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Abstract
In this article, we review nonadiabatic molecular dynamics (NAMD) methods for modeling spin-crossover transitions. First, we discuss different representations of electronic states employed in the grid-based and direct NAMD simulations. The nature of interstate couplings in different representations is highlighted, with the main focus on nonadiabatic and spin-orbit couplings. Second, we describe three NAMD methods that have been used to simulate spin-crossover dynamics, including trajectory surface hopping, ab initio multiple spawning, and multiconfiguration time-dependent Hartree. Some aspects of employing different electronic structure methods to obtain information about potential energy surfaces and interstate couplings for NAMD simulations are also discussed. Third, representative applications of NAMD to spin crossovers in molecular systems of different sizes and complexities are highlighted. Finally, we pose several fundamental questions related to spin-dependent processes. These questions should be possible to address with future methodological developments in NAMD.
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Affiliation(s)
- Saikat Mukherjee
- Institut de Chimie Radicalaire, CNRS 7273, Aix-Marseille University, 13013 Marseille, France;
| | - Dmitry A Fedorov
- Oak Ridge Associated Universities, Oak Ridge, Tennessee 37830, USA;
| | - Sergey A Varganov
- Department of Chemistry, University of Nevada, Reno, Nevada 89557-0216, USA;
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2
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Dutta J, Mukherjee S, Naskar K, Ghosh S, Mukherjee B, Ravi S, Adhikari S. The role of electron-nuclear coupling on multi-state photoelectron spectra, scattering processes and phase transitions. Phys Chem Chem Phys 2020; 22:27496-27524. [PMID: 33283826 DOI: 10.1039/d0cp04052e] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present first principle based beyond Born-Oppenheimer (BBO) theory and its applications on various models as well as realistic spectroscopic and scattering processes, where the Jahn-Teller (JT) theory is brought in conjunction with the BBO approach on the phase transition of lanthanide complexes. Over one and half decades, our development of BBO theory is demonstrated with ab initio calculations on representative molecules of spectroscopic interest (NO2 radical, Na3 and K3 clusters, NO3 radical, C6H6+ and 1,3,5-C6H3F3+ radical cations) as well as triatomic reactive scattering processes (H+ + H2 and F + H2). Such an approach exhibits the effect of JT, Renner-Teller (RT) and pseudo Jahn-Teller (PJT) type of interactions. While implementing the BBO theory, we generate highly accurate diabatic potential energy surfaces (PESs) to carry out quantum dynamics calculation and find excellent agreement with experimental photoelectron spectra of spectroscopic systems and cross-sections/rate constants of scattering processes. On the other hand, such electron-nuclear couplings incorporated through JT theory play a crucial role in dictating higher energy satellite transitions in the dielectric function spectra of the LaMnO3 complex. Overall, this article thoroughly sketches the current perspective of the BBO approach and its connection with JT theory with various applications on physical and chemical processes.
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Affiliation(s)
- Joy Dutta
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
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3
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Mukherjee B, Naskar K, Mukherjee S, Ravi S, Shamasundar KR, Mukhopadhyay D, Adhikari S. Beyond Born-Oppenheimer constructed diabatic potential energy surfaces for F + H 2 reaction. J Chem Phys 2020; 153:174301. [PMID: 33167635 DOI: 10.1063/5.0021885] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
First principles based beyond Born-Oppenheimer theory has been implemented on the F + H2 system for constructing multistate global diabatic Potential Energy Surfaces (PESs) through the incorporation of Nonadiabatic Coupling Terms (NACTs) explicitly. The spin-orbit (SO) coupling effect on the collision process of the F + H2 reaction has been included as a perturbation to the non-relativistic electronic Hamiltonian. Adiabatic PESs and NACTs for the lowest three electronic states (12A', 22A', and 12A″) are determined in hyperspherical coordinates as functions of hyperangles for a grid of fixed values of the hyperradius. Jahn-Teller (JT) type conical intersections between the two A' states translate along C2v and linear geometries in F + H2. In addition, A' and A″ states undergo Renner-Teller (RT) interaction at collinear configurations of this system. Both JT and RT couplings are validated by integrating NACTs along properly chosen contours. Subsequently, we have solved adiabatic-to-diabatic transformation (ADT) equations to evaluate the ADT angles for constructing the diabatic potential matrix of F + H2, including the SO coupling terms. The newly calculated diabatic PESs are found to be smooth, single-valued, continuous, and symmetric and can be invoked for performing accurate scattering calculations on the F + H2 system.
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Affiliation(s)
- Bijit Mukherjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - Koushik Naskar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - Soumya Mukherjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - Satyam Ravi
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
| | - K R Shamasundar
- Department of Chemical Science, Indian Institute of Science Education and Research, Mohali, India
| | | | - Satrajit Adhikari
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India
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4
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De Fazio D, Cavalli S, Aquilanti V. Benchmark Quantum Mechanical Calculations of Vibrationally Resolved Cross Sections and Rate Constants on ab Initio Potential Energy Surfaces for the F + HD Reaction: Comparisons with Experiments. J Phys Chem A 2016; 120:5288-99. [PMID: 27186680 DOI: 10.1021/acs.jpca.6b01471] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dario De Fazio
- Istituto di Struttura della
Materia, Consiglio Nazionale delle Ricerche, 00016 Roma, Italy
| | - Simonetta Cavalli
- Dipartimento di Chimica,
Biologia e Biotecnologie, Università di Perugia, 06123 Perugia, Italy
| | - Vincenzo Aquilanti
- Dipartimento di Chimica,
Biologia e Biotecnologie, Università di Perugia, 06123 Perugia, Italy
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5
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Abstract
The nonadiabatic quantum dynamics and Coriolis coupling effect in chemical reaction have been reviewed, with emphasis on recent progress in using the time-dependent wave packet approach to study the Coriolis coupling and nonadiabatic effects, which was done by K. L. Han and his group. Several typical chemical reactions, for example, H+D(2), F+H(2)/D(2)/HD, D(+)+H(2), O+H(2), and He+H(2)(+), have been discussed. One can find that there is a significant role of Coriolis coupling in reaction dynamics for the ion-molecule collisions of D(+)+H(2), Ne+H(2)(+), and He+H(2)(+) in both adiabatic and nonadiabatic context.
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Affiliation(s)
- Emilia L Wu
- Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. S.E., Minneapolis, MN 55455-0132, USA.
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De Fazio D, Aquilanti V, Cavalli S, Aguilar A, Lucas JM. Exact state-to-state quantum dynamics of the F+HD→HF(v′=2)+D reaction on model potential energy surfaces. J Chem Phys 2008; 129:064303. [DOI: 10.1063/1.2964103] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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7
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De Fazio D, Cavalli S, Aquilanti V, Buchachenko AA, Tscherbul TV. On the Role of Scattering Resonances in the F + HD Reaction Dynamics. J Phys Chem A 2007; 111:12538-49. [DOI: 10.1021/jp0759473] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D. De Fazio
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy, Istituto di Metodologie Inorganiche e dei Plasmi - C.N.R., 70126 Bari, Italy, Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, 119992 Moscow, Russia, and Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, Canada
| | - S. Cavalli
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy, Istituto di Metodologie Inorganiche e dei Plasmi - C.N.R., 70126 Bari, Italy, Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, 119992 Moscow, Russia, and Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, Canada
| | - V. Aquilanti
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy, Istituto di Metodologie Inorganiche e dei Plasmi - C.N.R., 70126 Bari, Italy, Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, 119992 Moscow, Russia, and Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, Canada
| | - A. A. Buchachenko
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy, Istituto di Metodologie Inorganiche e dei Plasmi - C.N.R., 70126 Bari, Italy, Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, 119992 Moscow, Russia, and Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, Canada
| | - T. V. Tscherbul
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy, Istituto di Metodologie Inorganiche e dei Plasmi - C.N.R., 70126 Bari, Italy, Laboratory of Molecular Structure and Quantum Mechanics, Department of Chemistry, Moscow State University, 119992 Moscow, Russia, and Department of Chemistry, University of British Columbia, V6T 1Z1, Vancouver, Canada
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8
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Kłos JA, Dagdigian PJ, Alexander MH. Theoretical study of the multiplet branching of the SD product in the S(D1)+D2→SD(Π2)+D reaction. J Chem Phys 2007; 127:154321. [DOI: 10.1063/1.2790441] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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9
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Zolot AM, Nesbitt DJ. Quantum state resolved scattering dynamics of F+HCl→HF(v,J)+Cl. J Chem Phys 2007; 127:114319. [PMID: 17887849 DOI: 10.1063/1.2770464] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
State-to-state reaction dynamics of the reaction F+HCl-->HF(v,J)+Cl have been studied under single-collision conditions using an intense discharge F atom source in crossed supersonic molecular beams at Ecom=4.3(1.3) kcal/mol. Nascent HF product is monitored by shot-noise limited direct infrared laser absorption, providing quantum state distributions as well as additional information on kinetic energy release from high resolution Dopplerimetry. The vibrational distributions are highly inverted, with 34(4)%, 44(2)%, and 8(1)% of the total population in vHF=1, 2, and 3, respectively, consistent with predominant energy release into the newly formed bond. However, there is a small [14(1)%] but significant formation channel into the vHF=0 ground state, which is directly detectable for the first time via direct absorption methods. Of particular dynamical interest, both the HF(v=2,J) and HF(v=1,J) populations exhibit strongly bimodal J distributions. These results differ significantly from previous flow and arrested-relaxation studies and may signal the presence of microscopic branching in the reaction dynamics.
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Affiliation(s)
- A M Zolot
- JILA, National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA
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10
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De Fazio D, Aquilanti V, Cavalli S, Aguilar A, Lucas JM. Exact quantum calculations of the kinetic isotope effect: cross sections and rate constants for the F+HD reaction and role of tunneling. J Chem Phys 2007; 125:133109. [PMID: 17029435 DOI: 10.1063/1.2221695] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this paper we present integral cross sections (in the 5-220 meV collision energy range) and rate constants (in the 100-300 K range of temperature) for the F+HD reaction leading to HF+D and DF+H. The exact quantum reactive scattering calculations were carried out using the hyperquantization algorithm on an improved potential energy surface which incorporates the effects of open shell and fine structure of the fluorine atom in the entrance channel. The results reproduce satisfactorily molecular beam scattering experiments as well as chemical kinetics data for both the HF and DF channels. In particular, the agreement of the rate coefficients and the vibrational branching ratios with experimental measurements is improved with respect to previous studies. At thermal and subthermal energies, the rates are greatly influenced by tunneling through the reaction barrier. Therefore exchange of deuterium is shown to be penalized with respect to exchange of hydrogen, and the isotopic branching exhibits a strong dependence on translational energy. Also, it is found that rotational excitation of the reactant HD molecule enhances the production of HF and decreases the reactivity at the D end, obtaining insight on the reaction stereodynamics.
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Affiliation(s)
- Dario De Fazio
- Dipartimento di Chimica, Università di Perugia, 06123 Perugia, Italy.
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11
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12
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Abstract
A critical overview of the recent progress in crossed-beam reactive scattering is presented. This review is not intended to be an exhaustive nor a comprehensive one, but rather a critical assessment of what we have been learning about bimolecular reaction dynamics using crossed molecular beams since year 2000. Particular emphasis is placed on the information content encoded in the product angular distribution-the trait of a typical molecular beam scattering experiment-and how the information can help in answering fundamental questions about chemical reactivity. We will start with simple reactions by highlighting a few benchmark three-atom reactions, and then move on progressively to the more complex chemical systems and with more sophisticated types of measurements. Understanding what cause the experimental observations is more than computationally simulating the results. The give and take between experiment and theory in unraveling the physical picture of the underlying dynamics is illustrated throughout this review.
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Affiliation(s)
- Kopin Liu
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, Taipei 10617, Taiwan.
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13
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Dong F, Lee SH, Liu K. A crossed-beam study of the F+HD→DF+H reaction: The direct scattering channel. J Chem Phys 2006; 124:224312. [PMID: 16784279 DOI: 10.1063/1.2211612] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
State-to-state differential cross sections of the title reaction are presented at four collision energies, ranging from 1.18 to 4.0 kcal /mol. Product angular distributions are predominantly backscattered at low energies and shift toward sideways (peaking near 150 degrees ) at higher energies. Experimental evidence for contributions from migratory trajectories was found in the more detailed angle-specific internal state distributions. The dynamics of this reaction is mostly governed by classical mechanics, and several major findings can qualitatively be rationalized. These "classical" behaviors serve as "references" and are to be contrasted to the attributes observed for the other isotopic product channel, HF+D, in a forthcoming paper.
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Affiliation(s)
- Feng Dong
- Institute of Atomic and Molecular Sciences (IAMS), Academia Sinica, P.O. Box 23-166, Taipei 10617, Taiwan
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14
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Deskevich MP, Hayes MY, Takahashi K, Skodje RT, Nesbitt DJ. Multireference configuration interaction calculations for the F(P2)+HCl→HF+Cl(P2) reaction: A correlation scaled ground state (1A′2) potential energy surface. J Chem Phys 2006; 124:224303. [PMID: 16784270 DOI: 10.1063/1.2192505] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This paper presents a new ground state (1 (2)A(')) electronic potential energy surface for the F((2)P)+HCl-->HF+Cl((2)P) reaction. The ab initio calculations are done at the multireference configuration interaction+Davidson correction (MRCI+Q) level of theory by complete basis set extrapolation of the aug-cc-pVnZ (n=2,3,4) energies. Due to low-lying charge transfer states in the transition state region, the molecular orbitals are obtained by six-state dynamically weighted multichannel self-consistent field methods. Additional perturbative refinement of the energies is achieved by implementing simple one-parameter correlation energy scaling to reproduce the experimental exothermicity (DeltaE=-33.06 kcalmol) for the reaction. Ab initio points are fitted to an analytical function based on sum of two- and three-body contributions, yielding a rms deviation of <0.3 kcalmol for all geometries below 10 kcalmol above the barrier. Of particular relevance to nonadiabatic dynamics, the calculations show significant multireference character in the transition state region, which is located 3.8 kcalmol with respect to F+HCl reactants and features a strongly bent F-H-Cl transition state geometry (theta approximately 123.5 degrees ). Finally, the surface also exhibits two conical intersection seams that are energetically accessible at low collision energies. These seams arise naturally from allowed crossings in the C(infinityv) linear configuration that become avoided in C(s) bent configurations of both the reactant and product, and should be a hallmark of all X-H-Y atom transfer reaction dynamics between ((2)P) halogen atoms.
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Affiliation(s)
- Michael P Deskevich
- JILA, National Institute of Standards and Technology, University of Colorado, Boulder, Colorado 80309, USA
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15
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Zhang Y, Xie TX, Han KL, Zhang JZH. Nonadiabatic reactant-product decoupling calculation for the F(P1∕22)+H2 reaction. J Chem Phys 2006; 124:134301. [PMID: 16613449 DOI: 10.1063/1.2181985] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In this paper we present a theoretical study using time-dependent nonadiabatic reactant-product decoupling method for the state-to-state reactive scattering calculation of F((2)P(1/2))+H(2) (nu=j=0) reaction on the Alexander-Stark-Werner potential energy surface. In this nonadiabatic state-to-state calculation, the full wave function is partitioned into reactant component and a sum of all product components. The reactant and product components of the wave function are solved independently. For the excited state reaction, the state-to-state reaction probabilities for J=0.5 are calculated. Comparing the state-to-state reaction probabilities, it is found that the vibrational population of the HF product is dominated by vibrational levels nu=2 and 3. The rotation specific reaction probabilities of HF product in j=1 and 2 are larger than those in other rotational levels. As the rotation quantum number j increases, the positions of the peak in the rotational reaction probability of HF product in nu=3 shift to higher collision energy.
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Affiliation(s)
- Yan Zhang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian 116023, China
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16
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Chu TS, Zhang Y, Han KL. The time-dependent quantum wave packet approach to the electronically nonadiabatic processes in chemical reactions. INT REV PHYS CHEM 2006. [DOI: 10.1080/01442350600677929] [Citation(s) in RCA: 416] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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17
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Ziemkiewicz M, Wojcik M, Nesbitt DJ. Direct evidence for nonadiabatic dynamics in atom+polyatom reactions: Crossed-jet laser studies of F+D2O→DF+OD. J Chem Phys 2005; 123:224307. [PMID: 16375476 DOI: 10.1063/1.2098648] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Quantum-state-resolved reactive-scattering dynamics of F+D(2)O-->DF+OD have been studied at E(c.m.)=5(1) kcal/mol in low-density crossed supersonic jets, exploiting pulsed discharge sources of F atom and laser-induced fluorescence to detect the nascent OD product under single-collision conditions. The product OD is formed exclusively in the v(OD)=0 state with only modest rotational excitation (<E(rot)> =0.50(1) kcal/mol), consistent with the relatively weak coupling of the 18.1(1) kcal/mol reaction exothermicity into "spectator" bond degrees of freedom. The majority of OD products [68(1)%] are found in the ground ((2)Pi(32) (+/-)) spin-orbit state, which adiabatically correlates with reaction over the lowest and only energetically accessible barrier (DeltaE( not equal) approximately 4 kcal/mol). However, 32(1)% of molecules are produced in the excited spin-orbit state ((2)Pi(12) (+/-)), although from a purely adiabatic perspective, this requires passage over a DeltaE( not equal) approximately 25 kcal/mol barrier energetically inaccessible at these collision energies. This provides unambiguous evidence for nonadiabatic surface hopping in F+D(2)O atom abstraction reactions, indicating that reactive-scattering dynamics even in simple atom+polyatom systems is not always isolated on the ground electronic surface. Additionally, the nascent OD rotational states are well fitted by a two-temperature Boltzmann distribution, suggesting correlated branching of the reaction products into the DF(v=2,3) vibrational manifold.
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Affiliation(s)
- Michael Ziemkiewicz
- Joint Institute for Laboratory Astrophysics (JILA), National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0040, USA
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Rusin LY, Sevryuk MB, Toennies JP. Comparison of experimental time-of-flight spectra of the HF products from the F+H2 reaction with exact quantum mechanical calculations. J Chem Phys 2005; 122:134314. [PMID: 15847472 DOI: 10.1063/1.1873772] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
High resolution HF product time-of-flight spectra measured for the reactive scattering of F atoms from n-H2(p-H2) molecules at collision energies between 69 and 81 meV are compared with exact coupled-channel quantum mechanical calculations based on the Stark-Werner ab initio ground state potential energy surface. Excellent agreement between the experimental and computed rotational distributions is found for the HF product vibrational states v'=1 and v'=2. For the v'=3 vibrational state the agreement, however, is less satisfactory, especially for the reaction with p-H2. The results for v'=1 and v'=2 confirm that the reaction dynamics for these product states is accurately described by the ground electronic state 1 (2)A' potential energy surface. The deviations for HF(v'=3, j' > or =2) are attributed to an enhancement of the reaction resulting from the 25% fraction of excited ((2)P(12)) fluorine atoms in the reactant beam.
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Affiliation(s)
- Lev Yu Rusin
- Institute of Energy Problems of Chemical Physics, Russia Academy of Sciences, Leninskiî prospect 38, Building 2, Moscow 119334, Russia.
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19
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Tzeng YR, Alexander MH. Angular distributions for the F+H2→HF+H reaction: The role of the F spin-orbit excited state and comparison with molecular beam experiments. J Chem Phys 2004; 121:5812-20. [PMID: 15367007 DOI: 10.1063/1.1784446] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We report quantum mechanical calculations of center-of-mass differential cross sections (DCS) for the F+H(2)-->HF+H reaction performed on the multistate [Alexander-Stark-Werner (ASW)] potential energy surfaces (PES) that describe the open-shell character of this reaction. For comparison, we repeat single-state calculations with the Stark-Werner (SW) and Hartke-Stark-Werner (HSW) PESs. The ASW DCSs differ from those predicted for the SW and HSW PES in the backward direction. These differences arise from nonadiabatic coupling between several electronic states. The DCSs are then used in forward simulations of the laboratory-frame angular distributions (ADs) measured by Lee, Neumark, and co-workers [J. Chem. Phys. 82, 3045 (1985)]. The simulations are scaled to match experiment over the range 12 degrees <Theta(lab)<80 degrees. As a natural consequence of the reduced backward scattering, the ASW ADs are more forward and sideways scattered than predicted by the HSW PES. At the two higher collision energies (2.74 and 3.42 kcal/mol) the enhanced sideways scattering of HF v(')=2 products bring the ASW ADs in very good agreement with the experiment. At the lowest collision energy (1.84 kcal/mol), the simulations, for all three sets of PESs consistently underestimate the sideways scattering. The residual disagreements, particularly at the lowest collision energy, may be due to the known deficiencies in the PESs.
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Affiliation(s)
- Yi-Ren Tzeng
- Department of Biochemistry and Chemistry, Chemical Physics Program, University of Maryland, College Park, Maryland 20742-2021, USA
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Alexander MH, Rackham EJ, Manolopoulos DE. Product multiplet branching in the O(1D)+H2→OH(2Π)+H reaction. J Chem Phys 2004; 121:5221-35. [PMID: 15352815 DOI: 10.1063/1.1779574] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The statistical model of atom-diatom insertion reactions is combined with coupled-states capture theory and used to calculate product multiplet-resolved integral cross sections for the title reaction. This involves an ab initio determination of the four electronic potential energy surfaces that correlate with the products ((1,3)A(') and (1,3)A(")), and an accurate description of the electronic and spin-orbit couplings between them. The dependence of the resulting cross sections on the final-state rotational quantum number shows a statistical behavior similar to that observed in earlier studies of the reaction in which only the lowest ((1)A(')) potential was retained. In addition, however, the present calculations provide information on the branching between the OH((2)Pi) multiplet levels. Although the two spin-orbit manifolds are predicted to be equally populated, we find a strong propensity for the formation of the Pi(A(')) Lambda-doublet states. These two predictions confirm the experimental results of Butler, Wiesenfeld, Gericke, Brouard, and their co-workers. The nonstatistical population of the OH Lambda-doublet levels is a consequence of the bond breaking in the intermediate H(2)O complex and is preserved through the multiple curve crossings as the products separate. This exit-channel coupling is correctly described by the present theory.
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Affiliation(s)
- Millard H Alexander
- Department of Chemistry and Biochemistry and Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742-2021, USA
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