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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file tables1.dat 71 435 Transition frequencies and fit residuals
Byte-by-byte Description of file: tables1.dat
Bytes Format Units Label Explanations
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)
Note (1): Reference as follows: C = Chardon et al. (1976, J. Chem. Phys., 64, 1434) P = Present investigation
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). Acknowledgements: Cristina Puzzarini, cristina.puzzarini(at)unibo.it
(End) Patricia Vannier [CDS] 28-Jun-2010
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