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  • 1
    Electronic Resource
    Electronic Resource
    Dipole properties, dispersion energy coefficients, and integrated oscillator strengths for SF6 (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 70-77 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Dipole oscillator strength distributions (DOSDs) have been constructed for ground SF6 including the IR, UV, and higher energy parts of the absorption spectrum. An adopted DOSD is used to evaluate the dipole oscillator strength sums Sk, k=2,1, 1/2 (− 1/2 )−3,−4,−6,..., mean excitation energies Ik, k=2(−1)−2, dipole–dipole dispersion energies for the interaction of SF6 with itself and with Li, N, O, H2, N2, O2, NO, H2O, NH3, CO2, CO, H, He, Ne Ar, Kr, and Xe, and the triple–dipole dispersion energy for (SF6)3. Pseudo-DOSDs have been constructed for SF6 which facilitate the evaluation of the dispersion energies involving SF6. In most cases uncertainties in our results for the dipole properties and dispersion energy coefficients are (approximately-less-than)1–3%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449794
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  • 2
    Electronic Resource
    Electronic Resource
    On the control of the production of hydrogen atom 2s–2p resonance hybrids through the use of competitive one- and two-photon transitions from the ground state (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 1501-1507 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The control of the formation of dipolar hydrogen atom 2s–2p hybrid states, through varying the relative phase δ of two lasers inducing simultaneous one- and two-photon transitions from the ground state, is discussed by using time-dependent perturbation theory. Numerical examples are presented that illustrate how the populations of the hybrid states can be controlled by varying δ. The perturbative calculations are augmented by various exact finite basis set, and full split operator/fast Fourier transform, solutions to the time-dependent wave equation for the problem. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481936
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  • 3
    Electronic Resource
    Electronic Resource
    Exchange–Coulomb model potential energy surface for the N2–Ar interaction (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 8477-8491 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An exchange–Coulomb model potential energy surface has been developed for the N2–Ar interaction. This potential energy surface is based upon recent results for the Heitler–London interaction energy, long-range dispersion energies, the temperature dependencies of interaction second virial, binary diffusion, and mixture shear viscosity coefficients, microwave spectra of the van der Waals complex, and collision broadening of the depolarized Rayleigh light scattering spectrum. The adjustable parameters in the final potential surface have been determined by fitting the temperature dependence of the virial coefficient (within experimental uncertainties) and the frequencies of three representative lines of the microwave spectrum of the 14N2–Ar van der Waals complex. A fine tuning of these parameters was achieved by considering the temperature dependence of the binary diffusion and mixture shear viscosity coefficients. Calculated frequencies for all observed microwave transitions of the various N2–Ar isotopomers lie within 0.1% of the experimental values. Excellent agreement is obtained with experimental values of binary diffusion and mixture shear viscosity data for all temperatures and compositions. Agreement with the bulk gas relaxation phenomena, while not outstanding, is acceptable, given the accuracy with which these phenomena are currently determinable. Detailed comparisons are made with predictions of the two best literature N2–Ar potential energy surfaces. This new potential surface gives the best overall agreement with experiment for N2–Ar mixtures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470158
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  • 4
    Electronic Resource
    Electronic Resource
    Perturbation treatment of pump–probe laser–molecule interactions: An application to the fluorescence from the S1 state of α-NPO (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 121-135 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-dependent perturbation theory, together with a (minimal) molecular model consisting of three energy levels (S0,S1,S3), is used to investigate the spectroscopy and the dynamics of fast time resolved, two-photon, two-color, pump–probe experiments, involving the direct S0→S1 two-photon excitation of α-NPO. In particular the theory is used to examine the aitch-theta-dependence of the fluorescence signal from the S1 state, where aitch-theta is the angle between the polarization vectors of the pump and probe lasers, for fixed (zero) time delay between the laser pulses. It is predicted, in contradistinction to the cos2 aitch-theta dependence of the fluorescence signal from the S2 state of azulene arising from the sequential two-photon S0→S1→S2 transition, that the signal from the S1 state of α-NPO can vary between pure cos2 aitch-theta and pure cos4 aitch-theta dependencies and that secondary maxima in the signal, as a function of aitch-theta, can occur for certain laser intensities. Also reported is a new series of experiments for α-NPO, motivated by the theory, that yields results for the fluorescence intensity of the S1 state, as a function of aitch-theta and laser intensity, in agreement with the theoretical predictions. Comparison of experiment and theory is used to estimate the relative orientations of the relevant transition and permanent dipole moments, and the transition moment between the S1 and S3 states of α-NPO. The important role played by the permanent dipoles of the S0 and S1 states, and the importance of including averages over the relative laser phase, the jitter in the time-delay, and the orientations of the absorbing molecules, is emphasized in the theoretical analysis of the problem. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469650
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  • 5
    Electronic Resource
    Electronic Resource
    Perturbative treatments of pump–probe laser-molecule interactions with applications to azulene and trimethylazulene (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4165-4170 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Semianalytic perturbative approaches for investigating the spectroscopy, and the underlying dynamics, associated with fast time-resolved, two-photon, two-color, pump–probe, low intensity laser-molecule interactions are developed and discussed. In particular the perturbation theory is developed with emphasis on molecular models associated with pump–probe experiments on the S0→S1→S2 two-photon transitions in azulene and trimethylazulene. The experiments are discussed and the theory is used to determine the lifetimes of the intermediate S1 states by analyzing the experimental two-photon fluorescence signals from the S2 states as a function of the time-delay between the pump and probe lasers. The advantages of using this approach relative to the traditional methods for determining the lifetime of the S1 states are discussed. The dependence of the two-photon fluorescence signals on the angle between the polarization vectors of the pump and probe lasers, for fixed time delay between the lasers, is also considered briefly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466300
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  • 6
    Electronic Resource
    Electronic Resource
    Two-color multiphoton transitions in molecular beam electric resonance studies: Rotating wave versus Floquet, and on- versus off-resonance, calculations (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 8312-8320 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A nonzero difference, d, between the diagonal dipole moment matrix elements, μjj, of two molecular states involved in either one- or two-color multiphoton transitions, can have substantial impact on the temporal evolution and spectral behavior of the states. The effects of d≠0 are investigated in this paper for two-color transitions in a two-level system previously studied in one-color molecular beam electric resonance (MBER) experiments on symmetric top molecules. The calculations suggest a two-color analog to the one-field experiments, where the flexibility furnished by the field parameters of the two continuous wave electric fields, including relative phase, can be used to advantage. Both exact Floquet calculations and the rotating wave approximation (RWA) are used in this study. Analytic RWA expressions for the one- and two-color molecule-laser(s) couplings are particularly useful in helping to interpret and/or predict the effects of d≠0. The novel aspects of two-color laser-molecule interactions, relative to the one-field case, are emphasized. In addition to investigations related to MBER studies, this work contributes to the more formal aspects of two-color laser-molecule interactions. It is shown that very useful analytical two-level RWA solutions for the on-resonance temporal behavior of the molecular states are available, even in the presence of competing resonances, whereas off-resonance numerically useful analytical results are available only when one multiphoton resonance dominates a transition. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471583
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  • 7
    Electronic Resource
    Electronic Resource
    Reliable anisotropic dipole properties, and dispersion energy coefficients, for O2 evaluated using constrained dipole oscillator strength techniques (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 4927-4937 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Constrained anisotropic dipole oscillator strength techniques are used to obtain reliable values for a wide range of anisotropic and isotropic dipole properties of O2, including the dipole–dipole dispersion energy coefficients for the interaction of O2 with O2, H2, N2, CO, He, Ne, Ar, Kr, and Xe. Some of the anisotropic constraints required for our calculations are obtained via dipole sum rules from ab initio, multireference configuration interaction (CI) wave functions for the ground state of O2. The individual dipole properties of O2 considered include the dipole oscillator strength sums Sk, k=2,1,0(−1/2)−2,−3,−4,..., the logarithmic dipole sums Lk and mean excitation energies Ik, k=2(−1)−2, and, as a function of wavelength, the dynamic polarizability and its anisotropy, the total depolarization ratio, the Rayleigh scattering cross section, and the Verdet constant. Our constrained dipole oscillator strength results are often the only reliable, and sometimes the only available, ones for many of the properties and dispersion energies considered. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472344
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  • 8
    Electronic Resource
    Electronic Resource
    On the effects of absolute laser phase on the interaction of a pulsed laser with polar versus nonpolar molecules (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9351-9365 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The absolute laser phase dependence of the time-dependent populations of the molecular states, including the steady-state (long time) populations of the states, associated with the interaction of a molecule with a pulsed laser is investigated using illustrative two-level examples. One-photon transitions, including the effects of permanent dipoles, are discussed as a function of the pulse duration, intensity, and (absolute) laser phase, for selected laser frequencies. The effects of laser phase can be large, depending on the values of the pulse duration for a given frequency and intensity. The effects of permanent dipoles, relative to no permanent dipoles, are significant for large laser field strengths ε0. When the laser-molecule coupling parameter b=μ12ε0/E21≥0.2, where μ12 and E21 are the transition dipole and energy difference between the ground and excited states, respectively, the dynamics of the pulse-molecule interaction are (strongly) phase dependent, independent of pulse duration, whereas the corresponding steady-state populations of the molecular states may or may not be phase-dependent depending on the pulse duration. Analytical rotating wave approximations for pulsed laser-molecule interactions are useful for interpreting the dynamics and the steady-state results as a function of field strength and pulse duration, including the effects of permanent dipole moments. The results reported in this paper are based on molecular parameters associated with an S0→S1 electronic transition in a dipolar molecule. However, they are presented in reduced form and therefore can be scaled to other regions of the electromagnetic spectrum. Short, intense pulses at or beyond the limits of current laser technology will often be required for the types of absolute laser phase effects of this paper to be appreciable for electronic excitations. The discussion, in the UV-VIS, also suffers from the use of a two-level model and from the requirement of field intensities that can be beyond the Keldysh limit. For other spectral regions, these absolute laser phase effects will be much more readily applicable. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477596
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  • 9
    Electronic Resource
    Electronic Resource
    A reliable new potential energy surface for H2–Ar (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2639-2653 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A reliable new three-dimensional potential energy surface is obtained for the H2–Ar system using an exchange-coulomb potential model with five parameters determined empirically from a least-squares fit to experimental data. This surface fully accounts for new high resolution IR data, virial coefficients, and vibrational transition pressure-shifting coefficients used in the analysis, and yields excellent predictions of elastic and inelastic scattering cross sections and hyperfine transition intensities not included in the analysis. Quantitative comparisons with the best previous empirical potential and a high quality fully ab initio potential are also presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472127
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  • 10
    Electronic Resource
    Electronic Resource
    Ab initio evaluation of multipole dispersion energies and properties (1982)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 86 (1982), S. 1222-1231 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100396a033
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