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Talbot JJ, Arias-Martinez JE, Cotton SJ, Head-Gordon M. Fantastical excited state optimized structures and where to find them. J Chem Phys 2023; 159:171102. [PMID: 37916588 DOI: 10.1063/5.0172015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Accepted: 10/16/2023] [Indexed: 11/03/2023] Open
Abstract
The quantum chemistry community has developed analytic forces for approximate electronic excited states to enable walking on excited state potential energy surfaces (PES). One can thereby computationally characterize excited state minima and saddle points. Always implicit in using this machinery is the fact that an excited state PES only exists within the realm of the Born-Oppenheimer approximation, where the nuclear and electronic degrees of freedom separate. This work demonstrates through ab initio calculations and simple nonadiabatic dynamics that some excited state minimum structures are fantastical: they appear to exist as stable configurations only as a consequence of the PES construct, rather than being physically observable. Each fantastical structure exhibits an unphysically high predicted harmonic frequency and associated force constant. This fact can serve as a valuable diagnostic of when an optimized excited state structure is non-observable. The origin of this phenomenon can be attributed to the coupling between different electronic states. As PESs approach one another, the upper surface can form a minimum that is very close to a near-touching point. The force constant, evaluated at this minimum, relates to the strength of the electronic coupling rather than to any characteristic excited state vibration. Nonadiabatic dynamics results using a Landau-Zener model illustrate that fantastical excited state structures have extremely short lifetimes on the order of a few femtoseconds. Their appearance in a calculation signals the presence of a nearby conical intersection through which the system will rapidly cross to a lower surface.
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Affiliation(s)
- Justin J Talbot
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA
| | - Juan E Arias-Martinez
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Stephen J Cotton
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA
| | - Martin Head-Gordon
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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2
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Kotsina N, Townsend D. Improved insights in time-resolved photoelectron imaging. Phys Chem Chem Phys 2021; 23:10736-10755. [DOI: 10.1039/d1cp00933h] [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
We review new light source developments and data analysis considerations relevant to the time-resolved photoelectron imaging technique. Case studies illustrate how these themes may enhance understanding in studies of excited state molecular dynamics.
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Affiliation(s)
- Nikoleta Kotsina
- Institute of Photonics & Quantum Sciences
- Heriot-Watt University
- Edinburgh
- UK
| | - Dave Townsend
- Institute of Photonics & Quantum Sciences
- Heriot-Watt University
- Edinburgh
- UK
- Institute of Chemical Sciences
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3
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Holt EL, Stavros VG. Applications of ultrafast spectroscopy to sunscreen development, from first principles to complex mixtures. INT REV PHYS CHEM 2019. [DOI: 10.1080/0144235x.2019.1663062] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Emily L. Holt
- Molecular Analytical Science Centre for Doctoral Training, Senate House, University of Warwick, Coventry, UK
- Department of Chemistry, University of Warwick, Coventry, UK
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4
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Wang QX, Shi DD, Zhang JF, Wang X, Si Y, Gao CB, Fang J, Luo SZ. Channel-resolved ultrafast dissociation dynamics of NO 2 molecules studied via femtosecond time-resolved ion imaging. CHINESE J CHEM PHYS 2019. [DOI: 10.1063/1674-0068/cjcp1807177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Qin-xin Wang
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
- Institute of Atomic and Molecular Physics and Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy, Jilin University, Changchun 130012, China
| | - Dan-dan Shi
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
| | - Jun-feng Zhang
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
| | - Xue Wang
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
| | - Yu Si
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
| | - Chun-bin Gao
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
| | - Jian Fang
- College of Electrical Engineering, Jilin Engineering Normal University, Changchun 130012, China
| | - Si-zuo Luo
- Institute of Atomic and Molecular Physics and Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy, Jilin University, Changchun 130012, China
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Kunin A, Neumark DM. Time-resolved radiation chemistry: femtosecond photoelectron spectroscopy of electron attachment and photodissociation dynamics in iodide-nucleobase clusters. Phys Chem Chem Phys 2019; 21:7239-7255. [PMID: 30855623 DOI: 10.1039/c8cp07831a] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Iodide-nucleobase (I-·N) clusters studied by time-resolved photoelectron spectroscopy (TRPES) are an opportune model system for examining radiative damage of DNA induced by low-energy electrons. By initiating charge transfer from iodide to the nucleobase and following the dynamics of the resulting transient negative ions (TNIs) with femtosecond time resolution, TRPES provides a novel window into the chemistry triggered by the attachment of low-energy electrons to nucleobases. In this Perspective, we examine and compare the dynamics of electron attachment, autodetachment, and photodissociation in a variety of I-·N clusters, including iodide-uracil (I-·U), iodide-thymine (I-·T), iodide-uracil-water (I-·U·H2O), and iodide-adenine (I-·A), to develop a more unified representation of our understanding of nucleobase TNIs. The experiments probe whether dipole-bound or valence-bound TNIs are formed initially and the subsequent time evolution of these species. We also provide an outlook for forthcoming applications of TRPES to larger iodide-containing complexes to enable the further investigation of microhydration dynamics in nucleobases, as well as electron attachment and photodissociation in more complex nucleic acid constituents.
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Affiliation(s)
- Alice Kunin
- Department of Chemistry, University of California, Berkeley, California 94720, USA.
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6
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Sala M, Egorova D. Imaging large amplitude out-of-plane motion in photoexcited pentafluorobenzene using time-resolved photoelectron spectroscopy: a computational study. Photochem Photobiol Sci 2018; 17:1036-1048. [PMID: 29999080 DOI: 10.1039/c8pp00051d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Excited-state dynamics of pentafluorobenzene is studied in detail for a quartic vibronic coupling model including the six b1 vibrational modes of the molecule and the two lowest excited electronic states. The study analyzes the influence of the large-amplitude out-of-plane vibrational motion on the electronic dynamics and extends to the simulation of the emerging time-resolved photoelectron spectra. The mapping of coherent non-separable electron-nuclear motion into oscillatory photoelectron signals is discussed.
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Affiliation(s)
- Matthieu Sala
- Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstr. 40, D-24098 Kiel, Germany.
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Wang Y, Liu Z, Xu Y, Zhang B. The geometrical change and intramolecular energy transfer upon S1←S0 excitation in cyclopentanone. J Chem Phys 2015; 143:064304. [PMID: 26277135 DOI: 10.1063/1.4928335] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The ultrafast dynamics in vibrationally hot S1 electronic excited state in cyclopentanone molecule was discovered with time resolved spectroscopy. Investigation of the geometry change upon the S1←S0 excitation and D0←S1 ionization has shown that the dihedral angle between the C=O bond and the plane given by the carbonyl and the α-carbons is 180° either in S0 or D0 state and is reduced to 145.8° by out-out-plane deformation of the oxygen in S1 state according to the theoretical calculation. The time domain experiments with femtosecond resolution have given rich insights into the energy transfer of the cyclopentanone molecule. The molecules are excited to the vibrationally hot S1 (n, π(∗)) state following absorption of one 267-nm photon. It is found that the population of the S1 (n, π(∗)) state undergoes ultrafast internal conversion to the highly vibrationally hot S0 state within 80 fs and nonradiative deactivation by intersystem crossing to triplet T1 (n, π(*)) state occurring in 3.14 ps. Several Rydberg states have worked as stepping stones during the ionization. The available energy was distributed in the symmetric methylene group wagging and the symmetric skeletal ring breathing modes in D0 state.
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Affiliation(s)
- Yanmei Wang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Zhiming Liu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Yanqi Xu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
| | - Bing Zhang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China
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8
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Dean JC, Kusaka R, Walsh PS, Allais F, Zwier TS. Plant Sunscreens in the UV-B: Ultraviolet Spectroscopy of Jet-Cooled Sinapoyl Malate, Sinapic Acid, and Sinapate Ester Derivatives. J Am Chem Soc 2014; 136:14780-95. [PMID: 25295994 DOI: 10.1021/ja5059026] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jacob C. Dean
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States
| | - Ryoji Kusaka
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States
| | - Patrick S. Walsh
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States
| | - Florent Allais
- AgroParisTech, Chaire Agro-Biotechnologies
Industrielles (ABI), 247
rue Paul Vaillant-Couturier, F-51100 Reims, France
- AgroParisTech, UMR 782 GMPA, Site de Grignon, F-78850 Thiverval-Grignon, France
- INRA, UMR 782 GMPA, Site de Grignon, F-78850 Thiverval-Grignon, France
| | - Timothy S. Zwier
- Department
of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States
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9
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Han S, Lim JS, Yoon JH, Lee J, Kim SY, Kim SK. Conical intersection seam and bound resonances embedded in continuum observed in the photodissociation of thioanisole-d3. J Chem Phys 2014; 140:054307. [DOI: 10.1063/1.4863449] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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10
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11
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De Giovannini U, Brunetto G, Castro A, Walkenhorst J, Rubio A. Simulating Pump-Probe Photoelectron and Absorption Spectroscopy on the Attosecond Timescale with Time-Dependent Density Functional Theory. Chemphyschem 2013; 14:1363-76. [DOI: 10.1002/cphc.201201007] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Indexed: 11/07/2022]
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13
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Affiliation(s)
- Ryan M. Young
- Department of Chemistry, University of California, Berkeley, California 94720,
United States
| | - Daniel M. Neumark
- Department of Chemistry, University of California, Berkeley, California 94720,
United States
- Chemical
Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California
94720, United States
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14
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Long J, Liu Y, Qin C, Zhang S, Zhang B. Real-time visualization of the dynamic evolution of CS2 4d and 6s Rydberg wave packet components. OPTICS EXPRESS 2011; 19:4542-4552. [PMID: 21369286 DOI: 10.1364/oe.19.004542] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The dynamic evolution of CS2 4d and 6s Rydberg wave packet components has been experimentally visualized via femtosecond time-resolved photoelectron imaging coupled with time-resolved mass spectroscopy. The temporal evolution of the four components of the prepared Rydberg wave packet is directly observed as time-dependent changes of the intensities of different parts in the main photoelectron peak. Furthermore, time-resolved photoelectron angular distributions (PADs) clearly reflect the different component characters of 4d and 6s molecular orbitals. The lifetime of Rydberg wave packets is determined to be about 830fs and their decay is attributed to predissociation. Our results suggest the possibility of directly visualizing and determining the amplitudes and relative phases of different electronic and vibrational wave packet components in polyatomic molecules.
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Affiliation(s)
- Jinyou Long
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences-Wuhan, National Laboratory for Optoelectronics, Wuhan, Hubei 430071, China
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15
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Baumgartner F, Helm H. Stark field control of nonadiabatic dynamics in triatomic hydrogen. PHYSICAL REVIEW LETTERS 2010; 104:103002. [PMID: 20366418 DOI: 10.1103/physrevlett.104.103002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Indexed: 05/29/2023]
Abstract
We show experimentally that an external electric field can be used to control the amplitudes of nonadiabatic paths taken by a dissociating molecule. In the example presented here, this control is achieved by Stark-field mixing in H(3) Rydberg states with different decay paths. The final state continuum is in each path formed by three-particle wave packets of slow neutral hydrogen atoms in their electronic ground state. Their momentum vector correlations show signs of interference, since the molecule can access the identical continuum via two distinctly different paths, involving different nonadiabatic coupling mechanisms. As an added feature a preferred alignment of the fragmentation plane in the laboratory frame emerges, corresponding to a selective dissociation of molecules oriented along the field direction.
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Affiliation(s)
- Frank Baumgartner
- Department of Physics, University of Freiburg, Stefan-Meier-Strasse 19, D-79104 Freiburg, Germany
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16
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Adams CL, Schneider H, Weber JM. Vibrational Autodetachment−Intramolecular Vibrational Relaxation Translated into Electronic Motion. J Phys Chem A 2010; 114:4017-30. [DOI: 10.1021/jp910675n] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- C. L. Adams
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
| | - H. Schneider
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
| | - J. M. Weber
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
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17
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Schneider H, Vogelhuber KM, Schinle F, Stanton JF, Weber JM. Vibrational Spectroscopy of Nitroalkane Chains Using Electron Autodetachment and Ar Predissociation. J Phys Chem A 2008; 112:7498-506. [DOI: 10.1021/jp800124s] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Holger Schneider
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165
| | - Kristen M. Vogelhuber
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165
| | - Florian Schinle
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165
| | - John F. Stanton
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165
| | - J. Mathias Weber
- JILA, NIST, and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, and Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165
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Stolow A, Underwood JG. Time-Resolved Photoelectron Spectroscopy of Nonadiabatic Dynamics in Polyatomic Molecules. ADVANCES IN CHEMICAL PHYSICS 2008. [DOI: 10.1002/9780470259498.ch6] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Abstract
Experiments are reviewed in which key problems in chemical dynamics are probed by experiments based on photodetachment and/or photoexcitation of negative ions. Examples include transition state spectroscopy of biomolecular reactions, spectroscopy of open shell van der Waals complexes, photodissociation of free radicals, and time-resolved dynamics in clusters. The experimental methods used in these investigations are described along with representative systems that have been studied.
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Affiliation(s)
- Daniel M Neumark
- Department of Chemistry,University of California, Berkeley, California 94720, USA.
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Wollenhaupt M, Engel V, Baumert T. FEMTOSECOND LASER PHOTOELECTRON SPECTROSCOPY ON ATOMS AND SMALL MOLECULES: Prototype Studies in Quantum Control. Annu Rev Phys Chem 2005; 56:25-56. [PMID: 15796695 DOI: 10.1146/annurev.physchem.56.092503.141315] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
▪ Abstract We review prototype studies in the area of quantum control with femtosecond lasers. We restrict this discussion to atoms and diatomics under gas-phase collision-free conditions to allow for a comparison between theory and experiment. Both the perturbative regime and the nonperturbative regime of the light-matter interaction are addressed. To that end, atomic/molecular beam techniques are combined together with femtosecond laser techniques and energy-resolved photoelectron spectroscopy and ion detection. Highly detailed information on the laser-induced quantum dynamics is extracted with the help of kinetic energy-resolved photoelectron spectroscopy.
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Affiliation(s)
- M Wollenhaupt
- Institut für Physik, Universität Kassel, D-34132 Kassel, Germany.
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Gräfe S, Scheidel D, Engel V, Henriksen NE, Møller KB. Approaches to Wave Packet Imaging Using Femtosecond Ionization Spectroscopy. J Phys Chem A 2004. [DOI: 10.1021/jp040230q] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Abstract
Nonadiabatic effects play an important role in many areas of physics and chemistry. The coupling between electrons and nuclei may, for example, lead to the formation of a conical intersection between potential energy surfaces, which provides an efficient pathway for radiationless decay between electronic states. At such intersections the Born-Oppenheimer approximation breaks down, and unexpected dynamical processes result, which can be observed spectroscopically. We review the basic theory required to understand and describe conical, and related, intersections. A simple model is presented, which can be used to classify the different types of intersections known. An example is also given using wavepacket dynamics simulations to demonstrate the prototypical features of how a molecular system passes through a conical intersection.
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Affiliation(s)
- Graham A Worth
- Department of Chemistry, King's College London, The Strand, London, WC2R 2LS, United Kingdom.
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Affiliation(s)
- Albert Stolow
- Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 Canada.
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Dantus M, Lozovoy VV. Experimental Coherent Laser Control of Physicochemical Processes. Chem Rev 2004; 104:1813-59. [PMID: 15080713 DOI: 10.1021/cr020668r] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marcos Dantus
- Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
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25
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Gräfe S, Engel V. Indirect versus direct photoionization with ultrashort pulses: interferences and time-resolved bond-length changes. Chem Phys Lett 2004. [DOI: 10.1016/j.cplett.2003.12.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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26
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Gessner O, Chrysostom ETH, Lee AMD, Wardlaw DM, Ho ML, Lee SJ, Cheng BM, Zgierski MZ, Chen IC, Shaffer JP, Hayden CC, Stolow A. Non-adiabatic intramolecular and photodissociation dynamics studied by femtosecond time-resolved photoelectron and coincidence imaging spectroscopy. Faraday Discuss 2004; 127:193-212. [PMID: 15471347 DOI: 10.1039/b316742a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Time-resolved photoelectron spectroscopy (TRPES) is emerging as a useful tool for the study of non-adiabatic dynamics in isolated polyatomic molecules and clusters due to its sensitivity to both electronic and vibrational dynamics. A powerful extension of TRPES, coincidence imaging spectroscopy (CIS), based upon femtosecond time-resolved 3D momentum vector imaging of both photoions and photoelectrons in coincidence, is a new technique for the study of complex dissociative processes. Here we show how these spectroscopies can be used to study both non-adiabatic intramolecular and photodissociation dynamics in polyatomic molecules. Intramolecular dynamics in the alpha, beta-enones acrolein, crotonaldehyde and methyl vinyl ketone are studied using both TRPES and laser-induced fluorescence of HCO(X) product yields. The location of the methyl group is seen to have very dramatic effects on the relative electronic relaxation rates and the HCO(X) yield. Applying both TRPES and CIS to the 200 nm and 209 nm photodissociation of the nitric oxide dimer, (NO)2, we observe the fs time-scale evolution of the excited parent neutral via its photoelectron spectrum and the emergence of the NO(A) photofragment including its energy and angular distributions.
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Affiliation(s)
- O Gessner
- Steacie Institute for Molecular Sciences, National Research Council, Ottawa ON, Canada
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