1
|
González-Vázquez J, García GA, Chicharro DV, Bañares L, Poullain SM. Evidencing an elusive conical intersection in the dissociative photoionization of methyl iodide. Chem Sci 2024; 15:3203-3213. [PMID: 38425510 PMCID: PMC10901492 DOI: 10.1039/d3sc04065h] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 12/23/2023] [Indexed: 03/02/2024] Open
Abstract
The valence-shell dissociative photoionization of methyl iodide (CH3I) is studied using double imaging photoelectron photoion coincidence (i2 PEPICO) spectroscopy in combination with highly-tunable synchrotron radiation from synchrotron SOLEIL. The experimental results are complemented by new high-level ab initio calculations of the potential energy curves of the relevant electronic states of the methyl iodide cation (CH3I+). An elusive conical intersection is found to mediate internal conversion from the initially populated first excited state, CH3I+(Ã2A1), into the ground cationic state, leading to the formation of methyl ions (CH3+). The reported threshold photoelectron spectrum for CH3+ reveals that the ν5 scissors vibrational mode promotes the access to this conical intersection and hence, the transfer of population. An intramolecular charge transfer takes place simultaneously, prior to dissociation. Upon photoionization into the second excited cationic state, CH3I+(B̃2E), a predissociative mechanism is shown to lead to the formation of atomic I+.
Collapse
Affiliation(s)
- Jesús González-Vázquez
- Departamento de Química, Facultad de Ciencias, Universidad Autónoma de Madrid Spain
- Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid 28049 Madrid Spain
| | - Gustavo A García
- Synchrotron SOLEIL L'Orme des Merisiers, St. Aubin, BP 48 91192 Gif-sur-Yvette France
| | - David V Chicharro
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid 28040 Madrid Spain
| | - Luis Bañares
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid 28040 Madrid Spain
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanoscience) Cantoblanco 28049 Madrid Spain
| | - Sonia Marggi Poullain
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid 28040 Madrid Spain
| |
Collapse
|
2
|
The role of predissociation states in the UV photooxidation of acetylene. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
3
|
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.
Collapse
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.
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Wang G, Liu T, Caracciolo A, Vansco MF, Trongsiriwat N, Walsh PJ, Marchetti B, Karsili TNV, Lester MI. Photodissociation dynamics of methyl vinyl ketone oxide: A four-carbon unsaturated Criegee intermediate from isoprene ozonolysis. J Chem Phys 2021; 155:174305. [PMID: 34742186 DOI: 10.1063/5.0068664] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The electronic spectrum of methyl vinyl ketone oxide (MVK-oxide), a four-carbon Criegee intermediate derived from isoprene ozonolysis, is examined on its second π* ← π transition, involving primarily the vinyl group, at UV wavelengths (λ) below 300 nm. A broad and unstructured spectrum is obtained by a UV-induced ground state depletion method with photoionization detection on the parent mass (m/z 86). Electronic excitation of MVK-oxide results in dissociation to O (1D) products that are characterized using velocity map imaging. Electronic excitation of MVK-oxide on the first π* ← π transition associated primarily with the carbonyl oxide group at λ > 300 nm results in a prompt dissociation and yields broad total kinetic energy release (TKER) and anisotropic angular distributions for the O (1D) + methyl vinyl ketone products. By contrast, electronic excitation at λ ≤ 300 nm results in bimodal TKER and angular distributions, indicating two distinct dissociation pathways to O (1D) products. One pathway is analogous to that at λ > 300 nm, while the second pathway results in very low TKER and isotropic angular distributions indicative of internal conversion to the ground electronic state and statistical unimolecular dissociation.
Collapse
Affiliation(s)
- Guanghan Wang
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Tianlin Liu
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Adriana Caracciolo
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Michael F Vansco
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Nisalak Trongsiriwat
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Patrick J Walsh
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Barbara Marchetti
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, Louisiana 70504, USA
| | - Tolga N V Karsili
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, Louisiana 70504, USA
| | - Marsha I Lester
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| |
Collapse
|
6
|
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.
Collapse
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
| |
Collapse
|
7
|
Parent LR, Gnanasekaran K, Korpanty J, Gianneschi NC. 100th Anniversary of Macromolecular Science Viewpoint: Polymeric Materials by In Situ Liquid-Phase Transmission Electron Microscopy. ACS Macro Lett 2021; 10:14-38. [PMID: 35548998 DOI: 10.1021/acsmacrolett.0c00595] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A century ago, Hermann Staudinger proposed the macromolecular theory of polymers, and now, as we enter the second century of polymer science, we face a different set of opportunities and challenges for the development of functional soft matter. Indeed, many fundamental questions remain open, relating to physical structures and mechanisms of phase transformations at the molecular and nanoscale. In this Viewpoint, we describe efforts to develop a dynamic, in situ microscopy tool suited to the study of polymeric materials at the nanoscale that allows for direct observation of discrete structures and processes in solution, as a complement to light, neutron, and X-ray scattering methods. Liquid-phase transmission electron microscopy (LPTEM) is a nascent in situ imaging technique for characterizing and examining solvated nanomaterials in real time. Though still under development, LPTEM has been shown to be capable of several modes of imaging: (1) imaging static solvated materials analogous to cryo-TEM, (2) videography of nanomaterials in motion, (3) observing solutions or nanomaterials undergoing physical and chemical transformations, including synthesis, assembly, and phase transitions, and (4) observing electron beam-induced chemical-materials processes. Herein, we describe opportunities and limitations of LPTEM for polymer science. We review the basic experimental platform of LPTEM and describe the origin of electron beam effects that go hand in hand with the imaging process. These electron beam effects cause perturbation and damage to the sample and solvent that can manifest as artefacts in images and videos. We describe sample-specific experimental guidelines and outline approaches to mitigate, characterize, and quantify beam damaging effects. Altogether, we seek to provide an overview of this nascent field in the context of its potential to contribute to the advancement of polymer science.
Collapse
Affiliation(s)
- Lucas R. Parent
- Innovation Partnership Building, The University of Connecticut, Storrs, Connecticut 06269, United States
| | | | | | | |
Collapse
|
8
|
Gao H. Molecular photodissociation in the vacuum ultraviolet region: implications for astrochemistry and planetary atmospheric chemistry. Mol Phys 2020. [DOI: 10.1080/00268976.2020.1861354] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Hong Gao
- Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing, People’s Republic of China
- University of Chinese Academy of Sciences, Beijing, People’s Republic of China
| |
Collapse
|
9
|
Varakin V. Photolysis of adsorbed polyatomic molecules on dielectric surfaces: General mechanisms. J Photochem Photobiol A Chem 2020. [DOI: 10.1016/j.jphotochem.2020.112850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
10
|
Chang Y, Yang J, Chen Z, Zhang Z, Yu Y, Li Q, He Z, Zhang W, Wu G, Ingle RA, Bain M, Ashfold MNR, Yuan K, Yang X, Hansen CS. Ultraviolet photochemistry of ethane: implications for the atmospheric chemistry of the gas giants. Chem Sci 2020; 11:5089-5097. [PMID: 34122966 PMCID: PMC8159213 DOI: 10.1039/d0sc01746a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 04/29/2020] [Indexed: 11/23/2022] Open
Abstract
Chemical processing in the stratospheres of the gas giants is driven by incident vacuum ultraviolet (VUV) light. Ethane is an important constituent in the atmospheres of the gas giants in our solar system. The present work describes translational spectroscopy studies of the VUV photochemistry of ethane using tuneable radiation in the wavelength range 112 ≤ λ ≤ 126 nm from a free electron laser and event-triggered, fast-framing, multi-mass imaging detection methods. Contributions from at least five primary photofragmentation pathways yielding CH2, CH3 and/or H atom products are demonstrated and interpreted in terms of unimolecular decay following rapid non-adiabatic coupling to the ground state potential energy surface. These data serve to highlight parallels with methane photochemistry and limitations in contemporary models of the photoinduced stratospheric chemistry of the gas giants. The work identifies additional photochemical reactions that require incorporation into next generation extraterrestrial atmospheric chemistry models which should help rationalise hitherto unexplained aspects of the atmospheric ethane/acetylene ratios revealed by the Cassini-Huygens fly-by of Jupiter.
Collapse
Affiliation(s)
- Yao Chang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Jiayue Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Zhichao Chen
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Zhiguo Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- Key Laboratory of Functional Materials and Devices for Informatics of Anhui Higher Education Institutions, School of Physics and Electronic Engineering, Fuyang Normal University Fuyang Anhui 236041 China
| | - Yong Yu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Qingming Li
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Zhigang He
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Weiqing Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Guorong Wu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Rebecca A Ingle
- Department of Chemistry, University College London London WC1H 0AJ UK
| | - Matthew Bain
- School of Chemistry, University of Bristol Bristol BS8 1TS UK
| | | | - Kaijun Yuan
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
| | - Xueming Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences 457 Zhongshan Road Dalian 116023 China
- Department of Chemistry, Southern University of Science and Technology Shenzhen 518055 China
| | | |
Collapse
|
11
|
Marggi Poullain S, Chicharro DV, Zanchet A, Rubio-Lago L, García-Vela A, Bañares L. The 3s versus 3p Rydberg state photodissociation dynamics of the ethyl radical. Phys Chem Chem Phys 2019; 21:23017-23025. [PMID: 31599893 DOI: 10.1039/c9cp04273c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The photodissociation dynamics of the ethyl radical following excitation into the 3s and 3p Rydberg states are revisited in a joint experimental and theoretical study. Two different methods to produce the ethyl radical, pyrolysis and in situ photolysis, are employed in order to modify the initial ro-vibrational energy distribution characterizing the ethyl radical beam. H-atom velocity map images following excitation of the radical at 243 nm and at 201 nm are presented and discussed along with ab initio potential energy curves focussing on the bridged C2v geometry. The reported results show that the dynamics following excitation to the 3s Rydberg state is insensitive to the initial internal energy of the parent radical, in contrast to the dynamics on the 3p Rydberg state, which is strongly modified. The role of the bridged C2v geometry on both photodynamics is highlighted and discussed.
Collapse
Affiliation(s)
- Sonia Marggi Poullain
- Departamento de Química, Módulo 13, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | | | | | | | | | | |
Collapse
|
12
|
Grotjahn R, Furche F, Kaupp M. Development and Implementation of Excited-State Gradients for Local Hybrid Functionals. J Chem Theory Comput 2019; 15:5508-5522. [DOI: 10.1021/acs.jctc.9b00659] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Robin Grotjahn
- Institut für Chemie, Theoretische Chemie/Quantenchemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, D-10623 Berlin, Germany
| | - Filipp Furche
- Department of Chemistry, University of California, Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025, United States
| | - Martin Kaupp
- Institut für Chemie, Theoretische Chemie/Quantenchemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, D-10623 Berlin, Germany
| |
Collapse
|