of HOCO+ and DOCO+ have been
investigated in the 213-967GHz frequency range; 94 new rotational
transitions have been detected. Additionally, 46 line positions taken
from the literature have been accurately remeasured.
The newly measured lines have significantly enlarged the available
data sets for HOCO+ and DOCO+, thus enabling the determination of
highly accurate rotational and centrifugal distortion parameters. Our
analysis shows that all HOCO+ lines with Ka≥3 are perturbed by a
ro-vibrational interaction that couples the ground state with the v5=1
vibrationally excited state. This resonance has been explicitly
treated in the analysis in order to obtain molecular constants with
clear physical meaning.
The improved sets of spectroscopic parameters provide enhanced lists
of very accurate sub-millimetre rest frequencies of HOCO+ and DOCO
Description:
The spectra described in this work have been recorded with the
frequency-modulation (FM) sub-millimetre absorption spectrometer
recently developed at the Center for Astrochemical Studies
(Max-Planck-Institut fur extraterrestrische Physik) in Garching.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 97 93 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of HOCO+
table2.dat 82 84 Assignments, measured line positions and
least-squares residuals for the analysed
transitions of DOCO+
table3.dat 86 57 Predicted rest frequencies, estimated accuracies
and lines strenghts for the ground vibrational
state of HOCO+
table4.dat 86 72 Predicted rest frequencies, estimated accuracies
and lines strenghts for the ground vibrational
state of DOCO+
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Byte-by-byte Description of file (#): table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 4 I2 --- J' Upper state J
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' ?=- Upper state Kc
13 A1 --- n_Kc' [*] * for unresolved asymmetry doublet
17- 18 I2 --- J Lower state J
21- 22 I2 --- Ka Lower state Ka
25- 26 I2 --- Kc ?=- Lower state Kc
27 A1 --- n_Kc [*] * for unresolved asymmetry doublet
40- 50 F11.4 MHz Obs Measured line position
54- 60 F7.4 MHz O-CfitI ? Least-squares residual (fit I) (1)
69- 75 F7.4 MHz O-CfitII Least-squares residual (fit II)
82- 86 F5.3 MHz unc Assumed uncertainty
94- 97 A4 --- Ref Reference (G1)
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Note (1): An empty field indicates that the line is not considered in fit I.
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Byte-by-byte Description of file (#): table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
3- 4 I2 --- J' Upper state J
7- 8 I2 --- Ka' Upper state Ka
11- 12 I2 --- Kc' ?=- Upper state Kc
13 A1 --- n_Kc' [*] * for unresolved asymmetry doublet
17- 18 I2 --- J Lower state J
21- 22 I2 --- Ka Lower state Ka
25- 26 I2 --- Kc ?=- Lower state Kc
27 A1 --- n_Kc [*] * for unresolved asymmetry doublet
40- 50 F11.4 MHz Obs Measured line position
55- 61 F7.4 MHz O-C Least-squares residual
68- 72 F5.3 MHz unc Assumed uncertainty
80- 82 A3 --- Ref Reference
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Byte-by-byte Description of file (#): table3.dat table4.dat
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Bytes Format Units Label Explanations
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4- 5 I2 --- J' Upper state J
7 A1 --- --- [(]
8- 9 I2 --- Ka' Upper state Ka
10 A1 --- --- [,]
11- 12 I2 --- Kc' Upper state Kc
13 A1 --- --- [)]
21- 22 I2 --- J Lower state J
24 A1 --- --- [(]
25- 26 I2 --- Ka Lower state Ka
27 A1 --- --- [,]
28- 29 I2 --- Kc Lower state Kc
30 A1 --- --- [)]
39- 48 F10.3 MHz RestFreq Rest frequency
50 A1 --- --- [(]
51- 52 I2 kHz e_RestFreq Estimated error on RestFreq
53 A1 --- --- [)]
57- 65 E9.4 D+2 Strength Transition strength
69- 74 F6.3 cm-1 Eupper Upper state energy
78- 86 E9.4 s-1 Acoeff Einstein's A coefficient
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Global notes:
Note (G1): References as follows:
TW = this work
B86 = Bogey et al., 1986, J. Chem. Phys., 84, 10
B88 = Bogey et al., 1988, J. Mol. Struct., 190, 465
OE96 = Ohshima & Endo, 1996, Chem. Phys. Lett., 256, 635
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Acknowledgements:
Luca Bizzocchi, bizzocchi(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 02-Apr-2017