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G. Arcos C, García-Vela A, Sola IR. Impact of Early Coherences on the Control of Ultrafast Photodissociation Reactions. J Phys Chem Lett 2024; 15:1442-1448. [PMID: 38291810 PMCID: PMC10860130 DOI: 10.1021/acs.jpclett.3c03430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/22/2024] [Accepted: 01/26/2024] [Indexed: 02/01/2024]
Abstract
By coherent control, the yield of photodissociation reactions can be maximized, starting in a suitable superposition of vibrational states. In ultrafast processes, the interfering pathways are born from the early vibrational coherences in the ground electronic potential. We interpret their effect from a purely classical picture, in which the correlation between the initial position and momentum helps to synchronize the vibrational dynamics at the Franck-Condon window when the pulse is at its maximum intensity. In the quantum domain, we show that this localization in time and space is mediated by dynamic squeezing of the wave packet.
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Affiliation(s)
- Carlos G. Arcos
- Departamento
de Física Interdisciplinar, Universidad
Nacional de Educación a Distancia, 28232 Las Rozas, Spain
| | - Alberto García-Vela
- Instituto
de Física Fundamental, Consejo Superior
de Investigaciones Científicas, Serrano, 123, 28006 Madrid, Spain
| | - Ignacio R. Sola
- Departamento
de Química Física, Universidad
Complutense de Madrid, 28040 Madrid, Spain
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Jing WQ, Sun ZP, Zhao SF, Shu CC. Unveiling Coherent Control of Halomethane Dissociation Induced by a Single Strong Ultraviolet Pulse. J Phys Chem Lett 2023; 14:11305-11312. [PMID: 38064196 DOI: 10.1021/acs.jpclett.3c03143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
We present a theoretical investigation into the coherent control of photodissociation reactions in halomethanes, specifically focusing on CH2BrCl by manipulating the spectral phase of a single femtosecond laser pulse. We examine the photodissociation of CH2BrCl under an ultrashort pulse with a quadratic spectral phase and reveal the sensitivity of both the total dissociation probability and the resulting radical products (Br+CH2Cl and Cl+CH2Br) to chirp rates. To gain insights into the underlying mechanism, we calculate the population distributions of excited vibrational states in the ground electronic state, demonstrating the occurrence of resonance Raman scattering (RRS) in the strong-field limit regime. By utilizing chirped pulses, we show that this RRS phenomenon can be suppressed and even eliminated through quantum destructive interference. This highlights the high sensitivity of photodissociation into Cl+CH2Br to the spectral phase, showcasing a phenomenon that goes beyond the traditional one-photon photodissociation of isolated molecules in the weak-field limit regime. These findings emphasize the importance of coherent control in the exploration and utilization of photodissociation in polyatomic molecules, paving the way for new advancements in chemical physics and femtochemistry.
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Affiliation(s)
- Wen-Quan Jing
- College of Physics and Electronic Engineering, Northwest Normal University, Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, Lanzhou 730070, China
- Hunan Key Laboratory of Super-Microstructure and Ultrafast Process, School of Physics, Central South University, Changsha 410083, China
| | - Zhao-Peng Sun
- Institute of Theoretical Physics, School of Physics and Optoelectric Engineering, Ludong University, Yantai 264025, China
| | - Song-Feng Zhao
- College of Physics and Electronic Engineering, Northwest Normal University, Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, Lanzhou 730070, China
| | - Chuan-Cun Shu
- Hunan Key Laboratory of Super-Microstructure and Ultrafast Process, School of Physics, Central South University, Changsha 410083, China
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García-Vela A. Photodissociation of the methyl radical: the role of nonadiabatic couplings in enhancing the variety of dissociation mechanisms. Phys Chem Chem Phys 2021; 23:25911-25924. [PMID: 34780593 DOI: 10.1039/d1cp03293c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nonadiabatic photodissociation dynamics of the CH3 (and CD3) radical from the 3pz and 3s Rydberg states is investigated by applying a one-dimensional (1D) wave packet model that uses recently calculated ab initio 1D electronic potential-energy curves and nonadiabatic couplings. Calculated predissociation lifetimes are found to be too long as compared to the experimental ones. The 1D dynamical model, however, is able to predict qualitatively and explain the fragmentation mechanisms that produce the hydrogen-fragment translational energy distributions (TED) measured experimentally for the ground vibrational resonance of the 3pz and 3s Rydberg states (CH3(v = 0, 3pz) and CH3(v = 0, 3s)). The CH3(v = 0, 3pz) TED found experimentally displays a rather large energy spreading, while the experimental CH3(v = 0, 3s) TED is remarkably more localized in energy. The present model also predicts a widely spread CH3(v = 0, 3pz) TED, produced by a complex dissociation mechanism which involves predissociation to one dissociative valence state through a nonadiabatic coupling, as well as transfer of population to a second valence state through three conical intersections. Also in agreement with experiment, the model predicts a rather localized CH3(v = 0, 3s) TED because the conical intersections no longer operate in this photodissociation process, and predissociation occurs only into a single valence state. Another complex dissociation mechanism is predicted by the model for initial CH3(v > 0, 3s) and CD3(v > 0, 3s) resonances. In this case the mechanism is gradually activated, as vibrational excitation increases, by the interplay between the two nonadiabatic couplings connecting the 3s and 3px,y Rydberg states with the dissociative 2A1 valence state, and produces complex TEDs with signals from several resonances of both 3s and 3px,y. Thus the present 1D quantum model reveals a rich photodissociation dynamics of methyl, where a variety of complex fragmentation mechanisms is favored by the presence of different nonadiabatic couplings between the electronic states involved.
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Affiliation(s)
- A García-Vela
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
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Császár AG, Simkó I, Szidarovszky T, Groenenboom GC, Karman T, van der Avoird A. Rotational-vibrational resonance states. Phys Chem Chem Phys 2020; 22:15081-15104. [PMID: 32458891 DOI: 10.1039/d0cp00960a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Resonance states are characterized by an energy that is above the lowest dissociation threshold of the potential energy hypersurface of the system and thus resonances have finite lifetimes. All molecules possess a large number of long- and short-lived resonance (quasibound) states. A considerable number of rotational-vibrational resonance states are accessible not only via quantum-chemical computations but also by spectroscopic and scattering experiments. In a number of chemical applications, most prominently in spectroscopy and reaction dynamics, consideration of rotational-vibrational resonance states is becoming more and more common. There are different first-principles techniques to compute and rationalize rotational-vibrational resonance states: one can perform scattering calculations or one can arrive at rovibrational resonances using variational or variational-like techniques based on methods developed for determining bound eigenstates. The latter approaches can be based either on the Hermitian (L2, square integrable) or non-Hermitian (non-L2) formalisms of quantum mechanics. This Perspective reviews the basic concepts related to and the relevance of shape and Feshbach-type rotational-vibrational resonance states, discusses theoretical methods and computational tools allowing their efficient determination, and shows numerical examples from the authors' previous studies on the identification and characterization of rotational-vibrational resonances of polyatomic molecular systems.
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Affiliation(s)
- Attila G Császár
- MTA-ELTE Complex Chemical Systems Research Group, P. O. Box 32, H-1518 Budapest 112, Hungary.
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García-Vela A. Interference of a resonance state with itself: a route to control its dynamical behaviour. Phys Chem Chem Phys 2020; 22:14637-14644. [PMID: 32572415 DOI: 10.1039/d0cp00392a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It is demonstrated both numerically and mathematically that the dynamical behavior of an isolated resonance state, which comprises the resonance decay lifetime and the asymptotic fragment state distribution produced upon resonance decay, can be extensively controlled by means of quantum interference induced by a laser field in the weak-field regime. The control scheme applied is designed to induce interference between amplitudes excited at two different energies of the resonance line shape, namely the resonance energy and an additional energy. This scheme exploits the resonance property of possessing a nonzero energy width, which makes it possible that a resonance state may interfere with itself, and thus allows interference between the amplitudes excited at the two energies of the resonance width. The application of this scheme opens the possibility of a universal control of both the duration and the fragment product distribution outcome of any resonance-mediated molecular process.
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Affiliation(s)
- A García-Vela
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
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Abstract
A weak-field coherent control scheme is applied in order to enhance the decay lifetime of a superposition of overlapping resonance states. The scheme uses a pump laser field consisting of two pulses delayed in time, each of them exciting a different energy at which several resonances of the Ne-Br2(B) complex overlap. Simultaneous excitation of these two energies induces interference between the overlapping resonances, which causes an enhancement of the lifetime of the superposition created. By variation of the delay time between the pulses, the mechanism of resonance interference can be controlled and optimized to achieve a maximum lifetime enhancement. The optimal delay time between pulses leading to maximum superposition lifetime can be quantitatively predicted with a simple law. The effect of the interference mechanism on the lifetime enhancement is investigated. It is found that interference induces a transfer of amplitude between the different resonances back and forth, which delays significantly the natural resonance decay, increasing the global lifetime of the superposition. Due to the simplicity of the control scheme, a wide applicability is envisioned.
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Affiliation(s)
- A García-Vela
- Instituto de Física Fundamental , Consejo Superior de Investigaciones Científicas , Serrano 123 , 28006 Madrid , Spain
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Serrano-Jiménez A, Bañares L, García-Vela A. Weak-field coherent control of photodissociation in polyatomic molecules. Phys Chem Chem Phys 2019; 21:7885-7893. [PMID: 30916089 DOI: 10.1039/c9cp01214a] [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
A coherent control scheme is suggested to modify the output of photodissociation in a polyatomic system. The performance of the scheme is illustrated by applying it to the ultrafast photodissociation of CH3I in the A-band. The control scheme uses a pump laser weak field that combines two pulses of a few femtoseconds delayed in time. By varying the time delay between the pulses, the shape of the laser field spectral profile is modulated, which causes a change in the initial relative populations excited by the pump laser to the different electronic states involved in the photodissociation. Such a change in the relative populations produces different photodissociation outputs, which is the basis of the control achieved. The degree of control obtained over different photodissociation observables, like the branching ratio between the two dissociation channels of CH3I yielding I(2P3/2) and I*(2P1/2) and the fragment angular distributions associated with each channel, is investigated. These magnitudes are found to oscillate strongly with the time delay, with the branching ratio changing by factors between two and three. Substantial variations of the angular distributions also indicate that the scheme provides a high degree of control. Experimental application of the scheme to general polyatomic photodissociation processes should be straightforward.
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Affiliation(s)
- A Serrano-Jiménez
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
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García-Vela A. A unified theory of weak-field coherent control of the behavior of a resonance state. Phys Chem Chem Phys 2019; 21:7491-7501. [PMID: 30892329 DOI: 10.1039/c9cp01014a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A unified weak-field control scheme to modify the two properties that determine the whole behavior of a resonance state, namely the lifetime and the asymptotic fragment distribution produced upon resonance decay, is proposed. Control is exerted through quantum interference induced between overlapping resonances of the system, by exciting two different energies at which the resonances overlap. The scheme applies a laser field consisting of a first pulse that excites the energy of the resonance to be controlled, and two additional pulses that excite another different energy to induce interference, with a delay time with respect to the first pulse. Each of the two additional pulses is used to control one of the two resonance properties, by adjusting its corresponding delay time: with a relatively short delay time the second pulse controls the resonance lifetime, while with a very long delay time the third pulse modifies the asymptotic fragment distribution produced. The efficiency of the control of each resonance property is found to be strongly dependent on the choice of the second interfering energy, which allows for a more flexible control optimization by choosing a different energy for each property. The theory underlying the interference mechanism of the control scheme is developed and presented, and is applied to analyze and explain the results obtained. The present scheme thus appears to be a useful tool for controlling resonance-mediated molecular processes.
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Affiliation(s)
- A García-Vela
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 123, 28006 Madrid, Spain.
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Affiliation(s)
- Jian-wei Cao
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Feng-yi Li
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wen-sha Xia
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wen-sheng Bian
- Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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