Browsing by Author "Mineo, Hirobumi"

Now showing 1 - 15 of 15

Coherent ring currents in chiral aromatic molecules induced by linearly polarized UV laser pulses
(2013)
Kanno, Manabu
;
Kono, Hirohiko
;
Mineo, Hirobumi
;
Lin, Sheng Hsien
;
Fujimura, Yuichi
Dynamic Stark-Induced Coherent pi-Electron Rotations in a Chiral Aromatic Ring Molecule: Application to Phenylalanine
(2019-08-01)
Mineo, Hirobumi
;
Kim, Gap-Sue
;
Lin, Sheng Hsien
;
Fujimura, Yuichi
;
應用化學系分子科學碩博班
We present the results of a theoretical study on dynamic Stark-induced coherent pi-electron rotations in a chiral aromatic ring molecule. This is an extension of our previous papers, which have been published in Mineo, H. et al. [Phys. Chem. Chem. Phys. 2016, 18, 26786-26795] and Mineo, H. et al. [J. Phys. Chem. Lett. 2018, 9, 5521-5526]. In those papers, the time-dependent Schrodinger equation was solved under a restricted condition in which a degenerate excited state should be formed at the center of the two relevant excited states by dynamic Stark effects. The dynamic Stark-induced degenerate state (DSIDS) is essential to create unidirectional pi-electron rotations. In the present theoretical treatment, the above restriction is relaxed and the DSIDS is set to be at any energy position between the two excited states. This indicates a wide applicability of the dynamic Stark effects to coherent control of photophysical properties in aromatic molecules, such as coherent ring currents and current-induced magnetic fluxes of low-symmetric aromatic molecules. Analytical expressions for the coherent pi-electron angular momentum are derived within a three-electronic-state model by using the Laplace transform method. The validity of the developed theoretical procedure is demonstrated by carrying out simulations of the coherent angular momentum of L-phenylalanine. Effects of varying the DSIDS on the time-dependent coherent angular momentum and the populations in the three electronic states are examined, and the results are analyzed using approximate expressions for the time-dependent coherent angular momentum and the populations. Modulations in the time-dependent coherent angular momentum appear when the DSIDS is set at an energy position between the two excited states, while there are no beating modulations when the DSIDS is set at the center position. Such differences originate from whether interferences between the two dressed states take place or not.
Induction of unidirectional pi-electron rotations in low-symmetry aromatic ring molecules using two linearly polarized stationary lasers
(2016-10-14)
Mineo, Hirobumi
;
Yamaki, Masahiro
;
Kim, Gap-Sue
;
Teranishi, Yoshiaki
;
Lin, Sheng Hsien
A new laser-control scenario of unidirectional p-electron rotations in a low-symmetry aromatic ring molecule having no degenerate excited states is proposed. This scenario is based on dynamic Stark shifts of two relevant excited states using two linearly polarized stationary lasers. Each laser is set to selectively interact with one of the two electronic states, the lower and higher excited states are shifted up and down with the same rate, respectively, and the two excited states become degenerate at their midpoint. One of the four control parameters of the two lasers, i.e. two frequencies and two intensities, determines the values of all the other parameters. The direction of p-electron rotations, clockwise or counter-clockwise rotation, depends on the sign of the relative phase of the two lasers at the initial time. An analytical expression for the time-dependent expectation value of the rotational angular momentum operator is derived using the rotating wave approximation (RWA). The control scenario depends on the initial condition of the electronic states. The control scenario with the ground state as the initial condition was applied to toluene molecules. The derived time-dependent angular momentum consists of a train of unidirectional angular momentum pulses. The validity of the RWA was checked by numerically solving the time-dependent Schrodinger equation. The simulation results suggest an experimental realization of the induction of unidirectional p-electron rotations in low-symmetry aromatic ring molecules without using any intricate quantum-optimal control procedure. This may open up an effective generation method of ring currents and current-induced magnetic fields in biomolecules such as amino acids having aromatic ring molecules for searching their interactions.
Ionization and Dissociation Processes of Pyrrolidine in Intense Femtosecond Laser Field
(2009-07-09)
Wang, Qiaoqiao
;
Wu, Di
;
Zhang, Dongdong
;
Jin, Mingxing
;
Liu, Fuchun
Ionization and dissociation mechanisms of pyrrolidine in intense 800 nm laser field (10(13) to 10(14) W/cm(2)) have been experimentally investigated by using a method of molecular beam and time-of-flight mass spectrometer. Singly charged parent ion and numerous fragment ions are observed in the mass spectra, which are investigated as a function of laser intensity and polarization. In order to understand the details of the ionization processes of pyrrolidine in intense femtosecond laser field, we quantitatively calculate the rate constants and ion yields by means of generalized Keldysh-Faisal-Reiss theory, and the excitation probabilities of the excited states are also calculated by using Floquet theory. The results suggest that the ionization might occur partially through the excited states of neutral pyrrolidine. Comparing with linearly polarized (LP) laser field, we observe some enhancement of fragmentation with a circularly polarized (CP) laser field above the saturation threshold intensity which might be explained by the active energies of the pyrrolidine molecular ions are different under CP and LP laser irradiated. To interpret the dissociation patterns of the pyrrolidine ions, we have used the Rice-Ramsperger-Kassel-Marcus theory with the potential surfaces obtained from the ab initio quantum chemical calculations.
Ionization/dissociation processes of methyl-substituted derivates of cyclopentanone in intense femtosecond laser field
(2013-10-24)
Wang, Qiaoqiao
;
Dyakov, Yuri A.
;
Wu, Di
;
Zhang, Dongdong
;
Jin, Mingxing
Ionization and dissociation of 2- and 3-methyl cyclopentanones have been investigated in molecular beams by their irradiation with intense 394 and 788 nm laser fields with pulse duration of 90 fs and intensity of 3 x 10(13)-4 x 10(14) W/cm(2). The analysis of the resulting mass spectra allowed us to discern the effects of methyl substitution and its position on the outcome of ionization/dissociation processes induced by the intense femtosecond laser field. Generalized Keldysh-Faisal-Reiss (g-KFR) and ab initio G3(MP2, CCSD)//B3LYP/6-31G*/RRKM theoretical calculations helped to uncover the formation mechanism of major ionic fragments observed in the mass spectra including C5H10+, C4H6O+, C3H3O+, C3H4O+, C3Hx+, and C2Hx+. (C) 2013 Elsevier B.V. All rights reserved.
On the validity of the independent interaction model for generation of dynamic Stark-induced degenerate states in chiral aromatic ring molecules
(2020-02-16)
Mineo, Hirobumi
;
Kim, Gap-Sue
;
Lin, Sheng Hsien
;
Fujimura, Yuichi
;
應用化學系
Dynamic Stark-induced degenerate state (DSIDS) is essential to generate electronic coherent angular momentum to identify molecular chirality. We previously derived DSIDS for phenylalanine enantiomers in the independent interaction model (IIM), in which two linearly polarized nonresonant UV lasers independently interact with relevant two electronic excited states. We present a numerical method to derive DSIDS beyond IIM. Here, both lasers interact with both excited states, and laser input parameters are determined for DSIDS located at the center of the excited states. The numerical results reasonably agree with those calculated in the IIM, which elucidate the validity of DSIDS in the IIM.
Quantum coherent pi-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse
(2015-01-01)
Mineo, Hirobumi
;
Fujimura, Yuichi
;
應用化學系分子科學碩博班
;
Institute of Molecular science
We propose an ultrafast quantum switching method of pi-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2'-biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent pi-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasi-degenerated excited states. We also plot the time-dependent pi-electron ring current, and discussed ring current transfer between two aromatic rings.
Quantum Control of Coherent -Electron Dynamics in Chiral Aromatic Molecules
(2016-01)
Yamaki, Masahiro
;
Mineo, Hirobumi
;
Teranishi, Yoshiaki
;
Lin, Sheng Hsien
;
Fujimura, Yuichi
Control of mobile -electrons is one of the fundamental issues in the organic optoelectronics for designing the next generation ultrafast switching devices. The optimal control simulations of coherent -electron rotations in (P)-2,2\'-biphenol, which is the typical nonplanar aromatic molecule with axial chirality, were performed by taking into account two types of the control targets: one is generation of the maximum -angular momentum, and the other is the maintaining of the generated unidirectional angular momentum during a setting time duration. The optimal control pulse for each target is designed. The analysis of the simulation results shows that the effective maintaining of the unidirectional angular momentum can be realized by applying 2 pulse to one of the electronic excited states forming the coherent electronic state. The 2 pulse prevents the reverse rotation of the -electrons by dumping the excited state population to the ground state and subsequently by pumping the population back to the excited state. The present results provide a theoretical basis for the designing next generation ultrafast switching devices made by organic aromatic molecules.
Quantum Control of Coherent -Electron Dynamics in Chiral Aromatic Molecules
(2016-01-01)
Yamaki, Masahiro
;
Mineo, Hirobumi
;
Teranishi, Yoshiaki
;
Lin, Sheng Hsien
;
Fujimura, Yuichi
Control of mobile -electrons is one of the fundamental issues in the organic optoelectronics for designing the next generation ultrafast switching devices. The optimal control simulations of coherent -electron rotations in (P)-2,2\'-biphenol, which is the typical nonplanar aromatic molecule with axial chirality, were performed by taking into account two types of the control targets: one is generation of the maximum -angular momentum, and the other is the maintaining of the generated unidirectional angular momentum during a setting time duration. The optimal control pulse for each target is designed. The analysis of the simulation results shows that the effective maintaining of the unidirectional angular momentum can be realized by applying 2 pulse to one of the electronic excited states forming the coherent electronic state. The 2 pulse prevents the reverse rotation of the -electrons by dumping the excited state population to the ground state and subsequently by pumping the population back to the excited state. The present results provide a theoretical basis for the designing next generation ultrafast switching devices made by organic aromatic molecules.
Quantum control of coherent pi-electron ring currents in polycyclic aromatic hydrocarbons
(2017-12-14)
Mineo, Hirobumi
;
Fujimura, Yuichi
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
We present results for quantum optimal control (QOC) of the coherent pi electron ring currents in polycyclic aromatic hydrocarbons (PAHs). Since PAHs consist of a number of condensed benzene rings, in principle, there exist various coherent ring patterns. These include the ring current localized to a designated benzene ring, the perimeter ring current that flows along the edge of the PAH, and the middle ring current of PAHs having an odd number of benzene rings such as anthracene. In the present QOC treatment, the best target wavefunction for generation of the ring current through a designated path is determined by a Lagrange multiplier method. The target function is integrated into the ordinary QOC theory. To demonstrate the applicability of the QOC procedure, we took naphthalene and anthracene as the simplest examples of linear PAHs. The mechanisms of ring current generation were clarified by analyzing the temporal evolutions of the electronic excited states after coherent excitation by UV pulses or (UV+IR) pulses as well as those of electric fields of the optimal laser pulses. Time-dependent simulations of the perimeter ring current and middle ring current of anthracene, which are induced by analytical electric fields of UV pulsed lasers, were performed to reproduce the QOC results. Published by AIP Publishing.
Quantum Design for Ultrafast Probing of Molecular Chirality through Enantiomer-Specific Coherent pi-Electron Angular Momentum
(2018-09-20)
Mineo, Hirobumi
;
Kim, Gap-Sue
;
Lin, Sheng Hsien
;
Fujimura, Yuichi
;
應用化學系
Probing molecular chirality, right-handed or left-handed chiral molecules, is one of the central issues in chemistry and biochemistry. The conventional theory of optical activity measurements such as circular dichroism has been derived in the second-order processes involving electric and magnetic dipole moments, and the signals are very weak. We propose an efficient enantiomer-probing scenario for chiral aromatic ring molecules based on photoinduced coherent pi-electron rotations. In our model, the resultant laser-induced currents themselves produce a strong magnetic field. The principle for probing molecular chirality is a utilization of dynamic Stark effects of two electronic excited states. These electronic states subjected to strong nonresonant linearly polarized UV lasers become degenerate to create enantiomer-specific electronic angular momentum. A pair of enantiomers of phenylalanine was taken as an example. Enantiomer-specific coherent magnetic fluxes on the order of a few teslas can be generated in several tens of femtoseconds. The direct detection of strong coherent magnetic fluxes could be carried out by time-resolved magnetic force microscopy experiments. The results provide important implications for the measurement of effective probing of chiral aromatic molecules.
Quantum Design of pi-Electron Ring Currents in Polycyclic Aromatic Hydrocarbons: Parallel and Antiparallel Ring Currents in Naphthalene
(2017-05-04)
Mineo, Hirobumi
;
Fujimura, Yuichi
;
應用化學系分子科學碩博班
;
Institute of Molecular science
Control of pi-electrons in polycyclic aromatic hydrocarbons (PAHs) is one of the fundamental issues in optoelectronics for ultrafast optical switching devices. We have proposed an effective scenario for design of the generation of coherent ring currents in naphthalene (D-2h), which is the smallest, unit of planar PAHs. It has been demonstrated by using quantum chemical calculations and quantum optimal control (QOC) simulations that two types of ring currents, parallel and antiparallel, can be generated by resonance excitations by two linearly polarized lasers. A parallel (antiparallel) ring current means that the currents of two benzene rings run in the same (opposite) directions. The two types of ring currents may be experimentally identified by magnetic force microscopy. The QOC simulations indicate that a parallel ring current can be generated by using continuous wave and Gaussian pulse lasers with their time delay without relying on a sophisticated experimental apparatus. The present results provide a guiding principle of coherent it-electronics in PAHs for next-generation organic optical switching devices.
Quantum Localization of Coherent pi-Electron Angular Momentum in (P)-2,2 '-Biphenol
(2014-06-05)
Yamaki, Masahiro
;
Mineo, Hirobumi
;
Teranishi, Yoshiaki
;
Hayashi, Michitoshi
;
Fujimura, Yuichi
Controlling g-electrons with delocalized character is one of the fundamental issues in femtosecond and attosecond chemistry. Localization of pi-electron rotation by using laser pulses is expected to play an essential role in nanoscience. The pi-electron rotation created at a selected aromatic ring of a single molecule induces a local intense electromagnetic field, which is a new type of ultrafast optical control functioning. We propose a quantum localization of coherent pi-electron angular momentum in (P)-2,2'-biphenol, which is a simple, covalently linked chiral aromatic ring chain molecule. The localization considered here consists of sequential two steps: the first step is to localize the pi-electron angular momentum at a selected ring of the two benzene rings, and the other is to maintain the localization. Optimal control theory was used for obtaining the optimized electric fields of linearly polarized laser pulses to realize the localization. The optimal electric fields and the resultant coherent electronic dynamics are analyzed.
Quantum Localization of Coherent pi-Electron Angular Momentum in (P)-2,2 \'-Biphenol
(2014-06-05)
Yamaki, Masahiro
;
Mineo, Hirobumi
;
Teranishi, Yoshiaki
;
Hayashi, Michitoshi
;
Fujimura, Yuichi
Controlling g-electrons with delocalized character is one of the fundamental issues in femtosecond and attosecond chemistry. Localization of pi-electron rotation by using laser pulses is expected to play an essential role in nanoscience. The pi-electron rotation created at a selected aromatic ring of a single molecule induces a local intense electromagnetic field, which is a new type of ultrafast optical control functioning. We propose a quantum localization of coherent pi-electron angular momentum in (P)-2,2\'-biphenol, which is a simple, covalently linked chiral aromatic ring chain molecule. The localization considered here consists of sequential two steps: the first step is to localize the pi-electron angular momentum at a selected ring of the two benzene rings, and the other is to maintain the localization. Optimal control theory was used for obtaining the optimized electric fields of linearly polarized laser pulses to realize the localization. The optimal electric fields and the resultant coherent electronic dynamics are analyzed.
Quantum Switching of pi-Electron Rotations in a Nonplanar Chiral Molecule by Using Linearly Polarized UV Laser Pulses
(2012-09-05)
Mineo, Hirobumi
;
Yamaki, Masahiro
;
Teranishi, Yoshiaki
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the pi electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of pi-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the it-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems.