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  • 1
    Electronic Resource
    Electronic Resource
    Argon, krypton, and xenon excimer luminescence: From the dilute gas to the condensed phase (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1469-1477 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: For the first time, the evolution of luminescence from rare gases was studied as a function of number density. Synchrotron radiation served as a light source for selective and pulsed excitation of the samples. The excitation spectra confirm previous results on perturbed Rydberg states and exciton appearance in dense media. In time-resolved emission spectra the peak energies and widths of the luminescence bands were followed. The energy separation between the fast and slow components is found to be density independent. A model proposed by Cheshnovsky et al. [Chem. Phys. Lett. 15, 475 (1972)] accounts for the change in peak width with temperature. Both lifetimes decrease with increasing density. The data extrapolate to 3.3±0.1 ns (Ar); 3.4±0.1 ns, 270±5 ns (Kr); 4.5±0.1 ns, 100±5 ns (Xe) for the low density limit. For the solid at the triple point, we obtain 1.3±0.1 ns, 82±5 ns (Kr) and 1.1±0.1 ns, 18.5±0.5 ns (Xe). Theories on density dependence of lifetimes give only a qualitative description of the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457108
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  • 2
    Electronic Resource
    Electronic Resource
    Vacuum ultraviolet spectroscopy of the Cl2 molecule trapped in pure neon, pure argon, or mixed neon–argon matrices (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6020-6028 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Synchrotron radiation excitation and emission spectra with lifetime measurements are reported for the first time in the VUV region for systems consisting of Cl2 molecules trapped in a neon matrix, an argon matrix, and mixed Ar/Ne matrices. In pure neon, the emission spectrum of the D'→A' "laser'' transition at 4.7 eV of the Cl2 molecule is vibrationally well resolved and constitutes an interesting example of UV spectroscopy of a matrix "isolated'' molecule. In pure argon or mixed Ar/Ne matrices, new broad emissions at 4.1, 3.8, and 3.5 eV are clearly identified, which result from the specific interaction between Cl@B|2 and Ar and are attributed to different charge–transfer states of the ArCl+Cl− entity. The Ar concentration dependence and the time-gated spectra are shown to be especially useful in interpreting the large differences observed between the pure neon and the pure argon matrix case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457419
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  • 3
    Electronic Resource
    Electronic Resource
    Mirror concepts of the new wiggler and undulator beamlines at HASYLAB : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2099-2101 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The mirror concept of the new HASYLAB bypass beamlines has as its main design goal the handling of the large radiation power of up to 7 kW from wigglers and undulators. The first optical element is a SiC-coated graphite mirror which acts as an energy low pass filter. The choice of the material, the cooling scheme, the mirrorchamber design, and the additional focusing mirrors are described. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145740
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  • 4
    Electronic Resource
    Electronic Resource
    Photocurrent excitation spectra of methyl iodide/methane fluid mixtures (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 187-193 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Impurity photocurrents of fluid CH4:CH3I were studied in the region of the (2E1/2)nd Rydberg series of CH3I and also beyond the 2E1/2 ionization potential up to the LiF cutoff. In the gas, a step-like rise of the photocurrent was observed at a photon energy somewhat lower (by about 20 meV) than the 2E1/2 ionization potential, indicating that high members of the (2E1/2)nd Rydberg series of methyl iodide can be ionized by further processes besides the well-known autoionization into the 2E3/2 continuum. At the high-energy side of the 2E1/2 limit further peaks appear, corresponding to simultaneous excitation of (2E1/2)nd Rydberg states and one or two quanta of the ν2(a1) vibration of CH3I. In the photon energy region of 10.8–11.8 eV a series of at least eight peaks were observed, due to excitation of vibronic levels of the Jahn–Teller split 4s Rydberg state of methane. The value of the adiabatic ionization potential 2E3/2 of CH3I in liquid CH4 near the critical point was found to be 8.30 eV, while in neat dilute CH3I gas it is 9.48 eV. The overall variation of 2E3/2 in the liquid phase (from 190 to 132 K, 6.4×1021 to 1.5×1022 cm−3) is 70 meV. In the densest (and coolest) liquid samples studied a series of peaks, with intervals of ≈60 meV appeared in the photon energy range 8.37〈hν〈8.5 eV on top of the continuous background.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468168
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of methane on photocurrents generated by exciting xenon below its first ionization potential (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 4628-4634 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photocurrent excitation spectra of xenon and of the xenon–methane absorber–perturber system were studied in cells equipped with LiF windows cooled to ≈−30 °C. The cooling was needed to shift the LiF cutoff so as to enable measurements at photon energies up to the first ionization potential of Xe (12.13 eV). The spectra observed in methane–xenon mixtures were essentially similar to those in neat xenon, demonstrating that the Hornbeck–Molnar process (excitation of a xenon atom–excimer formation–ionization of an excimer) is feasible even in the presence of the molecular perturber CH4 at pressures up to ≈ 105 Pa. The primary effect of CH4 is to decrease the photocurrent, since photons in the energy range in question are absorbed by the methane molecules as well, without photoionizing them. The dependence of the current on methane concentration showed that the above mechanism is not the only one by which methane quenches the current. Moreover, the degree of quenching of the current by methane is dependent on the photon energy. The analysis of this dependence led to the assumption that an excited xenon atom and a methane molecule may form an excimer. Previous results on the Ar:Xe and Kr:Xe systems support this assumption. Peak inversions observed at high pressures in neat xenon, but absent in the CH4:Xe system, are discussed on the basis of prevailing models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467451
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  • 6
    Electronic Resource
    Electronic Resource
    Exciplex vacuum ultraviolet emission spectra of KrAr: Temperature dependence and potentials (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 9021-9026 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472736
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  • 7
    Electronic Resource
    Electronic Resource
    Spectroscopy of ionic alkali rare gas excimers in matrices (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 3920-3925 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using a clean preparation technique of doping alkali atoms in argon matrices, VUV emissions of the charge-transfer states of the ionic xenon–alkali excimers (XeA)+ have been measured. With synchrotron radiation as an excitation source, the ionic species were generated in the matrix and energy and time-resolved spectroscopy has been performed with synchrotron radiation as an excitation source. The emissions of the charge-transfer reaction: (Xe+A)→(XeA+)+hν have been observed for all ionic (XeA)+ excimers with energies in the VUV range between 6.05 and 7.4 eV. The excitation spectra revealed a primary formation process through direct ionization of the xenon; however, neutral xenon resonance states are also contributing. As obtained from lifetime measurements, the bands are assigned to the 0I−→0+ transition of the fine-structure components which account for the long decay time. An increase of the xenon concentration favors the formation of ionic trimers (Xe2A)+ whose emissions have also been identified. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473782
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  • 8
    Electronic Resource
    Electronic Resource
    Luminescence from pure and doped solid deuterium irradiated by keV electrons (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 126-134 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Solid samples of pure and doped deuterium were irradiated by keV electrons and the luminescence of these samples was measured between 200 and 700 nm. In order to separate the intrinsic emissions from impurity-induced luminescence, deuterium was doped with standard air impurities like N2, H2O, O2, and CO. In purified solid deuterium, an emission at 275 nm was observed for the first time and attributed to a transition in D*3 molecules produced via ionization of D2, formation of D3+, and subsequent recombination with electrons. Film-thickness dependence as well as timing experiments corroborate this interpretation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464661
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  • 9
    Electronic Resource
    Electronic Resource
    Triplet states of CO trapped in rare gas crystals (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 6108-6114 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational progressions due to the a 3Π, a' 3Σ+, d 3Δ, and e 3Σ− states of CO in Ar, Kr, and Xe crystals are observed in absorption. Two groups of phonon sidebands separated from the zero phonon lines by about 4 and 8 meV for the a' 3Σ+ and d 3Δ states are attributed to librations and to localized phonons. The broad absorption bands, the even broader emission bands, and the large Stoke shift of the a 3Π transition are treated in terms of a configuration coordinate model by a momentum analysis. A quadratic coupling has to be invoked with relaxation energies in the excited states increasing from 14 meV for Ar to 95 meV for Xe and with relaxation energies in the ground state increasing from 29 meV for Ar up to 1278 meV for Xe. The changes of the configuration coordinate of 0.2 to 1.5 A(ring) are also discussed with the help of two pair potential models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452449
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  • 10
    Electronic Resource
    Electronic Resource
    Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 420 (2002), S. 482-485 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01197
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