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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6085-6092 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The electronic states of the ionic excimer Ar++2 are calculated using ab initio multireference configuration interaction and effective core pseudopotentials. Among states dissociating into Ar+(2P)+Ar+(2P), all are found to be repulsive, except the ground state, which occurs to be quasibound near Re=4.1a0 with a well depth of ≥230 cm−1. All states originating from Ar++(3P,1D,1S)+Ar are bound with dissociation energies in the range 3200–4500 cm−1 and equilibrium distances between 5.6a0 and 6a0. Simulation emission spectra from bound excited states are derived from the calculated potentials and the possible contribution of the Ar++2 ion to the third continuum fluorescence is discussed.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 7646-7655 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The electronic structure of BaH is investigated using a 10-electron relativistic pseudopotential on Ba, frozen core configuration interaction (CI) with three active electrons and core-polarization potential. Fine structure is taken into account with a semiempirical spin–orbit operator. The electronic properties of all states dissociating into Ba(6s2,6s15d1,6s16p1) +H(1s) are obtained and generally found in agreement with experiment within 0.03 A(ring) for equilibrium distances, 300 cm−1 for transition energies, 30 cm−1 for vibrational frequencies, except for the D 2Σ+ state. The methodology used in this work is discussed in the light of the results presented here.
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  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 6093-6103 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The first Rydberg states of the Ar+2 molecular ion dissociating into Ar+(3p5,2P) +Ar*(3p54s,3,1P) are calculated using multireference configuration interaction and effective core pseudopotentials. At long internuclear distance, their electronic structure is shown to be determined by resonance interaction and the magnitude of the Rydberg electron-transfer integral, inducing long-distance wells with De in the range 0.6–0.8 eV around Re(approximately-equal-to)9.0a0. In the short distance range, the electronic structure can be understood as resulting from an ionic Ar++ core with an outer Rydberg electron, and bound or quasibound Rydberg states are obtained around Re∼4a0. The fluorescence spectra of those states are simulated and the possible intervention of the Ar+2 system in the third continuum spectrum is considered.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6102-6124 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The potential energy curves for all the adiabatic Ω states dissociating into Kr+Kr, Kr+Kr*(5s,5s'), Kr+Kr*(5p), and some higher states are calculated using multireference perturbative CI algorithms (CIPSI/CIPSO) with relativistic averaged and spin–orbit core pseudopotentials. A partially diabatic representation of the potential curves rationalizes the complex features of the adiabatic states induced by numerous avoided crossings. A systematic comparison is carried out with extensive experimental data, including absorption from the ground state, fluorescence data, and transient absorption spectroscopy.
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  • 5
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 1500-1515 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A pseudopotential hole-particle model (corresponding to the formalism introduced in paper I) is applied to the determination of the Rydberg states of the Ar2* excimer with and without spin–orbit coupling. All the Λ–Σ Rydberg states (without spin–orbit coupling) adiabatically dissociating into Ar+Ar* (4s,4p,3d,5s,5p,4d), are investigated and all Ω states adiabatically dissociating into Ar+Ar*(4s,4p) have been determined including spin–orbit coupling. The calculation also includes at short distance attractive molecular configurations diabatically correlated with higher atomic asymptotes. The nature of the Λ–Σ states is analyzed and assigned with reference to the Rydberg orbitals of the Kr* united atom limit. Extensive comparison with previous calculations and experiments is carried on. For the lowest ungerade states (1)1u, 0−u, (1)0+u, and (2)0+u, good quantitative agreement is found with experimental high resolution studies. Several members of Rydberg series are calculated and assigned, yielding intra-Rydberg transition energies (1)3Σ+u((1)1u,0−u)→m 3Πg or m 3Σ+g in good correspondence with recent intra-Rydberg spectroscopy experiments. In particular the present calculation provides a likely interpretation of the infrared spectra of Ar2* as due to (1)3Σ+u→(1)3Σ+g transitions with an upper corresponding Ω state (1)1g,0−g containing quasi-bound vibrational levels. © 1996 American Institute of Physics.
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  • 6
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9021-9026 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The temperature dependence of the emissions from the 0+(3P1)and 1(3P2) Kr*Ar exciplex states in the range 85–350 K was studied using time resolved techniques, vacuum ultraviolet synchrotron radiation, and argon samples doped with minimal amounts of krypton. As the temperature is increased, the emission shifts to the blue, its width increases by almost a factor of 2, and the line shape becomes asymmetrical. The experimental line shapes have been simulated by means of Franck–Condon density calculations using the available ground state potential of Aziz and Slaman [Mol. Phys. 58, 679 (1986)] and by modeling the exciplex potentials as Morse curves. The potential parameters for the 0+ and 1 states are re=5.05±0.01 and 5.07±0.01 a0, respectively; De=1150±200 cm−1 and β=1.4±0.1 a0−1 for both states. The latter two values yield ωe=140 cm−1 and ωexe=4.3 cm−1. The energy positions of the exciplexes's wells and their depths are compared with published results. © 1996 American Institute of Physics.
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  • 7
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6426-6438 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The electronic structure of IF is investigated using ab initio pseudopotentials and a variational/perturbative MRCI scheme (CIPSI/CIPSO). All the valence states dissociating into neutral asymptotes I(2P1/2,2P3/2)+F(2P1/2,2P3/2) and ionic asymptotes I+(3P2,3P1,3P0,1D2,1S0) +F−(1S0) are determined up to the region where they undergo avoided crossing with the neutral excited states dissociating into I*+F. The spectroscopic properties are derived and discussed in comparison with the available experimental results, with emphasis on the X, B, E, A, β, A′, and D′ states. © 1996 American Institute of Physics.
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  • 8
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 1492-1499 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A pseudopotential hole-particle formalism is developed for the treatment of rare-gas excimers and excited rare-gas clusters. The formalism relies on the definition of a model Hamiltonian on the basis of single hole-particle excitations (from the neutral closed shell ground state) involving localized np hole orbitals and any orthogonal molecular orbital (MO) basis set for the excited particle. Hole contributions in the Hamiltonian matrix elements are taken into account via distance- and orientation-dependent transfer integrals (hole delocalization) and repulsion integrals like in diatomic in molecules treatments of rare gas ions, while the contribution of the excited particle is included through an explicit quantal treatment via one-electron e-Rg and averaged e-Rg+ pseudopotentials. Core-polarization pseudopotentials are also added to account for core-polarization and core-Rydberg correlation effects. Some approximated core-Rydberg two-electron integrals needed for adequate space and spin multiplicity of the excited states are also included. The possible applications and extensions of this formalism are discussed. © 1996 American Institute of Physics.
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  • 9
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 7884-7892 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: A one-electron pseudopotential model is used to calculate the excited states of NanFn−1 clusters in the range 2≤n≤29. The transition dipole moments are derived to determine the vertical absorption lines from the ground state. Monte Carlo simulations based on the Franck–Condon principle are also achieved to obtain finite temperature absorption spectra. The analysis of ground and excited orbitals in various situations illustrates the rather simple nature of the excitations which are interpreted through an analogy with s−p type transitions in atoms. The influence of electron localization in the initial state is pointed out. Comparison of the simulated spectra with experimental data provides additional keys to understand and discuss the relationship between structure, electron localization, and spectroscopic properties. © 1999 American Institute of Physics.
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  • 10
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4148-4158 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present a calculation of the structure and the optical transitions of sodium atoms and dimers embedded in argon clusters and matrices. We studied several different systems: A single sodium atom in a dodecahedral argon cluster, a Na atom in a substitutional site of a fcc (face-centered-cubic) Ar lattice containing 63 atoms and a sodium dimer in a 9-atom vacancy of the same fcc lattice (Na2@Ar54). For optimizing the system geometry in its ground state, we use a simplified tight-binding scheme of a metal cluster dressed by the metal-matrix and matrix-matrix van der Waals interactions. A procedure closer to ab initio methodology is then applied using e-Na+ and e-Ar semi-local pseudopotentials and core-polarization operators to determine the electronic structure of the metal valence electrons in the environment of the rare-gas atoms. The electronic transitions and oscillator strengths are obtained by a full two-electron configuration interaction (CI) treatment in the case of Na2@Ar54. The A1Σu+→X1Σg+ transition is redshifted in comparison to the free Na2 dimer. This phenomenon does not appear in the case of a matrix-isolated atom, where all lines are blueshifted. © 1998 American Institute of Physics.
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