J/ApJ/796/36 PH2CN/CH3PH2 rotational transition frequency (Halfen+, 2014)
Millimeter/submillimeter spectroscopy of PH2CN(∼X 1A') and
CH3PH2(∼X 1A'): probing the complexity of interstellar phosphorus
chemistry.
Halfen D.T., Clouthier D.J., Ziurys L.M.
<Astrophys. J., 796, 36 (2014)>
=2014ApJ...796...36H 2014ApJ...796...36H (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Interstellar medium ; Spectra, millimetric/submm
Keywords: astrochemistry - ISM: molecules - line: identification -
methods: laboratory: molecular - molecular data
Abstract:
Millimeter/submillimeter spectra of PH2CN(~{X} 1A') and
CH3PH2(~{X} 1A') have been recorded for the first time
using direct absorption techniques. This work extends previous
measurements of both molecules beyond the 10-50 GHz range. Both
species were created in the presence of an AC discharge by the
reaction of phosphorus vapor and either cyanogen and hydrogen
(PH2CN) or methane (CH3PH2). Twelve rotational transitions of
PH2CN were recorded over the region 305-422 GHz for asymmetry
components Ka=0 through 8. For CH3PH2, eight rotational
transitions were measured from 210-470 GHz with Ka=0 through 16;
these spectra exhibited greater complexity due to the presence of
internal rotation, which splits the Ka=1, 2, and 3 asymmetry
components into A and E states. Combined analyses of the
millimeter/submillimeter and previous microwave data were performed
for both molecules. For PH2CN, the spectra were fit with a
Watson S-reduced asymmetric top Hamiltonian, resulting in more
accurate rotational and centrifugal distortion constants. In the case
of CH3PH2, an asymmetric top internal-rotation Hamiltonian was
employed in the analysis, significantly improving the rotational and
torsional parameters over previous microwave estimates. Searches for
both molecules were subsequently conducted toward Sgr B2(N), using the
12 m telescope of the Arizona Radio Observatory (ARO). Neither species
was identified, with abundance upper limits, relative to H2, of
f(PH2CN/H2)<7.0x10-12 and f(CH3PH2/H2)<8.4x10-12.
The nitrogen analogs NH2CN and CH3NH2 are therefore more
abundant in Sgr B2(N) by factors of >2 and >200, respectively.
Description:
The astronomical searches for PH2CN and CH3PH2 were based on a
spectral-line survey of Sgr B2(N), conducted from 2002 September to
2013 March at the facilities of the Arizona Radio Observatory (ARO),
covering the 1, 2, and 3 mm atmospheric windows (68-116, 130-172,
and 210-280 GHz: D. T. Halfen et al. 2014, in preparation). Only
data from the 2 and 3 mm bands, obtained at the ARO 12 m telescope at
Kitt Peak, Arizona, were examined in this study. The receivers used
were dual-channel, cooled SIS mixers, tuned single-sideband with image
rejection typically ≥18 dB. Data were also taken using a new
dual-polarization receiver, utilizing ALMA Band 3 (83-116 GHz)
sideband-separating (SBS) mixers with typical image rejection ≥16 dB,
achieved within the mixer assembly.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 43 204 Rotational Transition Frequencies of
PH2CN(~{X} 1A');
Nitrogen hyperfine collapsed
table2.dat 43 398 Rotational Transition Frequencies
of CH3PH2(~{X} 1A')
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See also:
J/ApJS/117/427 : Sgr B2 spectral survey (Nummelin+, 1998)
Byte-by-byte Description of file: table1.dat table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- J' [1/40] Upper J component
4- 6 I3 --- Ka' [-16/16] Upper Ka component
8- 9 I2 --- Kc' [0/40] Upper Kc component
11- 12 I2 --- J" [0/39] Lower J component
14- 16 I3 --- Ka" [-16/16] Lower Ka component
18- 19 I2 --- Kc" [0/39] Lower Kc component
21 A1 --- A/E A/E state
23- 32 F10.3 MHz nuObs Observed frequency
34 A1 --- f_nuObs [a] Flag on nuObs (1)
36- 41 F6.3 MHz O-C ? Observed minus calculated frequencies
43 A1 --- f_O-C [b] Flag on O-C (2)
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Note (1): Flag as follows:
a = From Kojima et al. (1961, JCP, 35, 2139).
Note (2): Flag as follows:
b = Blended line; not included in fit.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 31-May-2017