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  • 1
    Electronic Resource
    Electronic Resource
    Exact tunneling calculations (1971)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 93 (1971), S. 1840-1851 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00737a002
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic spectroscopy of polyatomic molecules by low-energy, variable-angle electron impact (1979)
    s.l. : American Chemical Society
    Chemical reviews 79 (1979), S. 77-96 
    Details
    ISSN: 1520-6890
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cr60317a006
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  • 3
    Electronic Resource
    Electronic Resource
    Reply to "Comment on: ‘Total scattering, surface ionization, and photoionization of a beam of H3 metastable molecules' '' (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 5985-5986 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454518
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  • 4
    Electronic Resource
    Electronic Resource
    Total scattering, surface ionization, and photoionization of a beam of H3 metastable molecules (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6766-6781 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In a previous paper we reported a technique for generating an intense hyperthermal beam of hydrogen atoms and metastable H3 molecules. From the flight time of the H3 species between the source and detector we estimated that its lifetime exceeds 40 μs and that it must therefore be in the 2 p 2A‘2 excited Rydberg state. In this paper we report experiments utilizing this novel source of H3 molecules. Beam-gas attenuation measurements indicate that the H3–Ar cross section is roughly ten times larger than the H–Ar cross section for translational energies in the 1 to 10 eV range. This observation is consistent with the assignment of the H3 to that excited state, which has a much larger effective radius than a ground state hydrogen atom. The temperature dependence of the surface ionization of H3 by heated tungsten and platinum filaments is used to obtain effective ionizational potentials of this species. These potentials suggest that upon interaction with a metal surface, the metastable state decays to the repulsive 2 p 2E' state which then surface ionizes to produce H+3. The production H+3 and H+ when the H3 beam is irradiated with UV light from a high pressure mercury lamp was also observed and is attributed to the relatively low ionization potential (∼3.7 eV) of the 2 p 2A''2 metastable state of H3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452376
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  • 5
    Electronic Resource
    Electronic Resource
    Design and operation of a stable intense high-temperature arc-discharge source of hydrogen atoms and metastable trihydrogen molecules (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1061-1065 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report a design for a stable intense beam source of hyperthermal hydrogen atoms. The basis for the design is an arc heater used first by Knuth for the generation of high-translational energy He–Ar beams. In the case of hydrogen atom generation this source is very unstable due to the corresponding higher temperatures which are generated by the plasma discharge. We have substantially eliminated these difficulties by the insertion of discharge-localizing insulators and the use of a tungsten nozzle mounted in the center of a 1-kG electromagnet. This source generates exceptionally high hydrogen atom beam intensities of ∼1022 atoms s−1 sr−1 with translational energy distribution functions which extend to 18 eV and whose peak occurs at energies as high as 13 eV. In addition metastable H3 molecules having an intensity between 1020 and 1021 molecules s−1 sr−1 are formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138659
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  • 6
    Electronic Resource
    Electronic Resource
    Accurate first-derivative nonadiabatic couplings for the H3 system (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 4640-4659 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A conical intersection exists between the ground (1 2 A′) and the first-excited (2 2A′) electronic potential energy surfaces (PESs) of the H3 system for C3v geometries. This intersection induces a geometric phase effect, an important factor in accurate quantum mechanical reactive scattering calculations, which at low energies can be performed using the ground PES only, together with appropriate nuclear motion boundary conditions. At higher energies, however, such calculations require the inclusion of both the 1 2A′ and 2 2A′ electronic PESs and the corresponding nuclear derivative couplings. Here we present ab initio first-derivative couplings for these states obtained by analytic gradient techniques and a fit to these results. We also present a fit to the corresponding 1 2A′ and 2 2A′ adiabatic electronic PESs, obtained from the ab initio electronic energies. The first-derivative couplings are compared with their approximate analytical counterparts obtained by Varandas et al. [J. Chem. Phys. 86, 6258 (1987)] using the double many-body expansion method. As expected, the latter are accurate close to conical intersection configurations but not elsewhere. We also present the contour integrals of the ab initio couplings along closed loops around the above-mentioned conical intersection, which contain information about possible interactions between the 2 2A′ and 3 2A′ states. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1390510
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  • 7
    Electronic Resource
    Electronic Resource
    Asymptotic analysis of state-to-state tetraatomic reactions using row-orthonormal hyperspherical coordinates (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 8285-8297 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The state-to-state asymptotic analysis of tetraatomic reactions is presented. It is assumed that the four-atom time-independent partial wave Schrödinger equation has been solved subject to the condition that in the limit of very compact geometries the wave function vanishes. These solutions are initially obtained in body-fixed row-orthonormal hyperspherical coordinates and transformed in the asymptotic arrangement channel regions of nuclear configuration space to Jacobi body-fixed coordinates. From the latter, compact explicit expressions for the reactance (R) and scattering (S) matrices, useful for accurate numerical calculations, are obtained. The different systems of coordinates used and their interrelations are given. The approach described is particularly well suited for implementation on massively parallel architectures and is appropriate for the calculation of benchmark-quality state-to-state integral and differential cross sections on currently available computers. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1408288
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  • 8
    Electronic Resource
    Electronic Resource
    An optimal adiabatic-to-diabatic transformation of the 1 2A′ and 2 2A′ states of H3 (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 1035-1062 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular reaction dynamics in the adiabatic representation is complicated by the existence of conical intersections and the associated geometric phase effect. The first-derivative coupling vector between the corresponding electronically adiabatic states can, in general, be decomposed into longitudinal (removable) and transverse (nonremovable) parts. At intersection geometries, the longitudinal part is singular, whereas the transverse part is not. In a two-electronic-state Born–Huang expansion, an adiabatic-to-diabatic transformation completely eliminates the contribution of the longitudinal part to the nuclear motion Schrödinger equation, leaving however the transverse part contribution. We report here the results of an accurate calculation of this transverse part for the 1 2A′ and 2 2A′ electronic states of H3 obtained by solving a three-dimensional Poisson equation over the entire domain U of internal nuclear configuration space Q of importance to reactive scattering. In addition to requiring a knowledge of the first-derivative coupling vector everywhere in U, the solution depends on an arbitrary choice of boundary conditions. These have been picked so as to minimize the average value over U of the magnitude of the transverse part, resulting in an optimal diabatization angle. The dynamical importance of the transverse term in the diabatic nuclear motion Schrödinger equation is discussed on the basis of its magnitude not only in the vicinity of the conical intersection, but also over all of the energetically accessible regions of the full U domain. We also present and discuss the diabatic potential energy surfaces obtained by this optimal diabatization procedure. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1419257
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  • 9
    Electronic Resource
    Electronic Resource
    Hyperspherical harmonics for tetraatomic systems (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 9184-9208 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A recursion procedure for the analytical generation of hyperspherical harmonics for tetraatomic systems, in terms of row-orthonormal hyperspherical coordinates, is presented. Using this approach and an algebraic Mathematica program, these harmonics were obtained for values of the hyperangular momentum quantum number up to 30 (about 43.8 million of them). Their properties are presented and discussed. Since they are regular at the poles of the tetraatomic kinetic energy operator, are complete, and are not highly oscillatory, they constitute an excellent basis set for performing a partial wave expansion of the wave function of the corresponding Schrödinger equation in the strong interaction region of nuclear configuration space. This basis set is, in addition, numerically very efficient and should permit benchmark-quality calculations of state-to-state differential and integral cross sections for those systems. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412603
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  • 10
    Electronic Resource
    Electronic Resource
    Collinear quasiclassical trajectory study of collision-induced dissociation on a model potential energy surface (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1463-1476 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quasiclassical trajectory calculations have been carried out at energies above the threshold for collision-induced dissociation for a model symmetric collinear atom–diatomic molecule system. Exact quantum mechanical calculations have shown that quasiclassical trajectories give a qualitatively correct picture of the dynamics in this system, in so far as reaction and total dissociation probabilities are concerned. Trajectories leading to dissociation are found to lie almost entirely in well-defined reactivity bands, with the exception of a few occurring in a small chattering region in which the outcome of the trajectory is extremely sensitive to its initial conditions. The energy distribution functions of the dissociated atoms are obtained and shown to vary substantially with initial conditions (reagent vibrational and translation energy). The form of these distributions is, to a major extent, determined by the position and width of the reactivity bands. The different dissociation reactivity bands are shown to be associated with different types of trajectories. Part of the vibrational enhancement of dissociation arises from the fact that the simplest possible trajectory leading to dissociation (one which crosses the symmetric stretch line only once prior to the onset of dissociation) is not obtained with ground state reagents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450491
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