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  • 1
    Electronic Resource
    Electronic Resource
    Extraction of ground state properties by discretized path integral formulations (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3233-3239 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We offer a way of determining the temperature range in which a path integral (PI) formulation of the quantum partition function works well and a way of calculating the ground state properties without employing extremely low temperatures (in order to elude the awkward problem that the quantities calculated by the PI formulation become inaccurate with decreasing temperature owing to unavoidable truncation of an infinite number of path integral variables). The fact that the PI energy, specific heat, etc. behave in a low temperature range against physical laws makes it possible to locate the "marginal'' temperature at which the PI specific heat begins to grow infinitely and to estimate the lowest temperature at which the PI formulation functions well (the "threshold temperature''). Whether or not the threshold temperature is low enough to extract only the ground state properties can be answered by either checking if the PI energy and free energy are equal at the threshold temperature or checking if the PI specific heat is relatively small thereat. If the system is in the ground state at the threshold temperature obtained, it is recommended to calculate the ground state properties at this temperature. This scheme can be executed by Monte Carlo methods, being open to many-particle systems. Using the discretized PI formulations, we apply the above procedure to a harmonic oscillator and a double-well potential. It is concluded that this scheme is successful at least as long as the potential is a slowly varying function of coordinates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454980
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  • 2
    Electronic Resource
    Electronic Resource
    Theory of resonance secondary emission in femtosecond laser excitation: On the connection with wave packet dynamics (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5960-5973 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 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).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457414
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  • 3
    Electronic Resource
    Electronic Resource
    Statistical mechanics calculation of the sorption characteristics of argon and nitrogen in dehydrated zeolite 4A by a Monte Carlo method for determining configuration integrals (1987)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 91 (1987), S. 4044-4055 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100299a023
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of quantum beats in time-resolved multiphoton ionization of molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1501-1510 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454128
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum control of nuclear wave packets by locally designed optimal pulses (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9318-9331 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477593
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  • 6
    Electronic Resource
    Electronic Resource
    Monte Carlo calculation of the quantum partition function via path integral formulations (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6390-6398 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using Bennett's Monte Carlo (MC) method, we calculate the quantum partition functions of path integral formulations. First, from numerically exact results for a harmonic oscillator and a double-well potential, we discuss how fast each approximate partition function converges to the exact value as the number of integral variables involved in the formulation is increased. It turns out that most effective and most suitable for the MC simulation is Takahashi and Imada's path integral fomulation based on a modified Trotter formula in which the original potential is replaced with an effective one. This formulation is well balanced between the following two factors: the effect of zero potential energy is underestimated, resulting in an improper increase in the partition function; and, on the other hand, effective potential restricts the motion of fictitious particles born in the formulation so that the partition function value tends to be smaller. Fictitious particles can be treated as classical ones. We therefore can apply Bennett's MC method to calculating the ratio of two quantum partition functions (of a system under consideration and a reference system). As the number of fictitious particles N is increased, choice of reference system becomes less and less important and multistage sampling becomes dispensable. This, to some extent, compensates for the expense that N is larger than the real particle number. The tunneling mechanism of fictitious particles in the simulation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454476
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  • 7
    Electronic Resource
    Electronic Resource
    Resonance Raman overtone intensity calculations of a matrix-isolated I2 molecule by the symmetrized split operator fast Fourier transform method (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1071-1079 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Resonance Raman overtone progressions of I2 in an Ar crystal are computed using the time dependent formula of Raman scattering which has been known to possess distinct computational advantages over the Kramers–Heisenberg–Dirac sum-over-states method, especially when treating condensed phase systems. The symmetrized split operator fast Fourier transform method, which provides a simple and accurate algorithm, is applied to computing the time evolution of the vibrational wave packet involved in the time dependent formula. Our calculated result based on Heller's time dependent formula is in qualitative agreement with the experimental one of Grzybowski and Andrews, but there are some discrepancies between them (for example, the overtone enhancement with the 530.9 nm excitation is not so strong as the experimental one). Those discrepancies are ascribed to the adopted assumption that the line shape for a vibronic transition is a Lorentzian and it is independent of the vibrational level in the excited electronic state. The use of an incident frequency dependent line shape proves to resolve the disagreements to a great extent, which implies that to obtain perfect agreement one needs to explicitly deal with the motion of the trapped molecule and its neighboring host atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450549
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  • 8
    Electronic Resource
    Electronic Resource
    Non-Markoffian theory of quantum beats in molecular fluorescence (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 2112-2119 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a theory of quantum beats in molecular fluorescence taking into account collision effects (such as pure dephasing due to elastic collision) without invoking the Markoff approximation. Model calculations of the time dependent fluorescence from molecules with two excited levels are performed in order to see how the non-Markoffian character in the collision process exerts influence upon the quantum beat pattern. It is suggested that if the pure dephasing between the excited states is a Markoffian "the degree of modulation of the beats'' decreases exponentially with time; if it is in the static limit the degree of modulation of the beats decreases as a Gaussian function (the non-Markoffian behavior in the quantum beats). A given case can be classified as either Markoffian or non-Markoffian, depending on the relative magnitudes of the collision duration time τc, the beat frequency ω, and the coupling strength v which is characteristic of the pure dephasing process. The Markoff approximation holds only if the condition ω〈v〈1/τc is satisfied; the non-Markoffian behavior appears in the quantum beat pattern when ω〉v, even if v2τ2c〈1 .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450422
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of ethanol on free coenzyme A, free carnitine and their fatty acid esters in rat liver
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism 210 (1970), S. 448-455 
    Details
    ISSN: 0005-2760
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2760(70)90041-X
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  • 10
    Electronic Resource
    Electronic Resource
    Theoretical studies of molecules adsorbed on solid surfaces - I. Electronic spectra
    Amsterdam : Elsevier
    Surface Science 134 (1983), S. 614-638 
    Details
    ISSN: 0039-6028
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0039-6028(83)90062-6
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