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  • 1
    Electronic Resource
    Electronic Resource
    Variational calculation of the rovibrational spectrum of H2O using the coupled-rotor basis (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5917-5926 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present rovibrational energies and transition intensities for H2O calculated at several levels of approximation, beginning with the adiabatic approximation (separating slow bending and rotation from fast stretching modes), then coupling the slow modes with the symmetric stretch, and culminating with the inclusion of all the couplings in the Hamiltonian. Evaluation of each approximation is made by comparing the results of the ab initio spectra to experiment. A space-fixed rovibrational basis set is used for the variational calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460452
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  • 2
    Electronic Resource
    Electronic Resource
    Vibrational predissociation of He–I2*(v)–Ne: An approximate quantal study (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2684-2691 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational predissociation (VP) of the He–I2(B 3Π0+u,v)–Ne complex is studied in the range of initial vibrational excitations 25≤v≤35. The rare gas atoms are restricted to move on a perpendicular plane to the I2 axis. A simple addition of pairwise Morse atom–atom interactions is used to describe the potential energy surface. The breaking up of the I2–Ne bond is found to be the dominant dissociation channel for v≤29. However, due to the anharmonicity of the I2 stretch, the situation for v〉29 is just the opposite and the He atom escapes first.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455966
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  • 3
    Electronic Resource
    Electronic Resource
    Coherence effects between intramolecular vibrational relaxation and dissociation in triatomic van der Waals systems (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 1035-1049 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Time-independent [Halberstadt and co-workers, J. Chem. Phys. 96, 2404 (1992); 97, 341 (1992)] and time-dependent quantum mechanical calculations that describe the intramolecular vibrational relaxation (IVR) of Ar...Cl2 are used to develop analytical models for this process. It is shown that time-resolved experiments should reveal an oscillatory dissociation rate. It is found that the oscillations will be different for different rotational levels, and may tend to wash out if insufficient state selection is achieved in the initial excitation step. This may explain why no such oscillations were observed for Ar...I2. It is also predicted that the observed product state rotational distribution will change with the initially excited rotational state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465403
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  • 4
    Electronic Resource
    Electronic Resource
    Energy levels and structure of tetra-atomic van der Waals clusters (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 2217-2230 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A variational treatment is presented to study bound and quasibound states of X1...BC...X2 van der Waals clusters, where X1 and X2 are rare gas atoms and BC is a conventional diatomic molecule. The Hamiltonian operator, including all the degrees of freedom, is expressed in terms of the B–C relative vector and bond coordinates which describe the position of each rare gas atom with respect to the BC center of mass. In a body-fixed reference system, with the Z axis parallel to the diatomic axis, all the matrix elements of the Hamiltonian are evaluated in a basis set of functions which takes into account the symmetries of the system. Numerical applications to the He2...Cl2 and Ne2...I2 complexes are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467662
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  • 5
    Electronic Resource
    Electronic Resource
    Vector Correlations in the Photopredissociation of van der Waals Molecules (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 3307-3316 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100064a011
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  • 6
    Electronic Resource
    Electronic Resource
    Vibrational predissociation dynamics of the He79Br2 van der Waals molecule: A quantum mechanical study (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7454-7463 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The vibrational predissociation of the HeBr2 van der Waals complex is studied by means of both accurate and approximate three dimensional quantum mechanical calculations. Simple atom–atom potentials have been tested for matching experimental measurements at low Br2 vibrational excitations. The fragmentation dynamics when the bromine subunit is close to its B state dissociation limit is then explored and compared with experiments. For low to intermediate vibrational states v, good agreement with most of the data (spectral shifts, lifetimes, average structures, average product energies) is achieved. The closing of the Δv=−1 channel at v=44 and the binding energy at that position are successfully reproduced, although calculated and experimental blueshifts and linewidths are not in such good accordance in the v(approximately-greater-than)38 range. For these high v excitations, fragmentation cross sections exhibit complicated structures indicating strong interactions among different quasibound states. In addition, interesting threshold and intramolecular energy redistribution effects are predicted. The closing of the Δv=−1 channel is found to be a gradual process where different dynamical regimes can be investigated in detail. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472573
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical simulations of the He79Br2 B, v=8←X, v″=0 excitation spectrum: Spectroscopic manifestation of a linear isomer? (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 4620-4628 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Possible manifestations of a linear isomer of a rare gas–halogen molecule van der Waals complex in its B←X excitation spectrum are analyzed using a continuous one-parametric family of X-state potential energy surfaces (PESs) with variable depths of minima in the T-shaped and linear configurations. For the HeBr2 complex as an example, the propensities in the frequencies and intensities of the representative transitions from T-shaped and linear isomers are analyzed and the variation of the whole spectrum with the topology of the X-state PES is established. Qualitatively good agreement with the experimental HeBr2 spectrum clearly suggests that the unassigned secondary band of the observed spectrum is likely formed by transitions from the linear isomer, whose energy is very close to that of the T-shaped one. Present results provide strong evidence for the possibility to detect a linear isomer of rare gas–halogen molecule complexes via conventional excitation spectroscopy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288793
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  • 8
    Electronic Resource
    Electronic Resource
    Strongly mixed resonances in the photofragmentation of HeBr2 near Br2(B) dissociation: Stabilization and close-coupling studies (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 3216-3226 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photofragmentation of the He79Br2 van der Waals complex is studied for the transition from the ground to the excited electronic state B and where the Br2 subunit is also excited to the neighborhood of the v0=45 vibrational state. At this vibrational level the bromine molecule is close to its dissociation limit and the Δv=−1 channel is closed for dissociation of the complex. In a previous work it was suggested that energy in the HeBr2(B, v0=45) quasibound state may be internally redistributed (exciting van der Waals modes at the expense of the bromine excitation) prior to dissociation. Such mechanisms are more deeply studied in this work by means of the stabilization method, which works with square-integrable wave functions and is an appropriate approach to perform quasibound state analysis. Stabilization total cross sections compare fairly well with close-coupling ones, where the proper asymptotic behaviour of the continuum wave functions is taken into account. By inspection of the quasibound state wave functions, it is seen that energy is redistributed to several excited states belonging to the v0−1 manifold. In addition, it is shown that such excited states also carry oscillator strength in the transition from the ground electronic state and thus interference effects in the excitation process are significant. HeBr2 near the halogen dissociation limit is found to be a rather strongly coupled system where the quasibound states involved can only approximately be assigned to quantum numbers corresponding to interhalogen and van der Waals vibrational excitations. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473421
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  • 9
    Electronic Resource
    Electronic Resource
    Potential energy surface and spectroscopy of clusters of rare-gas atoms with cyclopropane (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9288-9299 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Analytical empirical potential energy surfaces describing the van der Waals interaction between rare-gas atoms and cyclopropane are presented. The functional form is based on pairwise Lennard-Jones-type potentials which have been widely used to describe rare-gas-benzene complexes, also studied in this work in order to check our theoretical method and for comparison. The parameters have been chosen in order to accurately fit the high resolution microwave spectra recently reported by Xu and Jäger [J. Chem. Phys. 106, 7968 (1997)]. The observed splitting in the microwave spectra of Ne-cyclopropane, associated with rotational tunneling, is well reproduced. Moreover, such tunneling is also important for complexes of Ar and Kr in excited van der Waals states. These phenomena involve a high delocalization of the wave functions and, therefore, intermolecular spectroscopy techniques would provide a good check of the potential energy surface over a broad region of the configuration space. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477590
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  • 10
    Electronic Resource
    Electronic Resource
    Photodissociation of NeBr2(B) below and above the dissociation limit of Br2(B) (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2566-2575 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation dynamics of the NeBr2 complex in the B electronic state is studied, for the first time, near the Br2(B) dissociation limit, below and above, when the complex is promoted from the ground T-shaped level in the X electronic state. A time-dependent treatment is used in which the initial wave packet is divided in two portions, one describing the slow predissociation dynamics below the Br2 dissociation threshold, and the second one, the fast complete dissociation in Ne+Br+Br fragments. Below that threshold, the absorption spectrum shows an increasing congestion as the vibrational energy content of Br2 increases, but narrow peaks appear again for the highest energy region of the spectrum. These peaks correspond to long lived resonances associated with "horseshoe" type states, as demonstrated by two-dimensional calculations. These resonances have a significant probability density for the linear geometry in which the Ne atom is inserted between the two bromine atoms. At this configuration the exchange of vibrational energy is rather inefficient which explains both why the spectrum is so sparse and resonances are so narrow. Above the Br2 dissociation threshold, the recombination of Br2 is found to be very inefficient, except for very low kinetic energies. The small recombination probabilities are due to vibrational couplings and not to any collisional caging effect. Since the complex remains essentially T-shaped during dissociation, extensive two-dimensional calculations are performed for longer times to better determine final vibrational distributions at low kinetic energies. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1386648
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