J/A+A/620/A184 HSCO+ and DSCO+ lines (Lattanzi+, 2018)
HSCO+ and DSCO+: a multi-technique approach in the laboratory for the
spectroscopy of interstellar ions.
Lattanzi V., Spezzano S., Laas J.C., Chantzos J., Bizzocchi L., Lee K.L.K.,
McCarthy M.C., Caselli P.
<Astron. Astrophys. 620, A184 (2018)>
=2018A&A...620A.184L 2018A&A...620A.184L (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Radio lines
Keywords: molecular data - methods: laboratory: molecular -
techniques: spectroscopic - radio lines: ISM
Abstract:
Protonated molecular species have been proven to be abundant in the
interstellar gas. This class of molecules is also pivotal for the
determination of important physical parameters for the ISM evolution
(e.g. gas ionisation fraction) or as tracers of non-polar, hence not
directly observable, species. The identification of these molecular
species through radioastronomical observations is directly linked to a
precise laboratory spectral characterisation.
The goal of the present work is to extend the laboratory measurements
of the pure rotational spectrum of the ground electronic state of
protonated carbonyl sulfide (HSCO+) and its deuterium substituted
isotopomer (DSCO+). At the same time, we show how implementing
different laboratory techniques allows the determination of different
spectroscopical properties of asymmetric-top protonated species.
Three different high-resolution experiments were involved to detected
for the first time the b-type rotational spectrum of HSCO+, and to
extend, well into the sub-millimeter region, the a-type spectrum of
the same molecular species and DSCO+. The electronic ground-state of
both ions have been investigated in the 273-405GHz frequency range,
allowing the detection of 60 and 50 new rotational transitions for
HSCO+ and DSCO+, respectively.
The combination of our new measurements with the three rotational
transitions previously observed in the microwave region permits the
rest frequencies of the astronomically most relevant transitions to be
predicted to better than 100kHz for both HSCO+ and DSCO+ up to
500GHz, equivalent to better than 60m/s in terms of equivalent
radial velocity. The present work illustrates the importance of using
different laboratory techniques to spectroscopically characterise a
protonated species at high frequency. Each instruments addressed
complementary part of the same spectroscopic challenge, showing that a
similar approach can be adopted in the future when dealing with
similar reactive species.
Description:
The measurements were performed using three different instruments: the
CASAC (Center for Astrochemical Studies Absorption Cell) spectrometer
a newly millimeter wave Free Jet Unit experiment, both at the
Max-Planck-Institut fuer extraterrestrische Physik , and a Fourier
Transform Microwave spectrometer equipped with a double-resonance
extensions, at the Harvard-Smithsonian Center for Astrophysics.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 71 63 Assignments, measured line positions and estimated
experimental uncertainty for the analysed
transitions of HSCO+
table2.dat 71 53 Assignments, measured line positions and estimated
experimental uncertainty for the analysed
transitions of DSCO+
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat 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
17- 18 I2 --- J Lower state J
21- 22 I2 --- Ka Lower state Ka
25- 26 I2 --- Kc Lower state Kc
41- 51 F11.4 MHz Obs Measured line position
57- 61 F5.3 MHz unc Assumed uncertainty
68- 71 A4 --- Ref Reference (1)
--------------------------------------------------------------------------------
Note (1): References as follows:
MT07 = McCarthy & Thaddeus, Journal of Chemical Physics, 127, 221104 (2007)
TW = this work
--------------------------------------------------------------------------------
Acknowledgements:
Valerio Lattanzi, lattanzi(at)mpe.mpg.de
(End) Patricia Vannier [CDS] 22-Oct-2018