Search Results - (Author, Cooperation:Y. Fujimura)

2018-06-07

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

2013-11-15

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Acetylation/drug effects ; Adoptive Transfer ; Animals ; Butyrates/analysis/*metabolism/pharmacology ; *Cell Differentiation/drug effects ; Colitis/drug therapy/pathology ; Colon/cytology/*immunology/metabolism/*microbiology ; Conserved Sequence ; Female ; *Fermentation ; Forkhead Transcription Factors/genetics ; Germ-Free Life ; Histones/metabolism ; Homeostasis/drug effects ; Intestinal Mucosa/cytology/immunology ; Lymphocyte Count ; Magnetic Resonance Spectroscopy ; Male ; Metabolome ; Mice ; Promoter Regions, Genetic/drug effects ; *Symbiosis ; T-Lymphocytes, Regulatory/*cytology/drug effects/immunology

2018-02-07

Wiley-Blackwell

0007-0963

1365-2133

Medicine

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Renormalization effects of the bath-induced vibronic population transfer on resonant light scattering (RLS) from molecules in condensed phases are theoretically studied based on the Markoffian master equation approach. By using the double space diagram technique, the self-energy originated from the bath-induced vibronic population transfer is analytically solved, and the analytic expressions for the intensities both of the stationary and of the time-resolved RLS spectra are derived. The renormalization effect is analyzed in terms of dimensionless molecular parameters, and model calculations are also performed to confirm theoretical results.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The Fourier-expansion density matrix method is developed to describe the multiphoton processes of molecules interacting with the heat bath under the strong laser light. This method is applied to deriving expressions for the absorption spectra in the case in which a single-mode laser interacts with the molecular system of a three-level taking into account the dynamic Stark effect. Model calculations are performed to demonstrate the dynamic Stark effects on the absorption ability in the three-level system, and compared with the results of the weak laser light case. The calculated band shapes of the two-photon absorption are analyzed in terms of the simultaneous and sequential mechanisms. The sequential mechanism is characterized by bath-induced intramolecular transitions. As the laser intensity is increased the simultaneous mechanism makes a dominant contribution with increased dynamic Stark effects.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The resonance secondary emission (RSE) in femtosecond laser excitation is discussed in reference to the motion of the created wave packet moving on the excited state potential surface. The density matrix of emitted light for the multi-intermediate-level system is outlined, from which the emission correlation function is derived. The correlation function is put into the theoretical expression of the time-dependent "physical spectrum'' for the Fabry–Perot interferometer (which is used in order to consider temporal and energetic resolution inherent in detection). The compact and practical expressions obtained connect the time- and frequency-resolved spectrum with the time evolution of the wave packet. Numerical results for a displaced harmonic oscillator model indicate that the time- and frequency-resolved spectrum can reveal how the wave packet created by a fs laser pulse travels on the excited potential surface if the response time 1/Γd of the photodetector satisfies the relation that Ω〈Γd 〈∼ the Stokes shift (where Ω is the vibrational frequency). It is shown that the excited state wave function can be split into two terms, the one that adiabatically follows the temporal change in incident light (the adiabatic term) and the one that represents the effect of spectral broadening of light (the Fourier broadening term). It is only the Fourier broadening term that survives after the termination of incident light and reflects the motion of the created wave packet on the excited potential surface. In off-resonance excitation, the adiabatic term produces Raman-like emission and the Fourier broadening one produces fluorescence-like emission. In resonance excitation, these two terms are indistinguishable from each other with respect to emission frequency: for the duration of incident light, the adiabatic term offsets the Fourier broadening one, leading to a slow buildup of intensity in the time- and frequency-resolved spectrum (which is slower than the initial rise of the incident pulse profile).

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Effects of the coherence transfer induced by the molecule–heat bath interactions on the ultrashort time-resolved coherent anti-Stokes Raman scattering (CARS) from molecules in liquids are theoretically studied. Based on the perturbative density matrix formalism an expression for the CARS intensity is derived taking into account the coherence transfer between the Raman active vibrational transitions of two molecules in liquids. The coherence transfer constants and dephasing constants are properly incorporated with the aid of Liouville space Feynman diagrams. The structure of the coherence transfer matrix element which expresses the time evolution of the coherence between the relevant transitions is clarified by solving the Master equation with the coherence transfer and dephasing constants in the Markoff approximation. Frequency shifts of the quantum beats appear in the time-resolved CARS as a result of the coherence transfer. A multispherical layer model is adopted in evaluating the coherence transfer effects in liquids in femtosecond time domains. Model calculations of time-resolved CARS spectra have been carried out to demonstrate the coherence transfer effects in both short and long range coherence transfer cases. It is predicted that the quantum beats are amplified in the time-resolved CARS spectra of molecules in liquids in a long range coherence transfer case when there exist differences in the coherence transfer constants between each spherical layer.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

A theory of the emission spectrum from a multilevel molecular system pumped by strong resonant radiation fields based on the double space theory of the density matrix is developed. We are especially concerned with a three-level, one-laser system, and a three-level, two-laser system. It is shown that the band structure cannot always be estimated by the energy level structure of the dressed states. In fact, in both model systems, triplet structures of the emission spectra can be observed in the case where the magnitude of the molecule-field interaction is larger than that of the detuning. The characteristic features of the band structure are interpreted in terms of the dressed state picture based on analytically solvable models. Several numerical calculations are performed to show how the multiplet band structure in the emission spectrum is influenced by the detuning and the power of the pump field(s).

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Effects of vibronic coherence transfer induced by the heat bath on ultrafast time-resolved resonant light scattering (RLS) spectra are theoretically investigated within the master equation approach. The vibronic coherence initially created by a coherent optical excitation transfers to other vibronic coherent states due to inelastic interactions between the vibronic system concerned (the relevant system) and the heat bath. The vibronic coherence transfer results in the quantum beats in the time-resolved RLS spectra. The bath-induced vibronic transition operator is derived in the double space representation of the density matrix theory. Model calculations of the femtosecond (fs) time-resolved RLS spectra are performed to demonstrate the effects of the bath-induced vibronic coherence transfer.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

In order to obtain semiconductivity, rutile crystals have been doped with Nb by means of diffusion. The resulting Nb-doped rutile crystals have an electrical resistivity (approximately-equal-to)80 Ω cm at room temperature. Impedance analysis of a Nb-doped TiO2-Au diode suggests that the measurement frequency must be lower than 10 kHz to detect the capacitance and conductance of the depletion layer. Thus, an admittance spectroscopic method is used to study traps in the diode of the Nb-doped TiO2-Au. Two trap levels, located at 0.24 and 0.37 eV below the bottom of the conduction band, have been detected by this method. The state densities and capture cross sections of these trap levels are also determined.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Bath-induced coherence transfer effects on a time- and frequency-resolved resonant light scattering spectrum is theoretically investigated using the Markoff master equation. According to Eberly and Wódkiewicz, a general expression for an experimentally observable spectrum in terms of a molecular response function is derived within the density matrix formalism. To generalize our previous results of the bath-induced coherence transfer which were derived based on a displaced harmonic oscillator model [Y. Ohtsuki and Y. Fujimura, J. Chem. Phys. 91, 3903 (1989)], an eigenstate basis is used to represent a relevant system for investigating characteristics of the transfer. By the present model, we clarify the dependence of the bath-induced coherence transfer on the energy-level structure of the intermediate states associated with the transfer, i.e., energy mismatch effects. It is shown that if the energy mismatch of these states is smaller than dephasing rates, the bath-induced coherence transfer occurs resonantly. In the other cases, the energy mismatch brings about a modulation in the time evolution of the superposition state created by the bath-induced coherence transfer, which strongly diminishes the efficiency of the transfer. The resonance condition is derived analytically and is confirmed by numerical calculations of quantum beats induced by the bath-induced coherence transfer. The possibility of very rapid dephasing of a quantum beat signal which cannot be explained in terms of dephasing rates is also shown, when the transition moments have such values that give π-phase-shifted quantum beats in bath-induced fluorescence. © 1996 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We present a theory for controlling the dynamics of a dissipative, quantum system with a laser field optimized locally in time. The theory is applicable to both weak and strong field control of the quantum dynamics. The theoretical groundwork is based on the equation of motion of the density matrix in Liouville space. Interactions between the molecules and the heat bath are taken into account within a Markov approximation. The derivation of the locally optimized laser field in a feedback form is based on the local optimization theory in the Hilbert space, proposed in a previous paper [M. Sugawara and Y. Fujimura, J. Chem. Phys. 100, 5646 (1994)]. The theory is applied to a simple, two-level quantum system with a dephasing constant. We present both the calculated time evolution of the off-diagonal density matrix element and that of the population of the states in the optimized laser field. These calculations show that the control of the system by the laser field is sufficient to avoid the dephasing effects. We discuss how the dephasing dynamics affects the optimization of the laser field.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We presented a theoretical method for controlling quantum dynamics by locally optimized nonstationary laser fields, within the semiclassical theory of the molecule–radiation field interaction. The external laser field is optimized based on the control theory of a linear time-invariant (LTI) system, so that both the summation of the population of the nontarget states and the total energies of the laser fields are minimized. The optimization procedure involves operation of the so-called feedback gain matrix to the time-dependent state vector. This procedure is carried out at every successive short stage, in which the time-dependent Schrödinger equation can be approximated to the equation of motion of the LTI system. As an example, the control theory was applied to laser-induced ring-puckering isomerization, the dynamics of which can be described as the wave packet in the one-dimensional double minimum potential under locally optimized laser fields. The result indicated that nearly 100% of the population can be transferred to the final product state by irradiation of the optimized laser fields. The optimized laser fields were analyzed to obtain information on the carrier frequencies or the frequency modulation by using the fast Fourier transform method. These results were then compared with the result of isomerization induced by nonoptimized laser fields.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Laser-induced vibrational predesorption of molecules physisorbed on insulating substrates is theoretically investigated based on the Markoff master equation. The system vibrations, which consist of intramolecular vibrations of an admolecule and admolecule-surface vibrations, are divided by the adiabatic approximation, whereby the predesorption is represented by the nonadiabatic transitions from the bound states to the desorption continuum. By using the projection operator in the double(Liouville)-space representation, the bound-continuum couplings due to the nonadiabatic and the optical interactions are explicitly included in the master equation. The adiabatic theory is applied to CO physisorbed on a NaCl(100) surface, in which CO stretching and CO-surface vibration are chosen as the system vibrations. This two-dimensional model with a shallow Morse potential for the CO-surface potential gives a desorption rate of ∼10−4 s−1, which agrees with the experimentally measured rate by Chang and Ewing [Chem. Phys. 139, 55 (1989) and Phys. Rev. Lett. 65, 2125 (1990)]. The rate equations explicitly derived from the master equation are used to analyze the desorption dynamics. It is shown that predesorption is considerably enhanced by the incoherent phonon-assisted predesorption mechanism, i.e., by thermal excitation of the CO-surface stretching in the manifold of the excited CO stretching. Excitation by a single laser is extended to the two-laser excitation scheme to accelerate the predesorption. © 1997 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Isomerization of HCN is studied numerically for a laser excitation configuration of two perpendicular intense IR pulses. This scheme confines the molecule to a plane and promotes proton transfer along the curved reaction path. It is shown that internal rotation of the CN group enhances isomerization when compared to a fixed C≡N orientation model. Isomerization rates with rotation exceed those without rotation of the CN by about a factor of 3. Internal rotation also enhances dissociation and destroys phase control of the isomerization. It is found that at intensities I∼1013 W/cm2, maximum isomerization occurs with negligible dissociation for a 2 ps pulse excitation. Maximum isomerization is also found for one field frequency resonant with the CH bend frequency ωbend and the other perpendicular frequency at 2ωbend. © 1996 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

An expression for the probability of time-resolved three-photon ionization via coherently excited resonant states of a molecular system is derived in the perturbative density matrix formalism with the aid of the Liouville space Feynman diagram. It is shown how the time evolution of the molecular coherence in the first resonant state can be detected as a function of the delay time between the pumping and probing lasers through the probing two-photon ionization process. The three-photon ionization process consists of the simultaneous and sequential processes which are classified by the Liouville space Feynman diagrams. The possibility of appearance of quantum beats in the pump–probe three-photon ionization is discussed by performing model calculations of the probability of ionization. The role of the direct and redistributed processes is discussed. The redistributed process is induced by intramolecular processes in the resonant state. The theoretical treatment is applied to the (1+2) three-photon ionization of pyrazine observed by Knee et al. It is demonstrated that the fast decay component (110 ps) of the pyrazine spectra originates from the intramolecular dephasing of the vibronic coherence created by the pumping pulse laser, and this component appears only when the redistributed process (the ionization process through triplet levels) is absent.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

A new approach to locally design a control pulse is proposed. This locally optimized control pulse is explicitly derived, starting with optimal control formalism, and satisfies the necessary condition for a solution to the optimal control problem. Our method requires a known function, g(t), a priori, which gives one of the possible paths within the functional space of the objective functional. A special choice of g(t)≡0 reduces the expression of the control pulse to that derived by Kosloff et al. For numerical application, we restrict ourselves to this special case; however, by combining an appropriate choice of the target operator together with the backward time-propagation technique, we apply the local control method to population inversion and to wave packet shaping. As an illustrative example, we adopt a two-electronic-surface model with displaced harmonic potentials and that with displaced Morse potentials. It is shown that our scheme successfully controls the wave packet dynamics and that it can be a convenient alternative to the optimal control method for wave packet shaping. © 1998 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The theory of indirect dephasing proposed by Hiroike is applied to studying the mechanism of line broadening in resonance and dispersed fluorescence spectra of molecular complexes in supersonic free jet. In the indirect dephasing model, the width of the luorescence spectra which is characterized by the homogeneous linewidth can be expressed in terms of two parameters, the rate of intramolecular vibrational redistribution (IVR), γ and frequency change induced by the IVR, δω. It is shown that the non-Markovian character introduced into the interaction between the intra- and intermolecular modes reduces the indirect dephasing rate. The theory is applied to calculation of the linewidth of the resonance fluorescence of the tetrazine–Ar molecular complex excited in 6a1 vibronic level. The introduction of the non-Markovian character is necessary to calculate the linewidth of the fluorescence in a molecular complex with a few intermolecular modes such as tetrazine–Ar.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Effects of vibration–rotation (Coriolis) couplings on the coherent polarization anisotropy are theoretically studied in a time-resolved two-photon ionization of a symmetric top molecule. This polarization anisotropy originates from a coherent excitation of the resonant rovibronic molecular eigenstates (rovibronic coherence) whose zeroth order states are mixed through the Coriolis coupling. Expressions for the time-dependent degree of polarization after the coherent excitation of the rovibronic states produced by the Coriolis coupling are derived as a function of the delay time in the pump–probe two-photon ionization. Model calculations of the time-dependent degree of polarization as well as the probabilities of the two-photon ionization are performed to demonstrate the Coriolis coupling effects in the low excess energy regions of the resonant intermediate state. It is shown that oscillatory behaviors in the time-dependent degree of polarization should be observed as a result of the creation of the rovibronic coherence. It is demonstrated that oscillations of the degree of polarization involve both contribution of the purely rotational J-coherence and that of the rovibronic coherence in the resonant manifold when the rotational branches are coherently excited and the characteristic rotation–vibration interaction energy is larger than a typical free rotational energy under jet-cooled condition.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Expressions for the differential cross section of the resonance Raman scattering from molecules in which initially prepared nonequilibrium vibronic levels undergo vibrational and/or electronic relaxations are derived by using the generating function method. Two kinds of the initial nonequilibrium vibronic distributions, single vibronic level and Poisson ones are taken into account. A displaced harmonic oscillator model for the initial and resonant vibrational states and a linear vibrational quantum number dependence of the relaxation constants are adopted in deriving the cross sections. Model calculations of the time-resolved resonance Raman scattering cross sections and of the excitation profiles of the nth order Stokes and anti-Stokes Raman bands are performed by using the derived expressions. The results of the calculation indicate that the anti-Stokes Raman bands make a significant contribution to the resonance Raman scattering from the nonequilibrium vibronic distributions. It is suggested that measurements of the excitation profiles are useful for analyzing the nonequilibrium distribution initially prepared and the subsequent relaxation mechanism.

Electronic Resource