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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1009-1020 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental studies on the photodissociation of F2 in 12 K crystalline argon solids are reported, and compared with molecular dynamics (MD) simulations of the same system. At excess energies above 2.5 eV,the dissociation probability is near unity, in agreement with theory. At the longest experimentally accessible wavelength for photodissociation, 450 nm, which corresponds to a dissociation excess energy of 1.16 eV, the permanent dissociation probability is reduced to 0.05. This is an order of magnitude smaller than that predicted by the simulations. Possible sources for this discrepancy are discussed. Long range migration of F atoms, predicted by MD simulations, is demonstrated to occur both upon photodissociation of F2, and upon relaxation of argon fluorides. In the latter case, it is shown that with the initial impulse, the F atoms migrate on average a length of ∼70 A(ring) in the lattice. The thermal recombination of F atoms in both solid Ar and Kr are also characterized. The experimental studies are conducted in free standing crystals of argon, by following the photogeneration of F atoms. This is accomplished by monitoring the argon fluoride emissions upon charge transfer excitation over the ArF(B←X) excitation at 193 nm. Two distinct charge transfer states contribute to the observed emission. The first, with an emission maximum near 315 nm and a lifetime of 180(±10) ns, is assigned to Ar2F. The second with a maximum at 355 nm and a lifetime of 700(±50) ns is assigned to Ar6F stabilized by trapping of F atoms in interstitial sites. Pump–probe measurements indicate a strong transient absorption from both of these states, precluding the possibility of observing any stimulated emission over these exciplexic transitions in the solid state.
    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 94 (1991), S. 1692-1697 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: XeF doped solid Kr represents a novel solid state exciplex laser. A net gain in excess of 100 cm−1 and a superradiant beam of 5 mrad divergence are observed over the XeF(D→X) transition at 301 nm, when free standing crystals of XeF doped Kr are optically pumped near the XeF(D←X) absorption maximum at 260 nm. Superlinear dependence of gain on pump intensity and low divergence of the amplified beam are taken as evidence for self-focusing. The XeF(D) state is effectively isolated from the lower manifold of charge transfer states in solid Kr, which includes XeF(B,C) and (KrXe)+F−.
    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 94 (1991), S. 7819-7831 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Long-range migration of F atoms upon photodissociation of F2 is demonstrated in mixed F2@B:Xe@B:Kr solids by monitoring arrival of F atoms at Xe sites. The impulsive migration probabilities are wavelength dependent. At excess energies above 2.4 eV migration lengths spanning 15 lattice sites are observed. Migration is not observed for excess energies below 1.9 eV. The photodynamics of charge transfer states in F:Xe:Kr solids is presented. Both diatomic Xe+F−, and mixed triatomic (KrXe)+F− exciplexes are observed. The XeF(C) and (KrXe)+F− states are strongly coupled and decay radiatively with a lifetime of 80 ns. These states are populated via excited vibrations of XeF(B) and XeF(D). A crossing between XeF(D) and KrXeF potentials is identified. Above this crossing the lower manifold of charge transfer states are directly populated, while a delay of 10 ns is observed below the crossing. XeF(B, v=0) remains uncoupled from the rest of charge transfer states. Implications with respect to solid state exciplex lasers are discussed.
    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 92 (1990), S. 4856-4875 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation of F2 in crystalline Kr is subject to only a minor cage effect—quantum yield of 0.5 at 308 nm, at T=12 K. Two-photon-induced harpooning in the same system leads to dissociation with near unit quantum efficiency; it is shown that this absorption is coherent with a giant cross section of 3(±2)×10−45 cm4 s at 275 nm. Excitation and emission spectra of charge-transfer transitions in solid Kr doped with F atoms, and solid Ar multiply doped with F/Kr are reported. The vertical excitation in F/Kr leads to a state delocalized over immediate neighbors—assigned to Kr+6F−. This state localizes on a subpicosecond time scale to the triatomic Kr+2F− configuration. The latter relaxes radiatively (τr=140 ns), to the repulsive wall of the ground state (∼1 eV above ground). The excitation in F:Kr/Ar solids shows the diatomic KrF(B←X) resonances. From the analysis of the spectrum, a harmonic frequency ω=75(±3) cm−1 is extracted for F atoms in the ground state, consistent with molecular-dynamics simulations of an octahedrally trapped F atom [ω=70(±1) cm−1]. The diatomic KrF(B) state relaxes on a time scale of 20 fs〈t〈500 fs to the mixed triatomic configuration, (ArKr)+F−, which then relaxes radiatively (τr=60 ns). The kinetic energy released upon the radiative dissociation of triatomic exciplexes generates acoustic waves, and defects, and leads to mass transport. The modes of propagation of the acoustic waves, their subsequent thermalization, and self-annealing of the solid, are directly monitored by spatially and temporally resolved transient scattering experiments. A transient loss (σ(approximately-equal-to)10−17 cm2), the origin of which is not fully understood, is observed for Kr2F isolated in solid Kr. The mass transport, and long-range migration of F atoms (∼10 lattice sites), is directly monitored in multiply doped Ar solids in which the shuttle of F atoms between Xe and Kr centers can be demonstrated.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 149 (1988), S. 145-149 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 208 (1993), S. 247-255 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 171 (1990), S. 423-429 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 8698-8703 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analytical potential energy surface (PES) along the stretching coordinates of a linear XeHXe+ ion is presented. Ab initio calculations within the effective core potential approach are used as input for the PES. The present vibrational analysis indicates extensive mixing of the zeroth-order harmonic oscillator vibrational states, and a rather complete collapse of the normal mode picture already near the bottom of the potential well. At higher vibrational energies, and elongated Xe–Xe distances, development of a double minimum in the PES is observed. The simulated absorption spectrum consists of a strong vibrational progression near 1000–1700 cm−1, and is in qualitative agreement with the previous matrix isolation data. The intensity distribution of the vibrational progression is mostly due to the potential terms rather than nonlinear contributions in the Taylor series expansion of the electric dipole moment. Due to the highly anharmonic potential, and subsequent breakdown of selection rules, the emission spectrum is predicted to be particularly rich in the 850–1500 cm−1 spectral region. Several of the vibrational transitions possess transition dipoles exceeding 1 D.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 5630-5635 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Delocalized charge-transfer excitations in solid xenon multiply doped with atomic halogens (I, Br, Cl) and hydrogen are demonstrated to lead to charge separation by trapping of the positive charge. As evidence of such a concept we present the first vibrational spectra of Xe2H+ and Xe2D+, which are believed to be vibrationally bound ions.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Molecular Structure: THEOCHEM 200 (1989), S. 93-101 
    ISSN: 0166-1280
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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