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Lichter KE, Bloom JR, Sheu RD, Zalavari LT, Leung K, Collins A, Witztum A, Chuter R. Tracking and Reducing SF 6 Usage in Radiation Oncology: A Step Toward Net-Zero Health Care Emissions. Pract Radiat Oncol 2023; 13:e471-e474. [PMID: 37414248 DOI: 10.1016/j.prro.2023.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/21/2023] [Accepted: 06/22/2023] [Indexed: 07/08/2023]
Abstract
Sulfur hexafluoride (SF6) is a widely used insulating gas in medical linear accelerators (LINACs) due to its high dielectric strength, heat transfer capabilities, and chemical stability. However, its long lifespan and high Global Warming Potential (GWP) make it a significant contributor to the environmental impact of radiation oncology. SF6 has an atmospheric lifespan of 3200 years and a GWP 23,000 times that of carbon dioxide. The amount of SF6 that can be emitted through leakage from machines is also concerning. It is estimated that the approximate 15,042 LINACs globally may leak up to 64,884,185.9 carbon dioxide equivalent per year, which is the equivalent greenhouse gas emissions of 13,981 gasoline-powered passenger vehicles driven for 1 year. Despite being regulated as a greenhouse gas under the United Nations Framework Convention on Climate Change, SF6 use within health care is often exempt from regulation, and only a few states in the United States have specific SF6 management regulations. This article highlights the need for radiation oncology centers and LINAC manufacturers to take responsibility for minimizing SF6 emissions. Programs that track usage and disposal, conduct life-cycle assessments, and implement leakage detection can help identify SF6 sources and promote recovery and recycling. Manufacturers are investing in research and development to identify alternative gases, improve leak detection, and minimize SF6 gas leakage during operation and maintenance. Alternative gases with lower GWP, such as nitrogen, compressed air, and perfluoropropane, may be considered as replacements for SF6; however, more research is needed to evaluate their feasibility and performance in radiation oncology. The article emphasizes the need for all sectors, including health care, to reduce their emissions to meet the goals of the Paris Agreement and ensure the sustainability of health care and our patients. Although SF6 is practical in radiation oncology, its environmental impact and contribution to the climate crisis cannot be ignored. Radiation oncology centers and manufacturers must take responsibility for reducing SF6 emissions by implementing best practices and promoting research and development around alternatives. To meet global emissions reduction goals and protect both planetary and patient health, the reduction of SF6 emissions will be essential.
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Affiliation(s)
- Katie E Lichter
- Department of Radiation Oncology, University of California, San Francisco, California.
| | - Julie R Bloom
- Department of Radiation Oncology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Ren-Dih Sheu
- Department of Radiation Oncology, Icahn School of Medicine at Mount Sinai, New York, New York
| | | | - Kayla Leung
- University of California, Berkeley, California
| | - Amy Collins
- Health Care Without Harm, Reston, Virginia; Department of Emergency Medicine, MetroWest Medical Center, Framingham, Massachusetts
| | - Alon Witztum
- Department of Radiation Oncology, University of California, San Francisco, California
| | - Robert Chuter
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, United Kingdom; Division of Cancer Sciences, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
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Caviezel M, Horká-Zelenková V, Seyfang G, Quack M. High resolution FTIR and diode laser spectroscopy of trifluoromethylacetylene and tetrafluoromethane in a supersonic jet expansion. Mol Phys 2022. [DOI: 10.1080/00268976.2022.2093285] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Affiliation(s)
- M. Caviezel
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | | | - G. Seyfang
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
| | - M. Quack
- Laboratorium für Physikalische Chemie, ETH Zürich, Zürich, Switzerland
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Concina B, Montagne G, Martin S, Bordas C. Kinetic energy released in the vibrational autodetachment of sulfur hexafluoride anion. J Chem Phys 2021; 154:234306. [PMID: 34241271 DOI: 10.1063/5.0054199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The kinetic energy release distribution (KERD) in the vibrational autodetachment (VAD) from sulfur hexafluoride anion SF6 - has been measured in a velocity map imaging spectrometer for delays in the range of a few tens of microseconds. The experimental KERD is analyzed within the framework of the detailed-balance: first using the standard Langevin model and subsequently using a more refined and realistic model based on the experimental attachment cross section. A discussion on the processes involved in the attachment and the VAD is presented based on an empirical fit of the attachment cross section. The lifetime derived from the model is in good agreement with the experimental time window, strengthening this theoretical approach for this model system.
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Affiliation(s)
- Bruno Concina
- Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, CNRS, F-69622 Villeurbanne, France
| | - Guillaume Montagne
- Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, CNRS, F-69622 Villeurbanne, France
| | - Serge Martin
- Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, CNRS, F-69622 Villeurbanne, France
| | - Christian Bordas
- Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, CNRS, F-69622 Villeurbanne, France
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Taylor WS, Redmon XS, Scheuter BA. State-Specific Reactions of Cu(+)((1)S,(3)D) with SF6 and SF5Cl. J Phys Chem A 2016; 120:2295-306. [PMID: 27014999 DOI: 10.1021/acs.jpca.6b01534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
State-specific reactions of Cu(+)((1)S,(3)D) were carried out in a selected ion drift cell apparatus with SF6 and SF5Cl. Copper ions were prepared in a glow discharge utilizing Ne as the working gas. Analysis of Cu(+) states using ion mobility mass spectrometry (IMS) indicated the presence of both Cu(+)(3d(10)) and Cu(+)(3d(9)4s(1)) configurations attributable to the (1)S ground and (3)D first excited states of this metal ion, respectively. State-specific product formation in reactions of these ions with the two neutral substrates of interest here was determined using IMS along with both known and calculated energetic requirements for product formation. These experiments indicate that Cu(+)((1)S) associates with both SF6 and SF5Cl; however, the process is approximately four times as efficient with the latter neutral under these conditions. Association is also observed as a minor product between Cu(+)((3)D) and both neutral reactants. Inefficient formation of SF3(+) occurs as the sole bimolecular product from SF6 via Cu(+)((3)D). In contrast, Cu(+)((3)D) reacts with SF5Cl in rapid parallel bimolecular processes yielding SF3(+) and CuCl(+). These results also indicate that CuCl(+) initiates additional higher-order processes which result in SF5(+) and SF4Cl(+). The energetics associated with the formation of SF3(+) suggest that a copper halide neutral byproduct must also be formed, requiring a more complex mechanism than simple dissociative charge-transfer.
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Affiliation(s)
- William S Taylor
- Department of Chemistry, University of Central Arkansas , Conway, Arkansas 72035, United States
| | - Xavier S Redmon
- Department of Chemistry, University of Central Arkansas , Conway, Arkansas 72035, United States
| | - Benjamin A Scheuter
- Department of Chemistry, University of Central Arkansas , Conway, Arkansas 72035, United States
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Akhgarnusch A, Höckendorf RF, Beyer MK. Thermochemistry of the Reaction of SF6 with Gas-Phase Hydrated Electrons: A Benchmark for Nanocalorimetry. J Phys Chem A 2015; 119:9978-85. [PMID: 26356833 DOI: 10.1021/acs.jpca.5b06975] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction of sulfur hexafluoride with gas-phase hydrated electrons (H2O)n(-), n ≈ 60-130, is investigated at temperatures T = 140-300 K by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. SF6 reacts with a temperature-independent rate of 3.0 ± 1.0 × 10(-10) cm(3) s(-1) via exclusive formation of the hydrated F(-) anion and the SF5(•) radical, which evaporates from the cluster. Nanocalorimetry yields a reaction enthalpy of ΔHR,298K = 234 ± 24 kJ mol(-1). Combined with literature thermochemical data from bulk aqueous solution, these result in an F5S-F bond dissociation enthalpy of ΔH298K = 455 ± 24 kJ mol(-1), in excellent agreement with all high-level quantum chemical calculations in the literature. A combination with gas-phase literature thermochemistry also yields an experimental value for the electron affinity of SF5(•), EA(SF5(•)) = 4.27 ± 0.25 eV.
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Affiliation(s)
- Amou Akhgarnusch
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel , Olshausenstrasse 40, 24098 Kiel, Germany.,Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens-Universität Innsbruck , Technikerstrasse 25, 6020 Innsbruck, Austria
| | - Robert F Höckendorf
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel , Olshausenstrasse 40, 24098 Kiel, Germany
| | - Martin K Beyer
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel , Olshausenstrasse 40, 24098 Kiel, Germany.,Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens-Universität Innsbruck , Technikerstrasse 25, 6020 Innsbruck, Austria
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Luzon I, Nagler M, Heber O, Strasser D. SF6(-) photodetachment near the adiabatic limit. Phys Chem Chem Phys 2015; 17:7670-5. [PMID: 25606820 DOI: 10.1039/c4cp05068a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High sensitivity photodetachment cross-section measurements of SF6(-) are performed near the adiabatic threshold limit. The extraction of adiabatic detachment energy (ADE) from the high sensitivity measurement of the cross-section change as a function of photon energy is discussed. Below the vertical detachment energy a steep 4 orders of magnitude cross-section drop is observed, with cross sections as low as 2 × 10(-6) Å(2) measured for photon energies below 2 eV. The cross-section is fitted with both the expected spectral shape based on recently calculated Frank-Condon overlaps and a phenomenological threshold function. The resulting 1.7 ± 0.02 eV ADE values are significantly higher than previously recommended experimental ADE values obtained based on kinetics modeling, and possible differences between the experimental approaches are discussed.
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Affiliation(s)
- I Luzon
- Institute of Chemistry, The Hebrew university of Jerusalem, Jerusalem, 91904, Israel.
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Boudon V, Mitchell J, Domanskaya A, Maul C, Georges R, Benidar A, Harter W. High-resolution spectroscopy and analysis of the ν3/2ν4dyad of CF4. Mol Phys 2011. [DOI: 10.1080/00268976.2011.621900] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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8
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Eisfeld W. Highly accurate determination of the electron affinity of SF 6 and analysis of structure and photodetachment spectrum of SF 6−. J Chem Phys 2011; 134:054303. [DOI: 10.1063/1.3544213] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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10
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Schneider H, Takahashi K, Skodje RT, Weber JM. Infrared spectra of SF6(-) x HCOOH x Ar(n) (n = 0-2): infrared triggered reaction and Ar-induced reactive inhibition. J Chem Phys 2009; 130:174302. [PMID: 19425771 DOI: 10.1063/1.3125960] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present the infrared spectra of SF(6)(-) x HCOOH x Ar(m) (m=0-2) complexes. We find that the binding motif involves a single hydrogen bond between the SF(6)(-) anion and the OH group of the formic acid, with the CH group weakly tethered to a neighboring F atom. Similar to the case of hydrated SF(6)(-), the SF bond involved in the (OH-F) bond is significantly stretched and weakened by the attachment of the HCOOH ligand. The bare complex undergoes reaction upon infrared absorption in the CH/OH stretching region of the formic acid moiety, leading predominantly to the formation of SF(4)(-) + 2HF + CO(2). The reaction can be inhibited by attachment of two Ar atoms. We discuss a likely reaction mechanism in the framework of ab initio calculations, suggesting that reaction proceeds via tunneling through the potential barrier.
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Affiliation(s)
- Holger Schneider
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, Colorado 80309, USA
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11
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Mühle J, Huang J, Weiss RF, Prinn RG, Miller BR, Salameh PK, Harth CM, Fraser PJ, Porter LW, Greally BR, O'Doherty S, Simmonds PG. Sulfuryl fluoride in the global atmosphere. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jd011162] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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12
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Tsai WT. Environmental hazards and health risk of common liquid perfluoro-n-alkanes, potent greenhouse gases. ENVIRONMENT INTERNATIONAL 2009; 35:418-424. [PMID: 18845341 DOI: 10.1016/j.envint.2008.08.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 08/14/2008] [Accepted: 08/16/2008] [Indexed: 05/26/2023]
Abstract
This article aimed at introducing the main physical properties and commercial/industrial uses of common liquid perfluoro-n-alkanes (including perfluoropentane, perfluorohexane, perfluoroheptane, perfluorooctane, and perfluorononane) and the environment and health hazards posed by their toxic decomposition products (especially in hydrogen fluoride and perfluoroisobutylene) because these perfluorocompounds are potent greenhouse gases, which have been blanketed into the Kyoto Protocol, but was rarely described in the National Inventory Reports by Annex I Parties. The environmental properties (including octanol-water partition coefficient, water solubility and Henry's law constant) of liquid perfluoro-n-alkanes were evaluated, and further discussed were its atmospheric implications according to the predicted properties and possible proposal for the formation of trifluoroacetic acid (CF(3)COOH) in the atmosphere by the ionized photolysis. These predicted values revealed that liquid perfluoro-n-alkanes tend to be hydrophobic and partitioned into organic matter, and they have exceptionally low solubility in water and extremely high vaporization from the water bodies, suggesting that it will sink into the atmosphere if it is released into the environment.
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Affiliation(s)
- Wen-Tien Tsai
- Graduate Institute of Bioresources, National Pingtung University of Science and Technology, Pingtung 912, Taiwan.
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13
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Steill JD, Oomens J, Eyler JR, Compton RN. Gas-phase infrared multiple photon dissociation spectroscopy of isolated SF6− and SF5− anions. J Chem Phys 2008; 129:244302. [DOI: 10.1063/1.3036977] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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14
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Bruska MK, Piechota J. Density functional study of sulphur hexafluoride (SF6) and its hydrogen derivatives. MOLECULAR SIMULATION 2008. [DOI: 10.1080/08927020802258708] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
| | - Jacek Piechota
- b Interdisciplinary Centre for Materials Modelling, University of Warsaw , Warsaw, Poland
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16
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Nassar R, Bernath PF, Boone CD, McLeod SD, Skelton R, Walker KA, Rinsland CP, Duchatelet P. A global inventory of stratospheric fluorine in 2004 based on Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) measurements. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006jd007395] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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ElSohly AM, Renault ML, Tschumper GS. Reliable Electron Affinities of Perfluorocyclopropane and Perfluorocyclobutane from Convergent ab Initio Computations. J Phys Chem A 2006; 110:1975-7. [PMID: 16451032 DOI: 10.1021/jp0557722] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
To resolve discrepancies concerning the magnitude of the electron affinities of perfluorocyclopropane and perfluorocyclobutane, quantum chemical calculations have been carried out with the MP2 and CCSD(T) methods in conjunction with augmented correlation consistent basis sets (aug-cc-pVX Z, X = D, T, Q). Though no experimental values have been found for perfluorocyclopropane, we estimate its electron affinity to be 0.17 eV (0.00 eV without zero-point vibrational energy corrections). In addition, determination of the electron affinity of perfluorocyclobutane (0.61 and 0.44 eV with and without zero-point vibrational energy corrections, respectively) is in good agreement with experimental values reported by Miller and co-workers (0.63 +/- 0.05 eV). This study also demonstrates that the widely prescribed B3LYP/DZP++ model chemistry for computing electron affinities does not correctly describe these systems.
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Affiliation(s)
- Adel M ElSohly
- Department of Chemistry and Biochemistry, University of Mississippi, University, Mississippi 38677-1848, USA
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19
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Hurst DF, Lin JC, Romashkin PA, Daube BC, Gerbig C, Matross DM, Wofsy SC, Hall BD, Elkins JW. Continuing global significance of emissions of Montreal Protocol–restricted halocarbons in the United States and Canada. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005jd006785] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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20
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Paul A, Wannere CS, Kasalova V, Schleyer PVR, Schaefer HF. The Peculiar Trend of Cyclic Perfluoroalkane Electron Affinities with Increasing Ring Size. J Am Chem Soc 2005; 127:15457-69. [PMID: 16262410 DOI: 10.1021/ja053310w] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The adiabatic electron affinities (AEAs), vertical electron affinities (VEAs), and vertical detachment energies (VDEs) of cyclic perfluoroalkanes, c-C(n)F(2n) (n = 3-7), and their monotrifluoromethyl derivatives were computed using various pure and hybrid density functionals with DZP++ (polarization and diffuse function augmented double-zeta) basis sets. The theoretical AEA of c-C(4)F(8) at KMLYP/DZP++ is 0.70 eV, which exhibits satisfactory agreement with the 0.63 +/- 0.05 eV experimental value. The nonzero-point-corrected AEA of c-C(4)F(8) is predicted to be 0.41 eV at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ level of theory, which shows a slight deviation of 0.11 eV from the KMLYP estimated value of 0.52 eV for the same. With the zero-point correction from the MP2/6-311G(d) [Gallup, G. A. Chem. Phys. Lett. 2004, 399, 206] level of theory combined with the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ result, the most reliable estimate of AEA of c-C(4)F(8) is 0.60 eV. c-C(3)F(6)(-), c-C(4)F(8)(-), and c-C(5)F(10)(-) are unusual in preferring planar to near planar ring structures. The ZPE-corrected AEAs of c-C(n)F(2n) increase from n = 3 (0.24 eV) to n = 5 (0.77 eV), but then dramatically fall off to 0.40 eV for both n = 6 and n = 7. All of the other functionals predict the same trend. This is due to a change in the structural preference: C(s)() c-C(6)F(12)(-) and C(1) c-C(7)F(14)(-) are predicted to favor nonplanar rings, each with an exceptionally long C-F bond. (There also is a second, higher energy D3d minimum for C(6)F(12)(-).) The SOMOs as well as the spin density plots of the c-PFA radical anions reveal that the "extra" electron is largely localized on the unique F atoms in the larger n = 6 and n = 7 rings but is delocalized in the multiatom SOMOs of the three- to five-membered ring radical anions. The computed AEAs are much larger than the corresponding VEAs; the latter are not consistent with different functionals. The AEAs are substantially larger when a c-C(n)()F(2)(n)() fluorine is replaced by a -CF(3) group. This behavior is general; PFAs with tertiary C-F bonds have large AEAs. The VDEs for all the anions are substantial, ranging from 1.89 to 3.64 eV at the KMLYP/DZP++ level.
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Affiliation(s)
- Ankan Paul
- Center for Computational Chemistry, Department of Chemistry, University of Georgia, Athens, GA 30602-2525, USA
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ElSohly AM, Tschumper GS, Crocombe RA, Wang JT, Williams F. Computational and ESR Studies of Electron Attachment to Decafluorocyclopentane, Octafluorocyclobutane, and Hexafluorocyclopropane: Electron Affinities of the Molecules and the Structures of Their Stable Negative Ions as Determined from 13C and 19F Hyperfine Coupling Constants. J Am Chem Soc 2005; 127:10573-83. [PMID: 16045345 DOI: 10.1021/ja0505898] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-resolution ESR spectra of the ground-state negative ions of hexafluorocyclopropane (c-C3F6*-), octafluorocyclobutane (c-C4F8*-), and decafluorocyclopentane (c-C5F10*-) are reported and their isotropic 19F hyperfine coupling constants (hfcc) of 198.6 +/- 0.4 G, 147.6 +/- 0.4 G, and 117.9 +/- 0.4 G, respectively, are in inverse ratio to the total number of fluorine atoms per anion. Together with the small value of 5.2 +/- 0.4 G determined for the isotropic 13C hfcc of c-C4F8*-, these results indicate that in each case the singly occupied molecular orbital (SOMO) is delocalized over the equivalent fluorines and possesses a nodal plane through the carbon atoms of a time-averaged D(nh) structure. A series of quantum chemical computations were carried out to further characterize these anions and their neutral counterparts. Both the B3LYP density functional and second-order Møller-Plesset perturbation theory (MP2) indicate that c-C3F6*- adopts a D(3h) geometry and a (2)A2'' ground electronic state, that c-C4F8*- adopts a D(4h) geometry and a (2)A2u ground electronic state, and that c-C5F10*- adopts a C(s) structure and a (2)A' electronic state. Moreover, the 19F hyperfine coupling constants computed with the MP2 method and a high quality triple-zeta basis set are within 1% of the experimental values. Also, the values computed for the 13C hfcc of c-C4F8*- are consistent with the experimental value of 5.2 G. Therefore, in keeping with the ESR results, these negative ions derived from first-row elements can be characterized as pi* species. In addition, the hypervalency of these perfluorocycloalkane radical anions has been clarified.
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Affiliation(s)
- Adel M ElSohly
- Department of Chemistry and Biochemistry, The University of Mississippi, University, Mississippi 38677, USA
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Jelisavcic M, Panajotovic R, Kitajima M, Hoshino M, Tanaka H, Buckman SJ. Electron scattering from perfluorocyclobutane (c-C4F8). J Chem Phys 2004; 121:5272-80. [PMID: 15352820 DOI: 10.1063/1.1782174] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report experimental results for electron scattering from perfluorocyclobutane, c-C(4)F(8), obtained from measurements in our two laboratories. A set of differential, integral, and momentum transfer cross sections is provided for elastic scattering for incident electron energies from 1.5 to 100 eV. Inelastic scattering (vibrational excitation) cross sections have been measured for incident electron energies of 1.5, 2, 5, 6, and 7 eV. In order to investigate the role of intermediate negative ions (resonances) in the scattering process we have also measured an excitation function for elastic scattering and vibrational excitation of the ground electronic state of C(4)F(8) for incident energies between 0.6 and 20 eV. These results are compared with the limited amount of data available in the literature for scattering from this molecule.
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Affiliation(s)
- M Jelisavcic
- Atomic and Molecular Physics Laboratories, Research School of Physical Sciences & Engineering, Australian National University, Canberra Australian Capital Territory, Australia
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Miller TM, Friedman JF, Viggiano AA. Electron attachment and detachment and the electron affinity of cyclo-C4F8. J Chem Phys 2004; 120:7024-8. [PMID: 15267603 DOI: 10.1063/1.1683082] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
New measurements have been made of rate constants for electron attachment to c-C(4)F(8) (octafluorocyclobutane) and thermal electron detachment from the parent anion, c-C(4)F(8) (-), over the temperature range 298-400 K in 133 Pa of He gas in a flowing-afterglow Langmuir-probe apparatus. From these data the electron affinity for c-C(4)F(8) was determined, EA(c-C(4)F(8))=0.63+/-0.05 eV. The motivation was to resolve a discrepancy between our earlier EA estimate and a higher value (EA=1.05+/-0.10 eV) reported from a recent experiment of Hiraoka et al. [J. Chem. Phys. 116, 7574 (2002)]. The electron attachment rate constant is 9.3+/-3.0x10(-9) cm(3) s(-1) at 298 K. The electron detachment rate constant is negligible at room temperature but climbs to 1945+/-680 s(-1) at 400 K. G3(MP2) calculations were carried out for the neutral (D(2d), (1)A(1)) and anion (D(4h), (2)A(2u)) and yielded EA(c-C(4)F(8) (-))=0.595 eV. Bond energies were also calculated for loss of F from c-C(4)F(8) and loss of F or F(-) from c-C(4)F(8) (-). From these, dissociative electron attachment is found to be endothermic by at least 1.55 eV.
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Affiliation(s)
- Thomas M Miller
- Air Force Research Laboratory, Space Vehicles Directorate, Hanscom Air Force Base, Bedford, Massachusetts 01731-3010, USA.
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Chim R, Kennedy R, Tuckett R. The vacuum-UV absorption spectrum of SF5CF3; implications for its lifetime in the earth’s atmosphere. Chem Phys Lett 2003. [DOI: 10.1016/s0009-2614(02)01763-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Yamamoto M, Yamashita K, Sadakata M. Study of the Reactions of O-with CF4and CHF3by Ab Initio Calculations. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2002. [DOI: 10.1246/bcsj.75.1483] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Miller TM, Arnold ST, Viggiano AA, Knighton WB. Electron attachment to SF5CF3 (296–563 K) and calculations of the neutral and anion thermochemistry. J Chem Phys 2002. [DOI: 10.1063/1.1457442] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Reddmann T, Ruhnke R, Kouker W. Three-dimensional model simulations of SF6with mesospheric chemistry. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000jd900700] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Houweling S, Dentener F, Lelieveld J, Walter B, Dlugokencky E. The modeling of tropospheric methane: How well can point measurements be reproduced by a global model? ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999jd901149] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Thomas R, Liu Y, Mayhew C, Peverall R. Selected ion flow tube studies of the gas-phase reactions of O·−, O2·− and OH− with a variety of brominated compounds. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s0168-1176(96)04409-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Jarvis GK, Mayhew CA, Tuckett RP. Study of the Gas Phase Reactions of Several Perfluorocarbons with Positive Ions of Atmospheric Interest. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960071d] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gary K. Jarvis
- Chemical Physics Laboratory, School of Physics and Space Research, and School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K
| | - Chris A. Mayhew
- Chemical Physics Laboratory, School of Physics and Space Research, and School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K
| | - Richard P. Tuckett
- Chemical Physics Laboratory, School of Physics and Space Research, and School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, U.K
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Molina MJ, Molina LT, Kolb CE. GAS-PHASE AND HETEROGENEOUS CHEMICAL KINETICS OF THE TROPOSPHERE AND STRATOSPHERE. Annu Rev Phys Chem 1996. [DOI: 10.1146/annurev.physchem.47.1.327] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mario J. Molina
- Department of Earth, Atmospheric and Planetary Sciences and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Luisa T. Molina
- Department of Earth, Atmospheric and Planetary Sciences and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Charles E. Kolb
- Center for Chemical and Environmental Physics, Aerodyne Research, Inc, Billerica, Massachusetts 01821-3976
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Lasa J, Rosiek J, Drozdowicz B. Analysis of the possibility of SF6 detection by a solute switching method with a modulator containing a 63Ni source. J Chromatogr A 1996. [DOI: 10.1016/0021-9673(96)00292-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Levin I, Hesshaimer V. Refining of atmospheric transport model entries by the globally observed passive tracer distributions of85krypton and sulfur hexafluoride (SF6). ACTA ACUST UNITED AC 1996. [DOI: 10.1029/96jd01058] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Morris RA, Viggiano AA, Paulson JF. Reactivity of gas-phase anions with fully halogenated alkanes. INT REV PHYS CHEM 1996. [DOI: 10.1080/01442359609353180] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Morris RA, Viggiano A, Arnold ST, Paulson JF. Chemistry of atmospheric ions reacting with fully fluorinated compounds. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0168-1176(95)04258-m] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Culbertson J, Grimsrud E. Fates of the molecular anions of SF6 and C7F14 upon recombination with positive ions. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/0168-1176(95)04244-f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Stevens Miller AE, Miller TM, Viggiano AA, Morris RA, Van Doren JM, Arnold ST, Paulson JF. Negative ion chemistry of SF4. J Chem Phys 1995. [DOI: 10.1063/1.468940] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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