Journal of Quantitative Spectroscopy and Radiative Transfer
Collision induced broadening of ν1 band and ground state spectral lines of sulfur dioxide perturbed by N2 and O2
Introduction
Nowadays, remote sensing techniques allow monitoring and accurately retrieving the concentration profiles of atmospheric constituents and trace pollutants, since these molecules have strong rotation and vibration-rotation absorptions in the microwave (MW) and infrared (IR) spectral domains, respectively [1], [2], [3], [4]. The satellites used for sounding the terrestrial atmosphere embark spectrometers that provide a large amount of spectral information at ever increasing quality in terms of spectral coverage, resolution and signal-to-noise ratio [1]. For these reasons, spectroscopic parameters are of fundamental importance for exploiting remote sensing applications in atmospheric and climate research, environmental monitoring and gas-phase analysis. As a matter of fact, only their accurate knowledge allows an retrieval of concentrations and distributions of the gas phase molecular species in the atmosphere. The relevant spectroscopic parameters include line-by-line parameters, i.e., transition frequencies and their intensities, pressure broadening coefficients and pressure induced shifts, and their temperature dependence. The existing spectroscopic data are then collected into a number of different databases, among which the most important ones are HITRAN [5], GEISA [6], JPL [7], and the Cologne database [8]. Within this framework, the aim of laboratory spectroscopy is to provide spectroscopic parameters for a wide variety of species of atmospheric, astrophysical and industrial relevance. Furthermore the study of collisional broadening and shifting coefficients, these being related to the intermolecular potential, can shed light on the driving forces ruling the scattering events in the gas phase (see e.g. [9], [10], [11], [12], [13] and references therein).
Sulfur dioxide (SO2) is an important molecule for Earth atmosphere since it actively enters in the sulfur cycle and it is one of the causes of acid rains. SO2 has a lifetime in the atmosphere of about a day, it is oxidized quickly, thus leading to aerosol formation and acid deposition [14]. As sulfate, it is an important component of fine aerosol particles (PM10 and PM2.5). Furthermore, sulfate aerosol also affects Earth's radiation balance either thorough direct scattering of sunlight or indirectly via modification of cloud albedoes. On a global scale, the majority of natural SO2 is produced by volcanoes [15], [16], [17] and by the oxidation of sulfur gases produced by the decomposition of plants. Therefore, natural emissions usually occur at high altitude or far from city centers, and hence the SO2 background concentration in clear air is about 1 ppb [18]. On the other hand, a sizeable amount of SO2 is of anthropogenic origin, being produced by combustion of fossil fuels as well as by non-ferrous smelting processes for the conversion of ores to free metals [18]. In addition, this compound is largely employed in food-preserving and wine making industries. It is thus not surprising that SO2 has received a great deal of attention from the scientific community and it is still the subject of a number of spectroscopic studies.
The fundamental ν1 and ν3 bands of 32S16O2 isotopologue have been thoroughly analyzed in 1980s by Guelachvili and co-workers [19], [20] and subsequently reinvestigated by Flaud et al. together with the ν2 fundamental and the 2ν2 − ν2 hot band [21]. In 2005 Müller and Brünker have accurately re-determined the rotational parameters for the ground and v2 = 1 states [22]. Some ro-vibrational transitions, belonging to ν1 and ν3 bands, have been object of study by Sumpf with the aim of determining line-by-line transition intensities [23], while accurate intensity determinations have been performed within the spectral region 940–1400 cm−1 region by Fourier transform IR spectroscopy [24]. Since 1992 different studies have focused on the determination of SO2 self- [23], [25], [26], [27], [28], [29], [30], [31], [32] and foreign-broadening coefficients [26], [27], [33], [34], [35], [36], [37]. A few years ago, a complete listing of sulfur dioxide self-broadening coefficients has been compiled by combining the results obtained from IR and MW spectroscopy with semiclassical calculations [38]. In addition, the homodimer of SO2 has been investigated by Tasinato and Grimme, theoretically using dispersion-corrected density functional theory (DFT-D3) as well as experimentally by means of tunable diode laser (TDL) IR spectroscopy [39]. In that work, the dissociation energies of (SO2)2 and (CH2F2)2 have been determined experimentally from the broadening of the ro-vibrational transitions of the corresponding monomers collisionally perturbed by a range of damping gases [39]. Recently, SO2 has been included in an HITRAN-like database of line parameters for molecules of planetary interest perturbed by H2, He or CO2 [40]. Very recently, Ceselin et al. exploited IR and mm-/sub-mm wave spectroscopy to retrieve new line-by-line pressure broadening parameters of SO2 perturbed by He, H2 and CO2 [41].
In the present contribution, our work aiming at the determination of SO2 broadening parameters for atmospheric and astrochemical applications is extended by considering the atmospherically relevant N2 and O2 buffer gases.
Section snippets
Experimental details
The broadening parameters of SO2 perturbed by N2 and O2 as buffer gases have been determined both in the infrared (IR) and millimeter/sub-millimeter (mm-/sub-mm) wave region. IR measurements have been carried out at the Laboratory of Molecular Spectroscopy of Venice (LMS-Ve), whereas mm-/sub-mm ones have been performed in the Laboratory of mm-/sub-mm wave Spectroscopy of Bologna (LMS-Bo).
For what concerns IR measurements, SO2 high resolution spectra were recorded by using a TDL spectrometer
Results and discussion
The radiating species investigated in the present work is an asymmetric near-prolate rotor belonging to the C2v symmetry point group. It has three vibrational normal modes: ν1 and ν3 correspond to the OSO symmetric and asymmetric stretching, respectively, while ν2 represents the bending motion. The ν1 fundamental belongs to the A1 symmetry species and it gives rise to a B-type band located at about 1151.7 cm−1. The presence of two identical oxygen nuclei (zero nuclear spin) allows, for all
Conclusions
In the present work, a line-by-line list of SO2 foreign-broadening coefficients has been retrieved by the analysis of several ro-vibrational transitions belonging to the 32S16O2 ν1 band (in the 8.8 µm region) as well as a number of pure rotational transitions of the vibrational ground state (in the mm-/sub-mm wave range), with O2 and N2 as damping gases. In addition, 10 transitions of the ν1 + ν2 − ν2 32S16O2 hot band and 6 lines belonging to ν1 of 34S16O2 have also been analyzed in the IR region.
Acknowledgments
The present work has been financially supported by MIUR (PRIN 2012 funds for project "STAR: Spectroscopic and computational Techniques for Astrophysical and atmospheric Research"), Università Ca' Foscari Venezia (ADiR funds), University of Bologna (RFO funds) and Scuola Normale Superiore (funds for project COSMO: "Combined experimental and computational spectroscopic modeling for astrochemical applications"). GC thanks Università Ca' Foscari Venezia for her research fellowship.
References (58)
- et al.
The 2015 edition of the GEISA spectroscopic database
J Mol Spectrosc
(2016) - et al.
Submillimeter, millimeter, and microwave spectral line catalogue
JQSRT
(1998) - et al.
The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC
J Mol Spectrosc
(2016) - et al.
Analysis of the ν1 and ν3 absorption bands of 32S16O2
J Mol Spectrosc
(1984) - et al.
Analysis of the SO2 absorption Fourier spectrum in the regions 1055 to 2000 and 2200 to 2550 cm-1
J Mol Spectrosc
(1987) - et al.
Reanalysis of the (010), (020), (100), and (001) rotational levels of 32S16O2
J Mol Spectrosc
(1993) Line intensity and self-broadening investigations in the ν1 and ν3 bands of SO2
J Mol Struct
(2001)- et al.
Line intensities for the 8-µm bands of SO2
J Mol Spectrosc
(1998) - et al.
Line broadening in the ν3 band of SO2: studied with diode laser spectroscopy
J Mol Spectrosc
(1992) - et al.
Self-, air-, and nitrogen-broadening in the ν1 band of SO2
J Mol Spectrosc
(1996)
Self- and air-broadening in the ν3 band of SO2
J Mol Spectrosc
Study of SO2 line parameters with a quantum cascade laser spectrometer around 1090 cm-1: comparison with calculations of the ν;1 and ν;1 + ν;2 – ν;2 bands of 32SO2 and the ν;1 band of 34SO2
JQSRT
Revised molecular parameters for 32SO2 and 34SO2 from high resolution study of the infrared spectrum in the 7–8 µm wavelength region
JQSRT
The pressure broadening of SO2 by N2, O2, He, and H2 between 90 and 500 K
JQSRT
Noble gas pressure-induced broadening and shift of H2O and SO2 absorption lines
J Mol Spectrosc
N2-, O2-, H2-, and He-broadening of SO2 rotational lines in the mm-/submm-wave and THz frequency regions: the J and Ka dependence
JQSRT
N2-, O2- and He-collision-induced broadening of sulfur dioxide ro-vibrational lines in the 9.2 µm atmospheric window
Spectrochim Acta A
A complete listing of sulfur dioxide self-broadening coefficients for atmospheric applications by coupling infrared and microwave spectroscopy to semiclassical calculations
JQSRT
H2, He and CO2 line-broadening coefficients, pressure shifts and temperature-dependence exponents for the HITRAN database. Part 1: SO2, NH3, HF, HCl, OCS and C2H2
JQSRT
The Lamb-dip spectrum of methylcyanide: precise rotational transition frequencies and improved ground state rotational parameters
J Molec Spectrosc
Lineshape measurements of rotational lines in the millimeter-wave region by second harmonic detection
J Molec Spectrosc
Using Fast Fourier Transform to compute the line shape of frequency-modulated spectral profiles
J Molec Spectrosc
A comparison of lineshape models in the analysis of modulated and natural rotational line profiles: application to the pressure broadening of OCS and CO
J Molec Spectrosc
Infrared HCN lineshapes as a test of galatry and speed-dependent voigt profiles
J Molec Spectrosc
Experimental determination of air-broadening parameters of pure rotational transitions of HNO3: intercomparison of measurements by using different techniques
J Mol Spectrosc
Intercomparison between ozone broadening parameters retrieved from millimetre-wave measurements by using different techniques
J Mol Spectrosc
Experimental and theoretical investigation on pressure-broadening and pressure-shifting of the 22.2 GHz line of water
JQSRT
Galatry versus speed-dependent Voigt profiles for millimeter lines of O3 in collision with N2 and O2
J Mol Spectrosc
Remote sensing of the atmosphere for environmental security
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Rovibrational spectra of Ar–SO<inf>2</inf> and (SO<inf>2</inf>)<inf>2</inf> van der Waals complexes in the v<inf>1</inf> region of SO<inf>2</inf>
2022, Journal of Molecular SpectroscopyCitation Excerpt :Up to now, a large number of experimental and theoretical studies have been devoted to determining its accurate spectroscopic parameters like line positions [5–6], line intensities [7–9] and broadening coefficients [10–28]. The quantum number and temperature dependence of broadening coefficients of SO2 have been studied on self-broadened [10–17] or perturbed by N2 [10–11,19–22], O2 [20–22], H2 [21,23–25], He [19–21,24–25], CO2 [24–27] and Ne, Ar, Kr and Xe [23,28]. Theoretical calculations on the line-broadening coefficients were usually based on the semi-classical theory [20].
Line-by-line spectroscopic parameters of HFC-32 ro-vibrational transitions within the atmospheric window around 8.2 μm
2018, Journal of Molecular SpectroscopyExpert List of Absorption Lines of the <sup>32</sup>S<sup>16</sup>O<inf>2</inf> Molecule in the 0–4200 cm<sup>–1</sup> Spectral Region
2023, Atmospheric and Oceanic Optics