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  • 1990-1994
  • 1985-1989  (5)
  • 1987  (5)
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  • 1990-1994
  • 1985-1989  (5)
Year
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 7118-7124 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reflection symmetry of the spatial part of the electronic wave function for 3Π diatomic molecular states is examined carefully for the individual Λ doublet levels by means of an approach presented earlier [M. H. Alexander and P. J. Dagdigian, J. Chem. Phys. 80, 4325 (1984)]. The results are: For a 3Π molecule in Hund's case (a) the electronic wave function in the Ω=1 (F2) e levels will be antisymmetric and, in the the f levels, symmetric with respect to reflection of the spatial coordinates of the electrons in the plane of rotation of the molecule. The electronic wave functions in the F1 and F3 levels will not have a defined plane of symmetry. By contrast, in the Hund's case (b) high J limit, the electronic wave function in the F1e, F2 f, and F3e levels will be antisymmetric and, in the F1 f, F2e, and F3 f levels, symmetric with respect to reflection. Thus, the symmetry of the wave functions in the F2Λ-doublet levels reverses with the passage from case (a) to case (b). In the case (b) limit, the main branch P and R lines of a 3Π–3Σ− transition will probe antisymmetric levels, irrespective of the Fi level of the 3Π state, while the main branch Q lines will probe symmetric levels. This will be reversed for a 3Π–3Σ+ transition. At low J, in the case (a) limit, in a 3Π–3Σ− transition the P2i and R2i lines with i odd and the Q2i lines with i even will probe antisymmetric levels, while the P2i and R2i lines with i even and the Q2i lines with i odd will probe symmetric levels; the other 18 rotational branches probe levels with no well-defined reflection symmetry.
    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 86 (1987), S. 4790-4800 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The fully quantum theory is developed for 1P→3P transitions in collisions of electronically excited (nsn'p) alkaline earth atoms with closed shell atoms. Spin-changing transitions occur by means of the small spin–orbit mixing between the 1P and 3PJ=1 states of the isolated atom, and are facilitated by the crossing between the 1Π and 3Σ potential curves which correlate, respectively, with the 1P and 3P asymptotes. Close-coupled calculations are carried out for the Ca(4s5p)+He system, based on four different choices of the necessary interaction potentials. Particular attention is devoted to the simulation of the recent experiment of Hale, Hertel, and Leone [Phys. Rev. Lett. 53, 2296 (1984)], in which the 1P→3P cross section was determined in a crossed-beam experiment as a function of the orientation of the initially excited 5p orbital. This polarization dependence depends critically on the long-range splitting between the 1Π and 1Σ curves. A fully adiabatic description of the collision dynamics is used to interpret the results of the quantum scattering calculations. No clear-cut theoretical justification is found for the "orbital following'' models which have been developed to interpret prior experimental studies of collisions involving excited atoms in P electronic states. Rather, a picture emerges in which the initially selected orientation of the Ca p orbital correlates, at short range, with equal probability to Σ-like and Π-like potential curves. Variations in the 1P→3P cross sections are due to long-range Coriolis coupling between the electronic orbital and nuclear orbital momenta and may reflect quantum interference effects between the Π-like and Σ-like adiabatic potentials.
    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 86 (1987), S. 2044-2050 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show how the linear reference potential method for solution of the close-coupled equations, which arise in inelastic scattering theory, can be reformulated in terms of an "imbedding-type'' propagator. Explicit expressions are given for the blocks of the propagator matrix in terms of Airy functions. By representing these functions in terms of moduli and phases, in both classically allowed and classically forbidden regions, one can evaluate the propagator without any numerical difficulty. The resulting algorithm is tested on a highly pathological problem—the rotationally inelastic scattering of a polar molecule by a spherical ion at extremely low kinetic energy—and found to be completely stable.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 4937-4947 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report rotationally inelastic transition probabilities for N2 scattered from a rigid, flat as well as a weakly corrugated Ag surface. For this system Sitz, Kummel, and Zare [J. Vac. Sci. Technol. A 5, 513 (1987)] have recently measured the population state distribution and the quadrupole and hexadecapole alignment of the rotational angular momentum vector with respect to the surface normal. These alignment ratios are directly proportional to the coefficients in a Legendre expansion of the classical angular momentum spatial distribution function. Quantum mechanical expressions for this distribution function in terms of state multipoles of the density operator are presented, and then the classical limit is obtained by introducing asymptotic expressions for the vector coupling coefficients which appear in them. The effect of lattice symmetry on the collisional reorientation of the incident rotational angular momentum vector is investigated through close-coupled scattering calculations based on a model interaction potential. Specular scattering is dominated by ΔM selection rules. The alignment of the rotational angular momentum vectors is analyzed in terms of these selection rules and the azimuthal dependence of the interaction potential.
    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 87 (1987), S. 3218-3231 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Close-coupled calculations of transition probabilities for rotationally inelastic scattering of NO(X 2Π) by a rigid, uncorrugated Ag(111) surface are presented. These calculations explicitly include the two adiabatic potential energy surfaces of V+ and V− symmetry, which are required in a fully quantum mechanical treatment of the collision dynamics. This enables us to provide the first theoretical description of the dependence of the transition probabilities on the spin–orbit and Λ-doublet states of the scattered molecules, which are a direct manifestation of the open-shell character of the 2Π electronic ground state of NO. A comparison is made with the results of experiments by Luntz, Kleyn, and Auerbach at IBM, and Zare and co-workers at Stanford.
    Type of Medium: Electronic Resource
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