Publications

Publications pertinent to our current work.

(* indicates system of known or potential atmospheric interest.)

Review articles

• *Smith, C.J.; Huff, A.K.; Ward, R.M, Carboxylic Sulfuric Anhydrides, J. Phys. Chem. A 2020, 124, 601-612. https://pubs.acs.org/doi/full/10.1021/acs.jpca.9b09310
• *Leopold, K. R. Hydrated Acid Clusters. Annu. Rev. Phys. Chem. 2011, 62, 327-349. https://www.annualreviews.org/doi/pdf/10.1146/annurev-physchem-032210-103409
• Leopold, K.R.; Canagaratna, M.; Phillips, J.A., Partially Bonded Molecules from the Solid State to the Stratosphere. Acc. Chem. Res. 1997, 20, 57-64. https://pubs.acs.org/doi/10.1021/ar950115l
• Leopold, K.R. Partially Bonded Molecules and Their Transition to the Crystalline State in Advances in Molecular Structure Research, Vol II., edited by Hargittai, M. and Hargittai, I., JAI Press: Greenwich, CT, pp. 103-127 (1996).
• Leopold, K.R.; Fraser, G.T.; Novick, S.E.; Klemperer, W., Current Themes in Microwave and Infrared Spectroscopy of Weakly Bound Complexes. Chem. Rev.1994, 94, 1807-1827. https://pubs.acs.org/doi/10.1021/cr00031a004

Carboxylic Sulfuric Anhydrides

• Love, N.; Carpenter, C.A.; Huff, A.K.; Douglas, C.J.; Leopold, K.R., A Microwave and Computational Study of Pivalic Sulfuric Anhydride and the Pivalic Acid Monomer: Mechanistic Insights into the RCOOH + SO₃ Reaction, J. Phys. Chem A, 2022,126, 6194-6202. https://pubs.acs.org/doi/10.1021/acs.jpca.2c04904
• *Smith, C.J.; Huff, A.K.; Ward, R.M, Carboxylic Sulfuric Anhydrides, J. Phys. Chem. A 2020, 124, 601-612. https://pubs.acs.org/doi/full/10.1021/acs.jpca.9b09310
• Huff, A.K.; Mackenzie, R.B.; Smith, C.J.; Leopold, K.R. A Perfluorinated Carboxylic Sulfuric Anhydride” Microwave and Computational Studies of CF₃COOSO₂OH, J. Phys. Chem. A 2019, 123, 2237-2243. https://pubs.acs.org/doi/10.1021/acs.jpca.9b00300
• *Smith, C.J.; Huff, A.K.; Mackenzie, R.B.; Leopold, K.R. Hydration of and Acid Anhydride: The Water Complex of Acetic Sulfuric Anhydride, J. Phys. Chem. A 2018, 122, 4549-4554. https://pubs.acs.org/doi/10.1021/acs.jpca.8b02432
• *Smith, C.J.; Huff, A.K.; Mackenzie, R.B.; Leopold, K.R., Observation of Two Conformers of Acrylic Sulfuric Anhydride by Microwave Spectroscopy, J. Phys. Chem. A 2017, 121, 9074-9080. https://pubs.acs.org/doi/10.1021/acs.jpca.7b09833
• *Huff, A.K.; Mackenzie, R.B.; Smith, C.J.; Leopold, K.R., Facile Formation of Acetic Sulfuric Anhydrides: Microwave Spectrum, Internal Rotation, and Theoretical Calculations, J. Phys. Chem. A 2017, 121, 5659-5664. https://pubs.acs.org/doi/full/10.1021/acs.jpca.7b05105
• *Mackenzie, R. B.; Dewberry, C. T.; Leopold, K. R., Gas phase Observation and Microwave Spectroscopic Characterization of Formic Sulfuric Anhydride. Science 2015, 349, 58-61. https://www.science.org/doi/10.1126/science.aaa9704

Hydrogen Bonding & Proton Transfer

• Reynolds, A.J.; Leopold, K.R., "Partial Proton Transfer in the Gas Phase: A Spectroscopic and Computational Analysis of the Trifluoroacetic Acid  Trimethylamine Complex", J. Phys. Chem A, in press.
• Huff, A.K.; Love, N.; Leopold, K.R., Microwave Study of Triflic Acid Hydrates: Evidence for the Transition from Hydrogen-Bonded Clusters to a Microsolvated Ion Pair, J. Phys. Chem. A 2021, 125, 8033-8046. https://pubs.acs.org/doi/10.1021/acs.jpca.1c06815
• Love, N.; Huff, A.K.; Leopold, K.R., Proton Transfer in a Bare Superacid-Amine Complex: A Microwave and Computational Study of Trimethylammonium Triflate, J. Phys. Chem. A 2021, 125, 5061-5068. https://pubs.acs.org/doi/10.1021/acs.jpca.1c03345
• *Mackenzie, R.B.; Dewberry, C.T.; Leopold, K.R., The Trimethylamine – Formic Acid Complex: Microwave Characterization of a Prototype for Potential Precursors to Atmospheric Aerosol, J. Phys. Chem. A 2016, 120, 2268-2273. https://pubs.acs.org/doi/10.1021/acs.jpca.6b01500
• Mackenzie, R. B.; Dewberry, C. T.; Leopold, K. R., The Formic Acid - Nitric Acid Complex: Microwave Spectrum, Structure and Proton Transfer, J. Phys. Chem. A. 2014, 118, 7975-7985. https://pubs.acs.org/doi/10.1021/jp507060w
• Sedo, G.; Leopold, K. R., Partial Proton Transfer in a Molecular Complex: Assessments From Both the Donor and Acceptor Points of View, J. Phys. Chem. A 2011, 115, 1787–1794. https://pubs.acs.org/doi/full/10.1021/jp108851t
• *Sedo, G.; Doran, J. L.; Leopold, K. R., Partial Proton Transfer in the Nitric Acid Trihydrate Complex. J. Phys. Chem. A 2009, 113, 11301–11310. https://pubs.acs.org/doi/full/10.1021/jp9063033
• *Craddock, M. B.; Brauer, C. S.; Leopold, K. R., Microwave Spectrum, Structure, and Internal Dynamics of the Nitric Acid Dihydrate Complex, J. Phys. Chem. A 2008, 112, 488–496. https://pubs.acs.org/doi/10.1021/jp075789f
• *Brauer, C. S.; Sedo, G.; Leopold, K. R., Dipole Moment of the H₂SO₄-H₂O Complex. Geophys. Res. Lett. 2006, 33, L23805. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006GL028110
• Brauer, C. S.; Craddock, M. B.; Kilian, J.; Grumstrup, E. M.; Orilall, M. C.; Mo, Y.; Gao, J.; Leopold, K.R. Amine-Hydrogen Halide Complexes: Experimental Electric Dipole Moments and a Theoretical Decomposition of Dipole Moments and Binding Energies. J. Phys. Chem. A 2006, 110, 10025–10034. https://pubs.acs.org/doi/10.1021/jp062101a
• Hunt, S.W.; Higgins, K.J.; Craddock, M.B.; Brauer, C.S.; Leopold, K.R., Influence of a Polar Near-Neighbor on Incipient Proton Transfer in a Strongly Hydrogen Bonded Complex. J. Am. Chem. Soc. 2003, 125, 13850-13860. https://pubs.acs.org/doi/10.1021/ja030435x
• *Fiacco, D.L.; Hunt, S.W.; Leopold, K.R., Microwave Investigation of Sulfuric Acid Monohydrate. J. Am. Chem. Soc. 2001, 105, 4504-4511. https://pubs.acs.org/doi/10.1021/ja012724w
• *Ott, M.E.; Leopold, K.R., A Microwave Study of the Ammonia – Nitric Acid Complex. J. Phys. Chem. A 1999, 103, 1322-1328. https://pubs.acs.org/doi/10.1021/jp9841891
• *Canagaratna, M.; Ott, M.E.; Leopold, K.R., The Nitric Acid – Water Complex: Microwave Spectrum, Structure, and Tunneling, J. Phys. Chem. A 1998, 102, 1489-1497. https://pubs.acs.org/doi/10.1021/jp980033p

Experimental Methods and Data Analysis

• Love, N.: Huff, A.K.; Leopold, K.R., A New Program for the Assignment and Fitting of Dense Rotational Spectra Based on Spectral Progressions: Application to the Microwave Spectrum of Pivalic Anhydride, J. Mol. Spectrosc. 2020, 370, 111294. https://www.sciencedirect.com/science/article/pii/S002228522030062X
• Dewberry, C. T.; Mackenzie, R. B.; Leopold, K. R., 3D-Printed Slit Nozzles for Fourier Transform Microwave Spectroscopy. Rev. Sci. Instrumen. 2015, 86, 065107. https://aip.scitation.org/doi/10.1063/1.4922852
• Leopold, K. R. Generalized Equations for the Inertial Tensor of a Weakly Bound Complex. J. Mol. Spectrosc. 2012, 278, 27–30. https://www.sciencedirect.com/science/article/pii/S0022285212001269
• Hunt, S.W.; Brauer, C.S.; Craddock, M.B.; Higgins, K.J.; Nienow, A.M.; Leopold, K.R., Microwave Observation of H₃N-SO₃∙∙∙H₂O Using a Concentric, Dual-Injection Nozzle Source. Chem. Phys. 2004, 305, 155-164. https://www.infona.pl/resource/bwmeta1.element.elsevier-fb5c9a37-4fdf-39c6-847d-9542725462c6

Partially Bonded Molecules

• Sedo, G.; Leopold, K. R., Microwave spectrum of (CH₃)₃ CCN–SO₃. J. Mol. Spectrosc. 2010, 262, 135-138.
•  https://www.sciencedirect.com/science/article/pii/S0022285210001128
• Brauer, C. S.; Craddock, M. B.; Higgins, K. J.; Leopold, K. R., Microsolvation of a Partially Bonded Complex by Non-polar and Weakly Polar Microsolvents: A Microwave and Ab Initio Study of HCN–SO₃–Ar and HCN–SO₃–CO. Mol. Phys. 2007, 105, 613–25.  https://www.tandfonline.com/doi/abs/10.1080/00268970701194335?cookieSet=1
• Craddock, M.B.; Brauer; C.S.; Higgins, K.J.; Leopold, K.R., A Microwave and Ab Initio Investigation of N₂-SO₃, OC-SO₃, and OC-SO₃-Ar. J. Mol. Spectrosc. 2003, 222, 63-73. https://www.sciencedirect.com/science/article/pii/S0022285202000838
• Fiacco, D.L.; Leopold, K.R., Partially Bound Systems as Sensitive Probes of Microsolvation: A Microwave and ab initio Study of HCN···HCN-BF₃. J. Phys. Chem. A 2003, 107, 2808-2814. https://pubs.acs.org/doi/10.1021/jp022245z
• Hunt, S.W.; Fiacco, D.L.; Craddock, M.; Leopold, K.R., Correlation of Dative Bond Length and Donor Proton Affinity in Adducts of SO₃: A Good Predictor for HCCCN-SO₃. J. Mol. Spectrosc. 2002, 212, 213-218.  https://www.sciencedirect.com/science/article/pii/S0022285202985541
• Hunt, S.W., and Leopold, K.R. Molecular and Electronic Structure of C₅H₅N-SO₃: Correlation of Ground State Physical Properties with Orbital Energy Gaps in Partially Bound Lewis Acid-Base Complexes. J. Phys. Chem. A 2001, 105, 5498-5506. https://pubs.acs.org/doi/10.1021/jp010460u
• Fiacco, D.L., Mo, Y., Hunt, S.W., Roberts, A., and Leopold, K.R. Dipole Moments of Partially Bound Lewis Acid-Base Adducts. J. Phys. Chem. A 2001, 105, 484-493. https://pubs.acs.org/doi/10.1021/jp0031810
• Fiacco, D.L.; Hunt, S.W.; Leopold, K.R., Structural Change at the Onset of Microsolvation: Rotational Spectroscopy of HCN···HCN SO₃. J. Phys. Chem. A 2000, 104, 8323-8327. https://pubs.acs.org/doi/10.1021/jp001983p
• Fiacco, D.L.; Toro, A.; Leopold, K.R., Structure, Bonding, and Dipole Moment of (CH₃)₃N-SO₃. A Microwave Study. Inorg. Chem. 2000, 39 37-43. https://pubs.acs.org/doi/10.1021/ic990925j
• Burns, W.A.; Phillips, J.A.; Canagaratna, M.; Goodfriend, H.; Leopold, K.R. Partially Formed Bonds in HCN-SO₃ and CH₃CN-SO₃: A Comparison between Donor-Acceptor Complexes of SO₃ and BF₃. J. Phys. Chem. A 1999, 103, 7445-7453. https://pubs.acs.org/doi/10.1021/jp991646k
• Canagaratna, M.; Phillips, J.A.; Goodfriend, H.; Fiacco, D.L.; Ott, M.E.; Harms, B.; Leopold, K.R., Structures of the van der Waals Isomers of Halosulfuric Acids: Microwave Spectra of HX-SO₃ (X=F,Cl, Br). J. Mol. Spectrosc. 1998, 192, 338-347. https://pubmed.ncbi.nlm.nih.gov/9831500/
• Canagaratna, M.; Ott, M.E.; Leopold, K.R., Determination of the Dipole Moment of H₃N-SO₃ in the Gas Phase, Chem. Phys. Lett.1997, 281, 63-68. https://www.sciencedirect.com/science/article/pii/S0009261497012207
• Phillips, J.A.; Britton, D.; Leopold, K.R., Gas – Solid Structure Differences in the Donor – Acceptor Complex (CH₃)₂HN-SO₂. J. Chem. Crystallogr. 1996, 26, 533-538. https://link.springer.com/article/10.1007/BF01668411
• Canagaratna, M.; Phillips, J.A.; Goodfriend, H.; Leopold, K.R. Structure and Bonding of the Sulfamic Acid Zwitterion: Microwave Spectrum of ⁺NH₃-SO₃^–. J. Am. Chem. Soc. 1996, 118, 5290-5295. https://pubs.acs.org/doi/10.1021/ja953983m
• Hankinson, D.J.; Almlöf, J.; Leopold, K.R., A Direct Comparison Between Structure Correlations and Reaction Paths. J. Phys. Chem. 1996, 100, 6904-6909. https://pubs.acs.org/doi/full/10.1021/jp960353d
• Phillips, J.A.; Canagaratna, M.; Goodfriend H.; Grushow, A.; Almlöf, J.; Leopold, K.R., Microwave and Ab Initio Investigation of HF-BF₃. J. Am. Chem. Soc. 1995, 117, 12549-56. https://pubs.acs.org/doi/10.1021/ja00155a018
• *Phillips, J.A.; Canagaratna, M.; Goodfriend, H.; Leopold, K.R., Microwave Detection of a Key Intermediate in the Formation of Atmospheric Sulfuric Acid: The Structure of H₂O-SO₃. J. Phys. Chem. 1995, 99, 501-504. https://pubs.acs.org/doi/10.1021/j100002a008
• Burns, W.A.; Leopold, K.R., Unusually Large Gas−Solid Structure Differences: A Crystallographic Study of HCN−BF₃. J. Am. Chem. Soc. 1993, 115, 11622-11623. https://pubs.acs.org/doi/10.1021/ja00077a081
• Reeve, S.W.; Burns, W.A.; Lovas, F.J.; Suenram, R.D.; Leopold, K.R., Microwave Spectrum and Structure of HCN−BF₃: An Almost Weakly Bound Complex. J. Phys. Chem. 1993, 97, 10630-10637. https://pubs.acs.org/doi/10.1021/j100143a018
• Dvorak, M.A.; Ford, R.S.; Suenram, R.D.; Lovas, F.J.; Leopold, K.R., van der Waals vs. Covalent Bonding: Microwave Characterization of a Structurally Intermediate Case. J. Am. Chem. Soc. 1992, 114, 108-115. https://pubs.acs.org/doi/10.1021/ja00027a015

Electronic Structure

• Dewberry, C. T.; Huff, A. K.; Mackenzie, R. B.; Leopold, K. R., Microwave Spectrum, van der Waals Bond Length, and ¹³¹Xe Quadrupole Coupling Constant of Xe-SO₃. J. Mol. Spec., 2014, 304, 43-46. https://www.sciencedirect.com/science/article/pii/S0022285214001829
• Mackenzie, R. B.; Timp, B. A.; Mo, Y.; Leopold, K. R., Effects of a Remote Binding Partner on the Electric Field and Electric Field Gradient at an Atom in a Weakly Bound Trimer. J. Chem. Phys. 2013, 139, 034320. https://aip.scitation.org/doi/10.1063/1.4811198
• Hunt, S. W.; Shelley, D. L.; Leopold, K. R., Nuclear Hyperfine Structure in the Donor–Acceptor Complexes (CH₃)₃N–BF₃and (CH₃)₃N–B(CH₃)₃. J. Mol. Spectrosc. 2012, 281, 9–12. https://www.sciencedirect.com/science/article/pii/S0022285212001658
• Wu, S.; Sedo, G.; Leopold, K. R., Microwave Spectrum of the OD–OH₂ Complex: A Strong Deuterium Isotope Effect on Angular Momentum Quenching in the Hydroxyl Moiety. J. Mol. Spectrosc. 2009, 253, 35–40. https://www.sciencedirect.com/science/article/pii/S0022285208002701
• Brauer, C.S.; Sedo, G.; Dahlke, E.; Wu, S.; Grumstrup, E.M.; Leopold, K.R.; Marshall, M.D.; Leung, H.O.; Truhlar, D.G., Effects of ¹⁸O Isotopic Substitution on the Rotational Spectra and Potential Splitting in the OH−OH₂ Complex: Improved Measurements for ¹⁶OH−¹⁶OH₂ and ¹⁸OH−¹⁸OH₂, New Measurements for the Mixed Isotopic Forms, and ab Initio Calculations of the 2A´ − 2A´´ Energy Separation. J. Chem. Phys. 2008, 129, 104304-1-11. https://aip.scitation.org/doi/full/10.1063/1.2973638
• *Sedo, G.; Schultz, J.; Leopold, K.R., Electric Dipole Moment of Sulfuric Acid from Fourier Transform Microwave Spectroscopy. J. Mol. Spectrosc. 2008, 251, 4-8. https://www.sciencedirect.com/science/article/pii/S0022285207002603
• Ott, M.E.; Craddock, M.B.; Leopold, K.R., Nuclear Quadrupole Coupling Constants for Rare-Isotopic Forms of Nitric Acid. J. Mol. Spectrosc. 2005, 229, 286-289. https://doi.org/10.1016/j.jms.2004.10.002
• Brauer, C.S.; Sedo, G.; Grumstrup, E.M.; Leopold, K.R.; Marshall, M.D.; Leung, H.O., Effects of Partially Quenched Orbital Angular Momentum on the Microwave Spectrum and Magnetic Hyperfine Splitting in the OH-Water Complex. Chem. Phys. Lett. 2005, 401, 420-425. https://www.sciencedirect.com/science/article/pii/S0009261404018767

Other Molecules and Complexes

• Love, N.; Koziol, K.J.; Belmont, K.; Leopold, K.R., "Microwave Spectra of Two Carboxylic Acid Anhydrides: Acetic Anhydride and Acetic Difluoroacetic Anhydride", J. Mol. Spectrosc. 2024, 403, 111926.  https://doi.org/10.1016/j.jms.2024.111926
• Reynolds, A.J.; Rodriguez, D.E.; Lin, W.; Leopold, K.R., "Microwave Spectroscopy and Large Amplitude Motion of Chlorosulfonic Acid (ClSO₂OH), J. Mol. Spectrosc. 2024, 403, 111927. https://doi.org/10.1016/j.jms.2024.111927
• Love, N.; Reynolds, A.J.; Dvorak, M.A.; Leopold, K.R., "Conformational Analysis of Carboxylic Acid Anhydrides: A Microwave and Computational Study", J. Mol. Spectrosc. 2023, 397, 111844. https://doi.org/10.1016/j.jms.2023.111844
• Reynolds, A.J.; Leopold, K.R., "Microwave Spectrum and Substitution Structure of syn Thiobenzoic Acid", J. Mol. Spectrosc. 2023, 394, 111787.  https://www.sciencedirect.com/science/article/abs/pii/S0022285223000528
• *Huff, A.K.; Love, N.; Leopold, K.R., "A Microwave and Computational Study of Methanesulfonic Acid and Its Complex with Water", J. Phys. Chem. A, 2023, 127, 3658-3667.   https://pubs.acs.org/doi/10.1021/acs.jpca.3c01395
• Huff, A.K.; Love, N.; Smith, C.J.; Leopold, K.R., Parent, ³⁴S, and Deuterated Triflic Acid: Microwave Spectra and Splittings Due to Hydroxyl Torsion, J. Mol. Spectrosc. 2022, 385, 111623. https://www.sciencedirect.com/science/article/pii/S0022285222000455
• Huff, A.K.; Ward, Rebecca M.; Leopold, K.R. Microwave Spectrum and Structure of the SO₃-SO₂ Weakly Bound Complex, J. Mol. Spectrosc. 2020, 371, 111327. https://www.sciencedirect.com/science/article/pii/S0022285220300953
• Love, N.; Smith, C.J.; Huff, A.K.; Leopold, K.R., Microwave and Computational Study of Trifluoroacetic Anhydride, J. Mol. Spectrosc. 2019, 365, 111210. https://www.sciencedirect.com/science/article/pii/S0022285219302127
• Smith, C.J.; Huff, A.K.;Zhang, H.; Mo, Y.; Leopold, K.R., A Strong Dependence of the CH₃ Internal Rotation Barrier on Conformation in Thioacetic Acid: Microwave Measurements and an Energy Decomposition Analysis, J. Chem. Phys. 2019, 150, 134202. https://aip.scitation.org/doi/10.1063/1.5087718
• Huff, A.K.; Smith, C.J.; Leopold, K.R., Microwave Spectrum and Structure of the Lowest A-Internal Rotor State of Ar···CH₃I, J. Mol. Spectrosc. 2018, 353, 6-10. https://www.sciencedirect.com/science/article/pii/S0022285218302261
• Mackenzie, R.B; Dewberry, C.T.; Cornelius, R.D.; Smith, C.J.; Leopold, K.R., Multidimensional Large Amplitude Dynamics in the Pyridine-Water Complex, J. Phys. Chem. A 2017, 121, 855-860. https://pubs.acs.org/doi/10.1021/acs.jpca.6b11255
• Dewberry, C.T.; Mueller, J.L.; Mackenzie, R.B.; Timp, B.A.; Marshall, M.D.; Leung, H.O.; Leopold, K.R., The Effect of Ortho-Fluorination on Intermolecular Interactions of Pyridine: Microwave Spectrum and Structure of the CO₂−2,6-Difluoropyridine Weakly Bound Complex, J. Mol. Struct. 2017, 1146, 373-379. 379. https://www.sciencedirect.com/science/article/pii/S0022286017307913
• Dewberry, C.T.; Cornelius, R.D.; Mackenzie, R.B.; Smith, C.J.; Dvorak, M.A.; Leopold, K.R., Microwave Spectrum and Structure of the 3,5-Difluoropyridine···CO₂ van der Waals Dimer, J. Mol. Spectrosc. 2016, 328, 67-7272. https://www.sciencedirect.com/science/article/pii/S0022285216301825
• Mackenzie, R.B.; Dewberry, C.T.; Coulston, E.; Cole, G.C.; Legon, A.C., Tew, D.P.; Leopold, K.R., Intramolecular Competition between n-Pair and pi-Pair Hydrogen Bonding: Microwave Spectrum and Internal Dynamics of the Pyridine-Acetylene Hydrogen-Bonded Complex, J. Chem. Phys. 2015, 143, 104309. https://aip.scitation.org/doi/10.1063/1.4929997
• Timp, B. A.; Doran, J. L.; Iyer, S.; Grabow, J.U.; Leopold, K.R. Microwave Observation of ⁴¹K⁷⁹Br and ⁴¹K⁸¹Br from Laser-Ablated Potassium Bromide. J. Mol. Spectrosc. 2012, 271, 20–24. https://www.sciencedirect.com/science/article/pii/S0022285211002797
• Doran, J. L.; Hon, B.; Leopold, K.R., Rotational Spectrum and Structure of the Pyridine–CO₂ van der Waals Complex. J. Mol. Spectrosc. 2012, 1019, 191–195.
• Wu, S.; Sedo, G.; Grumstrup, E. M.; Leopold, K.R., Microwave Spectra of O₂–HF and O₂–DF: Hyperfine Interactions and Global Fitting with Infrared Data. J. Chem. Phys. 2007, 127, 204315–1-11. https://aip.scitation.org/doi/10.1063/1.2804770
• Fiacco, D.L.; Kirchner, B.; Burns, W.A.; Leopold, K.R., Quadrupole Coupling Constants for ³³SO₃: Microwave Measurements for Ar-³³SO₃ and ab initio Results for the ³³SO₃ Monomer. J. Mol. Spectrosc. 1998, 191, 389-391. https://pubmed.ncbi.nlm.nih.gov/9753578/