Spectroscopy of a low global warming power refrigerant. Infrared and millimeter-wave spectra of trifluoroethene (HFO-1123) in the ground and some vibrational excited states☆
Introduction
In the last decades, great attention has been devoted to the search for suitable replacements of the gases used for domestic and industrial purposes which strongly contribute to the atmospheric pollution, the ozone hole and the greenhouse effect. Unsaturated hydrofluoroolefins (HFO’s) are an interesting alternative to chlorofluorocarbons (CFC’s). Indeed, such molecules have a very short atmospheric lifetime, an almost zero Ozone Depletion Potential (ODP) and a low Global Warming Potential (GWP) [1].
The search of an ideal candidate for refrigerants is nowadays a crucial issue, considering that recent studies showed that a very limited number of fluids exhibit the required environmental properties [2]. 1,1,2,-trifluoroethene (CF2=CHF, HFO-1123, hereafter referred as TFE) is used nowadays in heat pumps and conditioning systems, often in mixtures with difluoromethane (CH2F2, HFC-32). In these mixtures self-decomposition does not occur [1]; also, they have low toxicity and are only mildly flammable [1], [3], proving therefore to be a valuable alternative to R-410A, a common refrigerant with high GWP.
The atmospheric importance of CF2=CHF has stimulated a number of spectroscopic studies in the past. Low resolution infrared (IR) spectra were first recorded by Mann et al. [4] and later by McKean [5]. In 2002 Jiang et al. [6] calculated the vibrational fundamental wavenumbers and the relative intensities using the Scaled Quantum Mechanical (SQM) force field procedure in combination with the hybrid three-parameter B3-PW91 density functional. Microwave transitions of the ground and some vibrationally excited states were reported a long time ago by Bhaumik et al. [7] and Wellington Davis & Gerry [8].
More recently, Leung & Marshall recorded rotational transitions of TFE between 6 and 22 GHz by Fourier transform (FT) spectroscopy for the most abundant isotopologue and the two singly 13C-substituted species. From the determined spectroscopic constants they also derived the structural parameters of the molecule [9]. High-resolution infrared studies are however limited to the very strong fundamentals ν3, ν4, and ν5 in the atmospheric window, centered at 1360, 1265, and 1173 cm respectively. These high-resolution spectra were recorded with a tunable diode laser and analysed by Visinoni et al. [10], [11], [12]. The authors pointed out the presence of several resonances and determined some parameters for the interacting states.
The infrared atmospheric window has been only partially analysed and this work aims to a more complete spectroscopic characterization of this region and of the low-lying vibrational states. The goal is to provide the necessary laboratory data useful for the atmospheric detection of this molecule. The infrared spectrum was recorded at high resolution (0.004 cm) by FT-IR spectroscopy between 500 and 1500 cm where the ν3, ν4, ν5, ν6 (929 cm), ν7 (623 cm) and ν10 (750 cm) fundamental bands are located with the objective to assign and analyse for the first time ν6, ν7, and ν10 and to re-investigate ν3, ν4, and ν5. Given the complexity of the ro-vibrational structure, in this paper we focused only on the ν6 fundamental vibrational band and on the detection of pure rotational transitions in the ground state and in the low energy and excited vibrational states. The rotational spectra were recorded in the frequency ranges 80–96 GHz and 245–260 GHz using a frequency-modulation millimeter-wave spectrometer.
In this work we present therefore a combined rotational and ro-vibrational investigation from which very accurate spectroscopic parameters were determined for the ground state and the investigated excited vibrational states.
Section snippets
Millimeter spectrometer
Rotational spectra were recorded in the frequency ranges 80–96 GHz and 245–260 GHz using a frequency-modulation millimeter-wave spectrometer [13], [14]. The radiation source is a Gunn diode (J.E. Carlstrom Co.) emitting in the spectral range 80–115 GHz with an output power up to 50 mW. A passive multiplier (WR3.4X2, Virginia Diodes) is used to reach the higher frequencies. The diode’s radiation is phase-locked to a harmonic of a digital frequency synthesizer (HP8672A, 2–18 GHz) and its
General features
From a spectroscopic point of view, trifluoroethene is a planar near-prolate asymmetric-top molecule belonging to the Cs symmetry point group, having an asymmetry parameter . The molecular geometry of TFE with respect to its principal axes is shown in Fig. 2.
Its permanent electric dipole moment ((6) D) lies in the ab plane, with the b component ((6) D) much greater than that of the a component ((15) D) [7]. Of the 12 fundamentals, all infrared active, 9 are
Discussion
The fitting procedure, the spectral simulation and the calculation of the ro-vibrational term values were carried out by employing the ATIRS software [21] and the SPFIT/SPCAT program suite [22]. The rotational and ro-vibrational data were analysed in a global fit together with the literature data for the ground state only [7], [8], [9]. The transition frequencies of Ref. [7] relative to vibrationally excited states were not used in our global fit, not only because they are less precise than our
Conclusions
In this paper we report the detection of the rotational spectrum of TFE in the ground and in the vibrationally excited states and . Moreover, the fundamental ν6 ro-vibrational band has been observed. All the data were analysed in a global fit and sets of spectroscopic parameters for each state were determined in the A-reduction scheme. The quality of the fit is very good, as shown by the values of the statistical errors, the precision of the parameters
CRediT authorship contribution statement
Filippo Tamassia: Conceptualization, Validation, Methodology, Investigation, Resources, Writing - review & editing, Supervision, Project administration. Mattia Melosso: Conceptualization, Validation, Formal analysis, Investigation, Data curation, Writing - original draft, Visualization, Supervision, Project administration. Luca Dore: Software, Writing - review & editing, Resources, Funding acquisition. Michele Pettini: Investigation, Formal analysis. Elisabetta Canè: Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This study was supported by Bologna University (RFO funds), MIUR (Project PRIN 2015: STARS in the CAOS, Grant number 2015F59J3R), and Ca’ Foscari University, Venice (AdiR funds).
References (23)
CH stretching frequencies, bond lengths and strengths in halogenated ethylenes
Spectrochim Acta Part A
(1975)- et al.
The microwave spectrum and structure of trifluoro-ethylene
J Mol Struct
(1973) - et al.
Centrifugal distortion in trifluoroethylene
J Mol Spectrosc
(1984) - et al.
The infrared laser spectrum of CF2=CHF near 1360 cm: rovibrational analysis of the ν3 fundamental
J Mol Spectrosc
(1995) - et al.
High-resolution infrared measurements and analysis of the ν4 band of CF2=CHF
J Mol Spectrosc
(1997) - et al.
Diode laser spectroscopy of trifluoroethylene in the 8.6-µm region
J Mol Spectrosc
(1998) - et al.
The pure rotational spectrum of 15ND2 observed by millimetre and submillimetre-wave spectroscopy
J Quant Spectrosc Ra
(2019) - et al.
The HITRAN2016 molecular spectroscopic database
J Quant Spectrosc Ra
(2017) Low-resolution microwave spectroscopy: a new band type
J Mol Spectrosc
(1975)The millimeter-wave rotational spectrum of chlorobenzene: analysis of centrifugal distortion and of conditions for oblate-type bandhead formation
J Mol Spectrosc
(1990)
Cited by (6)
High resolution FTIR spectrum of CH<inf>2</inf>D<sup>37</sup>Cl: ν<inf>4</inf> and ν<inf>8</inf> fundamental bands
2023, Journal of Quantitative Spectroscopy and Radiative TransferHigh resolution FTIR study of the ν<inf>5</inf>, ν<inf>6</inf>, and ν<inf>9</inf> fundamental bands of CH<inf>2</inf>D<sup>37</sup>Cl
2021, Journal of Quantitative Spectroscopy and Radiative TransferCitation Excerpt :Evidence of CH2D35Cl impurities were observed and identified in the infrared spectra of the sample. The infrared spectra of CH2D37Cl were recorded at the University of Bologna (Italy) using a Bomem DA3.002 FTIR spectrometer [23,24] equipped with a globar source, a KBr beamsplitter and a photoconductive mercury cadmium telluride (MCT) detector. The high-resolution (0.004 cm−1 unapodized) spectra were recorded at room temperature with sample pressure of 31 Pa and 53 Pa and an optical pathlength of 6 m, achieved with a multipass absorption cell.
Extensive ro-vibrational analysis of deuterated-cyanoacetylene (DC<inf>3</inf>N) from millimeter-wavelengths to the infrared domain
2020, Journal of Quantitative Spectroscopy and Radiative TransferIn Vitro and In Silico Vibrational-Rotational Spectroscopic Characterization of the Next-Generation Refrigerant HFO-1123
2022, Journal of Physical Chemistry AHigh-Resolution Infrared Spectroscopy of DC<inf>3</inf>N in the Stretching Region
2021, Frontiers in Astronomy and Space Sciences
- ☆
Supplementary material available.