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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 9095-9104 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The infrared multiphoton photodissociation of a molecular ion, HCl+ in intense (I〉1013 W/cm2), short (τ≤1 ps) laser pulses is studied numerically by solving the nonperturbative time-dependent Schrödinger equation for this system. In particular, since molecular ions have large permanent moments upon dissociation, the present calculation examines the relative importance of electronic and permanent dipole moments effects at high intensities. Both long (λ=20.6 μm) and short (λ=1.064 μm) wavelength are compared to previous experiments and barrier suppression models. It is found in general that at long wavelength electronic effects predominate, thus justifying the use of a static field barrier suppression mechanism to predict the onset of dissociation. High intensity low frequency photodissociation also implies considerable redistribution of ponderomotive energies for light particles such as protons by charge transfer effects. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 1257-1265 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A finite element (FE) method in three-dimensional Cartesian coordinates is described to solve the time dependent Schrödinger equation for H+2, H2, and H+3 in the presence of time dependent electromagnetic fields. The ionization rates and harmonic generation spectra have been calculated for these molecules for field directions parallel or perpendicular to the molecular axis. Nonlinear optical susceptibilities of H+2 have been also obtained for different laser field directions. The time dependent Hartree–Fock results are compared to frozen core calculations for H2. Comparisons of present FE numerical results with previously published calculations show the FE method reproduces perturbative results and can also treat nonperturbatively the effect of intense short laser pulses as the method includes both bound and continuum electronic states. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 340-349 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A coupled equations approach based on a general artificial channel method is used to demonstrate two color laser coherent control of photopredissociation and photoionization in Cl2. Photopredissociation of the 1Πg states of Cl2 is suppressed by a two plus four photon interference process 2ω2=4ω4, whereas the photoionization is controlled by interference between a six photon transition and a four photon transition 6ω4=2ω2+2ω4 using the same 1Πg photopredissociation resonances as intermediates. Photopredissociation angular distributions illustrate the suppression of the corresponding transition in selective rotational states.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    International journal of cosmetic science 13 (1991), S. 0 
    ISSN: 1468-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: α-bisaboloi and d-panthenol are used in many cosmetic preparations, respectively, for their anti-inflammatory and regenerating properties. Their quantitative determination was an important element of their evaluation in these emulsions. Their concentration has been determined by gas chromatographic techniques, using a flame ionization detector. In both cases, the internal standards have been chosen for their compatibility with the analysis of extracted substances.Owing to the complexity of the cosmetic formulations, a preliminary extraction of α-bisabolol and d-panthenol was necessary. For the two substances the preparative separation was based on a liquid–liquid extraction. After dissolving the emulsion in methanol and diluting it with an aqueous buffer solution α-bisabolol was then extracted by ethyl acetate and d-panthenol by ethyl formate.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 6761-6770 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dressed molecular Hamiltonian for molecules in strong electromagnetic fields is derived in the Bloch–Nordsieck (BN) and electric field (EF) representations beyond the dipole approximation. Both representations, which are related by simple unitary transformations generate photon coherent states beyond the dipole approximation. It is shown that applying the dipole approximation to the complete molecule–field equations leaves recoil corrections of order (v/c) which are field dependent. This implies that in the BN representation all Coulomb potentials will be modified at high intensities. In particular, electron–electron repulsions are subject to field dependent photon recoil corrections, which for very intense fields necessitate relativistic corrections as well.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 7224-7231 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The phase corrected adiabatic separation method proposed recently by Marechal [J. Chem. Phys. 83, 247 (1985)] is reexamined. We have been able to show that a state independent differential equation exists, which governs the phase coupling function f of this method, if f further satisfies a set of constraints, Eqs. (7) of the present paper. The method is illustrated by its application to three simple, exactly soluble two-body systems: the free hydrogen atom, the linearly forced hydrogen atom, and the system of two harmonically coupled oscillators. We show that for these systems, the present method, which employs an adiabatic separation procedure, after phase correcting the Hamiltonian, leads to exact results, suggesting its utility for more general problem, involving nonseparable potentials. A nonseparable system of particular interest is the dressed hydrogen atom, which is a representative of all dressed systems, molecular or atomic, with respect to radiative couplings. The method of phase corrected adiabatic separation is shown to give, for field frequencies lying below an IR threshold, a better representation for the exact eigenstates of this dressed systems, as ensuing residual couplings are estimated to be of second order in the original radiative coupling constant.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 2840-2850 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is shown that coupled equations for multiphoton processes can be written with either momentum transition moments or dipole transition moments. In perturbation (low field intensity) theories, nonadiabatic corrections are necessary to make the adiabatic momentum electronic transition probabilities nonzero and equivalent to electronic dipole transition probabilities in infrared transitions. For strong fields, nonadiabatic interactions can become important due to multiphoton resonances, and both approaches necessitate full coupled equations. In the case of electronic excitations, adiabatic, nuclear dipole transition probabilities become nonzero and equivalent to nuclear momentum transitions probabilities only after nonadiabatic corrections are included. These corrections should become important at strong fields for electronic states coupled nonadiabatically. It is shown further using a representation which introduces field modified electronic functions and electronic potentials that unusual field effects will occur at photon frequencies in resonance with adiabatic electronic potential energy separations at pseudo (avoided) crossings. Thus, in such cases, electronic energy gaps are increased by the field and nonadiabatic couplings at these avoided crossings are reduced by the field. Strong resonant fields should therefore quench nonadiabatic couplings at avoided crossings, rendering nonadiabatic reactions more adiabatic.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 5257-5266 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A coupled equations method is used to examine nonadiabatic effects on two- and three-photon transitions in diatomics. Using C12 as a test case, it is shown that nonadiabatic corrections are less important for virtual (nonresonant) transitions than in the case of resonant transitions. The contributions from virtual transitions diminish with the order of the multiphoton transition. Finally, the present method enables one to calculate transition amplitudes. The phase information in such amplitudes are shown to be useful to identify photon pathways in some multiphoton transitions especially at high intensities where the coupled equations approach enable us to go beyond perturbative methods.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4279-4287 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We extend our previous studies on control of dissociation and vibrational excitation of a diatomic molecule using chirped, intense, infrared laser pulses [Phys. Rev. Lett. 65, 2355 (1990)]. The present model includes molecular rotations and a realistic molecular dipole function. The results obtained from numerical integration of the time-dependent Schrödinger equation show a considerable sensitivity of dissociation probabilities to the initial rotational quantum number. Although rotational effects generally decrease the excitation efficiency compared to previous nonrotating molecule results, the dissociation probability induced by chirped pulses is still four to eight orders of magnitudes greater than that for monochromatic pulse dissociation.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1185-1193 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Coherent excitation of molecules with laser pulses are usually described by coupled time-dependent linear parabolic partial differential equations, i.e., Schrödinger equations. Numerical solutions of these equations based on splitting (factorization) of the exponential form of the evolution operator or time-dependent propagator are examined for accuracy of amplitude and phase as a function of various unitary splitting schemes.
    Type of Medium: Electronic Resource
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