J/A+A/520/A64 Trans-HCOOH hyperfine structure (Cazzoli+, 2010)
Hyperfine structure in the rotational spectra of trans-formic acid:
Lamb-dip measurements and quantum-chemical calculations.
Cazzoli G., Puzzarini C., Stopkowicz S., Gauss J.
<Astron. Astrophys. 520, A64 (2010)>
=2010A&A...520A..64C 2010A&A...520A..64C
ADC_Keywords: Atomic physics
Keywords: methods: laboratory - techniques: spectroscopic - ISM: molecules -
submillimeter: ISM - radio lines: ISM - molecular data
Abstract:
Formic acid, HCOOH, is the simplest organic acid and the first that
has been identified in the interstellar medium. Its astrophysical
relevance has motivated this spectroscopic study.
The aim of this investigation is to provide very accurate rest
frequencies for the trans isomer of HCOOH as well as to improve the
spectroscopic and hyperfine parameters available in the literature for
this molecule.
The Lamb-dip technique has been exploited in order to record the
rotational spectrum of trans-HCOOH at sub-Doppler resolution in the
millimeter- and submillimeter-wave frequency ranges and, when
possible, to resolve the hyperfine structure due to the hydrogen
nuclei. THz measurements have been carried out as well. The
experimental investigation has been supported by high-level
quantum-chemical calculations.
Description:
Table S1 reports our measurements, along with those from Chardon et
al. (1976, J. Chem. Phys., 64, 1434). Together with the transition
frequencies and the corresponding uncertainties, the observed -
calculated differences from the Fit 1 (see manuscript) are given.
Table S2 reports the complete set of quantum-chemical results as
obtained by employing different basis sets. All elements of the
spin-rotation and spin-spin tensors are reported. Equilibrium values
and vibrational corrections are given.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tables1.dat 71 435 Transition frequencies and fit residuals
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Byte-by-byte Description of file: tables1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- J Rotational quantum number of the lower
rotational level
4- 5 I2 --- Ka Rotational quantum number of the lower
rotational level
7- 8 I2 --- Kc Rotational quantum number of the lower
rotational level
10- 11 I2 --- F1 ? Hyperfine quantum number of the lower
rotational level
13- 14 I2 --- F ? Hyperfine quantum number of the lower
rotational level
19- 20 I2 --- J" Rotational quantum number of the upper
rotational level
22- 23 I2 --- Ka" Rotational quantum number of the upper
rotational level
25- 26 I2 --- Kc" Rotational quantum number of the upper
rotational level
28- 29 I2 --- F1" ? Hyperfine quantum number of the upper
rotational level
31- 32 I2 --- F" ? Hyperfine quantum number of the upper
rotational level
40- 52 F13.5 MHz Freq Transition frequency
54- 59 F6.5 MHz e_Freq rms uncertainty on Freq
61- 67 F7.2 kHz O-C Observed-calculated frequency
71 A1 --- Ref [CP] Reference for data (1)
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Note (1): Reference as follows:
C = Chardon et al. (1976, J. Chem. Phys., 64, 1434)
P = Present investigation
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Table S2: Basis-set investigation and vibrational corrections for the hyperfine
parameters of trans-HCOOH (kHz), with all reported calculations
performed at the CCSD(T) level.
| Basis set | C_aa | C_bb | C_cc | C_ab | C_ba |
|||||||
Equilibrium values (1) | | | | |
H(C) | cc-pCVTZ | -7.612 | 1.077 | -0.912 | -0.222 | 1.354 |
| cc-pCVQZ | -7.556 | 1.097 | -0.896 | -0.216 | 1.373 |
| cc-pCV5Z | -7.537 | 1.102 | -0.893 | -0.211 | 1.377 |
Vibrational corrections | | | | |
H(C) | cc-pCVTZ | +0.522 | -0.058 | +0.076 | +0.076 | -0.065 |
Equilibrium values (1) | | | | |
H(O) | cc-pCVTZ | -7.558 | 0.834 | -1.466 | 0.073 | -1.938 |
| cc-pCVQZ | -7.381 | 0.850 | -1.435 | 0.086 | -1.867 |
| cc-pCV5Z | -7.328 | 0.858 | -1.423 | 0.090 | -1.852 |
Vibrational corrections | | | | |
H(O) | cc-pCVTZ | +0.390 | -0.088 | +0.105 | +0.009 | +0.303 |
|||||||
| Basis set | D_aa | D_bb | D_cc | Dab=Dba |
|||||_|
Equilibrium values (1)| | | | |
H(C)-H(O) | -- b | 3.157 | -8&678 | 5&521 | -5&792 |
Vibrational corrections | | | |
H(C)-H(O) | cc-pVTZ | -0.078 | +0&205 | -0&127 | +0&137 |
H(C)-H(O) | cc-pCVTZ | -0.079 | +0&207 | -0&128 | +0&138 |
|||||_|
Definitions:
H(C): computed values for spin-rotation (SR) constants of H bonded to C
H(O): computed values for spin-rotation (SR) constants of H bonded to O
H(C)-H(O): computed values for spin-spin (SS) constants of H-H
Notes:
(1): Computed at the semi-experimental geometry (Demaison et al., 2007,
J. Chem. Phys., 126, 164305).
b: The equilibrium values of the D^HH tensor elements depend only on
molecular structure (see text).
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Acknowledgements:
Cristina Puzzarini, cristina.puzzarini(at)unibo.it
(End) Patricia Vannier [CDS] 28-Jun-2010