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Matthaei CT, Mukhopadhyay DP, Röder A, Poisson L, Fischer I. Photodissociation of the trichloromethyl radical: photofragment imaging and femtosecond photoelectron spectroscopy. Phys Chem Chem Phys 2022; 24:928-940. [PMID: 34913455 DOI: 10.1039/d1cp04084g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Halogen-containing radicals play a key role in catalytic reactions leading to stratospheric ozone destruction, thus their photochemistry is of considerable interest. Here we investigate the photodissociation dynamics of the trichloromethyl radical, CCl3 after excitation in the ultraviolet. While the primary processes directly after light absorption are followed by femtosecond-time resolved photoionisation and photoelectron spectroscopy, the reaction products are monitored by photofragment imaging using nanosecond-lasers. The dominant reaction is loss of a Cl atom, associated with a CCl2 fragment. However, the detection of Cl atoms is of limited value, because in the pyrolysis CCl2 is formed as a side product, which in turn dissociates to CCl + Cl. We therefore additionally monitored the molecular fragments CCl2 and CCl by photoionisation at 118.2 nm and disentangled the contributions from various processes. A comparison of the CCl images with control experiments on CCl2 suggest that the dissociation to CCl + Cl2 contributes to the photochemistry of CCl3.
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Affiliation(s)
- Christian T Matthaei
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
| | - Deb Pratim Mukhopadhyay
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
| | - Anja Röder
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany. .,LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France.
| | - Lionel Poisson
- LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France. .,Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d*Orsay, 91405, Orsay, France
| | - Ingo Fischer
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
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2
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Datta S, Davis HF. Site-Specific Carbon-Carbon Bond Fission in Photoexcited Propyl Radicals Leads to Isomer-Selective Carbene and Radical Products. J Phys Chem Lett 2021; 12:11926-11930. [PMID: 34878789 DOI: 10.1021/acs.jpclett.1c03324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Although there have been many studies of C-H bond fission in the UV photochemistry of alkyl radicals, very little is known about the possible occurrence of C-C bond fission. Here, we report that upon excitation at 248 nm, gaseous 1-propyl radicals primarily undergo C-C bond fission, producing methylene (CH2) and ethyl radicals (C2H5), rather than the more energetically favored methyl (CH3) and ethylene (C2H4). In contrast, the exclusive C-C bond fission products from 2-propyl radicals were ethylidene (CHCH3) plus methyl radicals (CH3). The isomer-selective formation of high-energy carbene + radical products involves excited-state site-specific C-C bond fission at the radical carbon, with quantum yields comparable to those for C-H bond fission. Our observations suggest that a general feature of alkyl radical photochemistry is predissociation of the initially formed Rydberg states by high-lying valence states, yielding high-energy carbene plus alkyl radical products.
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Affiliation(s)
- Sagnik Datta
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, United States
| | - H Floyd Davis
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, United States
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3
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Marggi Poullain S, Rubio-Lago L, Chicharro DV, Boullagui A, Zanchet A, Yazidi O, García-Vela A, Bañares L. Imaging the elusive C–C bond dissociation channel of photoexcited ethyl radical. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1984598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Sonia Marggi Poullain
- Facultad de Ciencias Químicas, Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Universidad Complutense de Madrid, Madrid, Spain
| | - Luis Rubio-Lago
- Facultad de Ciencias Químicas, Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Universidad Complutense de Madrid, Madrid, Spain
| | - David V. Chicharro
- Facultad de Ciencias Químicas, Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Universidad Complutense de Madrid, Madrid, Spain
| | - Aymen Boullagui
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA LR01ES09, Faculté des Sciences de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Alexandre Zanchet
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Ounaies Yazidi
- Laboratoire de Spectroscopie Atomique, Moléculaire et Applications-LSAMA LR01ES09, Faculté des Sciences de Tunis, Université de Tunis El Manar, Tunis, Tunisia
| | - Alberto García-Vela
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Luis Bañares
- Facultad de Ciencias Químicas, Departamento de Química Física (Unidad Asociada I+D+i al CSIC), Universidad Complutense de Madrid, Madrid, Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience), Madrid, Spain
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4
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Lucas M, Sun G, Liu Y, Shao K, Zhang J. Ultraviolet Photodissociation Dynamics of the Cyclohexyl Radical: The H-Atom Product Channel. J Phys Chem A 2021; 125:5534-5543. [PMID: 34133143 DOI: 10.1021/acs.jpca.1c03526] [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
The ultraviolet (UV) photodissociation dynamics of the jet-cooled cyclohexyl (c-C6H11) radical is studied using the high-n Rydberg atom time-of-flight (HRTOF) technique. The cyclohexyl radical is produced by the 193 nm photodissociation of chlorocyclohexane and bromocyclohexane and is examined in the photolysis wavelength region of 232-262 nm. The H-atom photofragment yield (PFY) spectrum contains a broad peak centered at 250 nm, which is in good agreement with the UV absorption spectrum of the cyclohexyl radical and assigned to the 3p Rydberg states. The translational energy distributions of the H-atom loss product channel, P(ET)'s, are bimodal, with a slow (low ET) component peaking at ∼6 to 7 kcal/mol and a fast (high ET) component peaking at ∼44-48 kcal/mol. The fraction of the average translational energy in the total excess energy, ⟨fT⟩, is in the range of 0.16-0.25 in the photolysis wavelength region of 232-262 nm. The H-atom product angular distribution of the slow component is isotropic, while that of the fast component is anisotropic with an anisotropy parameter of β ≈ 0.5-0.7. The bimodal product translational energy and angular distributions indicate two dissociation pathways to the H + C6H10 products in cyclohexyl. The high-ET anisotropic component is from a repulsive, prompt dissociation on a repulsive potential energy surface coupling with the Rydberg excited states to produce H + cyclohexene. The low-ET isotropic component is consistent with the unimolecular dissociation of hot radical on the ground electronic state after internal conversion from the Rydberg states. The similarity of the photodissociation dynamics of the cyclohexyl radical to the previously studied small linear and branched alkyls expands on the understanding of the dissociation dynamics of alkyl radicals to include larger cyclic alkyl radicals.
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Affiliation(s)
- Michael Lucas
- Department of Chemistry University of California at Riverside, Riverside, California 92521 United States
| | - Ge Sun
- Department of Chemistry University of California at Riverside, Riverside, California 92521 United States
| | - Yanlin Liu
- Department of Chemistry University of California at Riverside, Riverside, California 92521 United States
| | - Kuanliang Shao
- Department of Chemistry University of California at Riverside, Riverside, California 92521 United States
| | - Jingsong Zhang
- Department of Chemistry University of California at Riverside, Riverside, California 92521 United States
- Air Pollution Research Center, University of California, Riverside, California 92521 United States
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5
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Ramphal IA, Shapero M, Neumark DM. Photodissociation Dynamics of the Cyclohexyl Radical from the 3p Rydberg State at 248 nm. J Phys Chem A 2021; 125:3900-3911. [PMID: 33913714 DOI: 10.1021/acs.jpca.1c02393] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The photodissociation of jet-cooled cyclohexyl was studied by exciting the radicals to their 3p Rydberg state by using 248 nm laser light and detecting photoproducts by photofragment translational spectroscopy. Both H atom loss and dissociation to heavy fragment pairs are observed. The H atom loss channel exhibits a two-component translational energy distribution. The fast photoproduct component is attributed to impulsive cleavage directly from an excited state, likely the Rydberg 3s state, forming cyclohexene. The slow component is due to statistical decomposition of hot cyclohexyl radicals that internally convert to the ground electronic state prior to H atom loss. The fast and slow components are present in an ∼0.7:1 ratio, similar to findings in other alkyl radicals. Internal conversion to the ground state also leads to ring-opening followed by dissociation to 1-buten-4-yl + ethene in comparable yield to H-loss, with the C4H7 fragment containing enough internal energy to dissociate further to butadiene via H atom loss. A very minor ground-state C5H8 + CH3 channel is observed, attributed predominantly to 1,3-pentadiene formation. The ground-state branching ratios agree well with RRKM calculations, which also predict C4H6 + C2H5 and C3H6 + C3H5 channels with similar yield to C5H8 + CH3. If these channels were active, it was at levels too low to be observed.
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Affiliation(s)
- Isaac A Ramphal
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Mark Shapero
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Daniel M Neumark
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.,Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
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Matthaei CT, Mukhopadhyay DP, Fischer I. Photodissociation of Benzoyl Chloride: A Velocity Map Imaging Study Using VUV Detection of Chlorine Atoms. J Phys Chem A 2021; 125:2816-2825. [PMID: 33819043 DOI: 10.1021/acs.jpca.0c11236] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
UV photodissociation of benzoyl chloride, Ph-CO-Cl, is associated with the loss of a chlorine atom. Here we excite benzoyl chloride to the S1, S2, and S3 excited states at 237, 253, 265, and 279.6 nm and detect the Cl photofragment by [1 + 1'] photoionization using 118.9 nm VUV radiation. The translational energy distribution of the Cl atom is measured by velocity map ion imaging. An isotropic image and a unimodal translational energy distribution are observed at all dissociation wavelengths, and a fraction of 18-20% of the excess energy is released into translation. The results indicate a dissociation that predominately proceeds from the vibrationally hot S0 ground state, although the observed translational energy release deviates significantly from a prior distribution. However, the impulsive model does also not represent the translational energy release. As a Cl/Cl* branching ratio of 9:1 or more is observed in one-color experiments at 235 nm, we conclude that direct dissociation from excited electronic states contributes only to a minor extent.
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Affiliation(s)
- Christian T Matthaei
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Deb Pratim Mukhopadhyay
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Ingo Fischer
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
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Chicharro DV, Zanchet A, Bouallagui A, Rubio-Lago L, García-Vela A, Bañares L, Marggi Poullain S. Site-specific hydrogen-atom elimination in photoexcited alkyl radicals. Phys Chem Chem Phys 2021; 23:2458-2468. [PMID: 33463638 DOI: 10.1039/d0cp05410k] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A prompt site-specific hydrogen-atom elimination from the α-carbon atom (Cα) has been recently reported to occur in the photodissociation of ethyl radicals following excitation at 201 nm [Chicharro et al., Chem. Sci., 2019, 10, 6494]. Such pathway was accessed by means of an initial ro-vibrational energy characterizing the radicals produced by in situ photolysis of a precursor. Here, we present experimental evidence of a similar dynamics in a series of alkyl radicals (C2H5, n-C3H7, n-C4H9, and i-C3H7) containing the same reaction coordinate, but different extended structures. The main requirements for the site-specific mechanism in the studied radicals, namely a rather high content of internal energy prior to dissociation and the participation of vibrational promoting modes, is discussed in terms of the chemical structure of the radicals. The methyl deformation mode in all alkyl radicals along with the CH bending motion in i-C3H7 appear to promote this fast H-atom elimination channel. The photodissociation dynamics of the simplest unsaturated alkyl radical, the vinyl radical (C2H3), is also discussed, showing no signal of site-specific fast H-atom elimination. The results are complemented with high-level ab initio electronic structure calculations of potential energy curves of the vinyl radical, which are compared with those previously reported for the ethyl radical.
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Affiliation(s)
- David V Chicharro
- Departamento de Química Física (Unidad Asociada I + D + i al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
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8
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Sun G, Zheng X, Song Y, Lucas M, Zhang J. Ultraviolet photodissociation dynamics of the n-butyl, s-butyl, and t-butyl radicals. J Chem Phys 2020; 152:244303. [PMID: 32610986 DOI: 10.1063/5.0012180] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Photodissociation dynamics of the jet-cooled n-butyl radical via the 3s Rydberg state and the s-butyl radical via the 3p Rydberg states in the ultraviolet region of 233 nm-258 nm, as well as the t-butyl radical via the 3d Rydberg states at 226 nm-244 nm, are studied using the high-n Rydberg atom time-of-flight technique. The H-atom photofragment yield spectra of the n-butyl, s-butyl, and t-butyl radicals show a broad feature centered around 247 nm, 244 nm, and 234 nm, respectively. The translational energy distributions of the H + C4H8 products, P(ET)'s, of the three radicals are bimodal, with a slow (low ET) component peaking at ∼6 kcal/mol and a fast (high ET) component peaking at ∼52 kcal/mol-57 kcal/mol, ∼43 kcal/mol, and ∼37 kcal/mol for n-butyl, s-butyl, and t-butyl, respectively. The fraction of the products' translational energy in the available energy, ⟨ fT⟩, is 0.31, 0.30, and 0.27 for n-butyl, s-butyl, and t-butyl, respectively. The H-atom product angular distributions of the slow component are isotropic for all three radicals, while those of the fast component are anisotropic for n-butyl and s-butyl with an anisotropy parameter β ∼ 0.7 and ∼ 0.3 and that of the fast component of t-butyl is nearly isotropic. The bimodal product translational energy and angular distributions indicate two dissociation pathways to the H + C4H8 products in these three radicals, a direct, prompt dissociation on the repulsive potential energy surface coupling with the Rydberg excited states, and a unimolecular dissociation of the hot radical on the ground electronic state after internal conversion from the Rydberg states.
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Affiliation(s)
- Ge Sun
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, USA
| | - Xianfeng Zheng
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, USA
| | - Yu Song
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, USA
| | - Michael Lucas
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, USA
| | - Jingsong Zhang
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, USA
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9
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Röder A, Petersen J, Issler K, Fischer I, Mitrić R, Poisson L. Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals, and Carbenes Using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations. J Phys Chem A 2019; 123:10643-10662. [DOI: 10.1021/acs.jpca.9b06346] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anja Röder
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
- LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - Jens Petersen
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Kevin Issler
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Ingo Fischer
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Roland Mitrić
- Institute of Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Lionel Poisson
- LIDYL, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France
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Sun G, Zheng X, Song Y, Zhang J. H-Atom Product Channel in the Ultraviolet Photodissociation of the Thiomethoxy Radical (CH 3S) via the B̃ 2A 2 State. J Phys Chem A 2019; 123:5849-5858. [DOI: 10.1021/acs.jpca.9b01791] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ge Sun
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | - Xianfeng Zheng
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | - Yu Song
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
| | - Jingsong Zhang
- Department of Chemistry, University of California at Riverside, Riverside, California 92521, United States
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Ashfold MNR, Ingle RA, Karsili TNV, Zhang J. Photoinduced C–H bond fission in prototypical organic molecules and radicals. Phys Chem Chem Phys 2019; 21:13880-13901. [DOI: 10.1039/c8cp07454b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We survey and assess current knowledge regarding the primary photochemistry of hydrocarbon molecules and radicals.
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Affiliation(s)
| | | | | | - Jingsong Zhang
- Department of Chemistry
- University of California at Riverside
- Riverside
- USA
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12
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Finney BA, Laufer AH, Anglada JM, Francisco JS. Spectroscopic characterization of the ethyl radical-water complex. J Chem Phys 2016; 145:144301. [DOI: 10.1063/1.4963869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Brian A. Finney
- Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907-1393, USA
| | - Allan H. Laufer
- Chemical Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-1070, USA
| | - Josep M. Anglada
- College of Arts and Sciences, University of Nebraska-Lincoln, 1223 Oldfather Hall, Lincoln, Nebraska 68588-0312, USA
- Departament de Química Biològica i Modelització Molecular, (IQAC—CSIC), Calle Jordi Girona 18, E-08034 Barcelona, Spain
| | - Joseph S. Francisco
- Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907-1393, USA
- College of Arts and Sciences, University of Nebraska-Lincoln, 1223 Oldfather Hall, Lincoln, Nebraska 68588-0312, USA
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