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  • 1
    Electronic Resource
    Electronic Resource
    Back to the roots of "channel three'': Rotationally resolved spectra of the 610130 band of C6H6 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 967-978 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved fluorescence excitation and resonance enhanced multiphoton ionization (MPI) spectra of the 610130 one-photon band of benzene at the onset of "channel three'' are reported. The fluorescence decay is monitored after rotationally selected excitation and a large variation of the nonradiative decay time (〈1 to 6.8 ns) is found for the different rotational states at the vibrational excess energy of 3287 cm−1 in S1. The rotational structure of the fluorescence excitation spectrum and the MPI spectrum measured with delayed laser pulses differ considerably. All observed lines of the MPI spectrum were assigned and the rotational line structure can only be understood with a model which incorporates interference between different decay channels. Due to this interference, particular rotational states decay fairly slowly and give rise to lines in the spectrum while states with neighboring rotational quantum numbers decay rapidly and are therefore not found in the spectrum. The previously reported drastic increase of the electronic, nonradiative decay of benzene in this region of excess energy, which led to the postulation of "channel three,'' cannot be confirmed. Instead, the optically excited rovibronic states are thought to be coupled to background states within S1 which are themselves broadened due to strong coupling to the highly excited S0 electronic state rather than due to an unknown ("channel three'') or isomerization process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459123
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  • 2
    Electronic Resource
    Electronic Resource
    Structure of the benzene–Ar2 cluster from rotationally resolved ultraviolet spectroscopy (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7689-7699 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved spectra of the two vibronic bands 610 and 1620 and a vibronic van der Waals band of the benzene–Ar2 cluster are presented, whose vibronic assignments are based on the analysis of their rotational structures. A fit to the rotational line positions in the symmetric top spectra yields an accurate set of rotational constants in the ground and the excited electronic state and the exact values for the band origins of the bands. From these values the spectral shift between corresponding cluster and monomer bands as well as the frequency of the van der Waals symmetric stretching vibration in the excited electronic state are precisely determined. The structure of the cluster is identified to be symmetric with one Ar atom located on the C6 axis on each side of the benzene ring at a distance of 3.58 A(ring) in the S0 state and 3.52 A(ring) in the S1 state. These bond lengths exactly agree with our recent values for benzene–Ar. From the result that the bond lengths are equal for the dimer and the trimer we conclude that there is no Ar–Ar interaction through the intermediate benzene ring plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460154
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  • 3
    Electronic Resource
    Electronic Resource
    Rotationally resolved spectra of the 610 and 610110 band of benzene in a moderately cold molecular beam: Spectral and dynamical analysis (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 4555-4563 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved spectra of the 610 and 610110 band of benzene, C6H6, in a supersonic molecular beam at rotational temperatures between 8 and 50 K are reported. The spectra consist of lines of 85 MHz linewidth. An unexpectedly low saturation intensity of ≈104 W/cm2 is found for the observed one-photon transitions, and it is shown that the saturation intensity differs for different rotational lines within one vibronic band. The rovibronic line spectra are analyzed within the framework of a rigid symmetric top model and highly precise values of the rotational constants are determined. In addition, the rotationless transition frequencies ν00 are obtained with high precision. The spectrum of the 610 band shows no signs of rotational perturbations, while the 610110 band at higher vibrational excess energy shows indications of perturbations for lines with K' above 10. The decay times of single rotational states within the 6111 vibronic state are reported and no rotational dependence of the decay time is found in agreement with the statistical limit character of the interstate nonradiative process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456743
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  • 4
    Electronic Resource
    Electronic Resource
    Rotationally resolved ultraviolet spectrum of the benzene–Ar complex by mass-selected resonance-enhanced two-photon ionization (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 90-96 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution laser excitation was combined with the technique of mass-selected two-photon ionization via a resonant intermediate state to measure rotationally resolved UV spectra of benzene–Ar van der Waals clusters. When the second laser pulse in the two color experiment is delayed by 7 ns no line broadening due to the second ionizing absorption step is observed. Spectra of three vibronic bands in the S1 ←S0 transition of benzene (h6)–Ar and benzene (d6)–Ar were measured yielding a line spectrum with a linewidth of 130 MHz. Resolution is sufficient to demonstrate that no asymmetry splitting of the rotational lines occurs and the spectrum is to a high precision that of a symmetric rotor. A detailed analysis of the rotational structure yields an accurate set of rotational constants. We find that the Ar is located on the C6 rotational axis. Its distance from the benzene ring plane is 3.582 A(ring) in the electronic ground state and decreases by 59±3 mA(ring) in the electronically excited state due to the increased polarizability of the benzene molecule after electronic excitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458394
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  • 5
    Electronic Resource
    Electronic Resource
    Structure of Amorphous MoS3 (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 9194-9200 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100022a037
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  • 6
    Electronic Resource
    Electronic Resource
    Rotationally resolved vibronic spectra of the van der Waals modes of benzene–Ar and benzene–Kr complexes (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 865-881 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rotationally resolved vibronic spectra of eight van der Waals bands built onto the 610 transition of the bare molecule are reported for the complexes C6H6⋅Ar, C6D6⋅Ar, and C6H6⋅84Kr. The rotational structure of most of the bands is identified as that of a perpendicular transition with Coriolis coupling constants nearly the same as those of the 610 band of the respective complex. We therefore conclude that the excited van der Waals modes of the three complexes have a1 symmetry. Precise rotational constants are fitted to the large number of unblended lines assigned in each spectrum. In contrast, the lowest energy van der Waals bands of both C6H6⋅Ar and C6D6⋅Ar display a completely different rotational structure which can neither be explained by a genuine perpendicular nor a genuine parallel transition. This situation will be analyzed in detail in accompanying work and the final vibronic assignments deduced. The rovibronic lines in all the spectra show a linewidth of 130 MHz that is solely due to the laser linewidth and to residual Doppler broadening in the molecular jet. It is concluded that the excited vibronic combination states of intramolecular and van der Waals vibrations do not predissociate on the nanosecond time scale of our experiment. Two of the reported spectra show irregularities in the rotational structure that are explained by coupling to adjacent combination states. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470811
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  • 7
    Electronic Resource
    Electronic Resource
    Correlated electron emission in multiphoton double ionization (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 405 (2000), S. 658-661 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Electronic correlations govern the dynamics of many phenomena in nature, such as chemical reactions and solid state effects, including superconductivity. Such correlation effects can be most clearly investigated in processes involving single atoms. In particular, the emission of two ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35015033
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  • 8
    Electronic Resource
    Electronic Resource
    Modulated Structure of the Composite Crystal Urea/n-Heptadecane (1997)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 53 (1997), S. 544-552 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The structure of the composite crystal urea/heptadecane was determined by single-crystal X-ray diffraction. The lattice constants of the hexagonal substructures are a = 8.218 (2), b = 8.218 (3), ch = 11.017 (3) Å for the urea (host) structure and cg = 23.713 (1) Å for the heptadecane (guest) structure, respectively. The (3+ 1)-dimensional space group is P6122(00\rho)011. Refinements on 786 reflections converged to wR = 0.0232 for 608 main host reflections, wR = 0.1506 for 10 main guest reflections, wR = 0.0328 for 49 common main reflections and wR = 0.753 for 119 pure satellite reflections. A comparison of the refinement of only the urea substructure and a refinement of the whole composite crystal, including the guest subsystem and the mutual modulations of both subsystems, shows that the main reflections, previously assigned to the urea host exclusively, are affected by a nonnegligible contribution of the heptadecane satellite scattering. The modulation of the guest structure has a maximum when the CH2 groups of the heptadecane molecule are facing the channel walls at heights corresponding to troughs in this wall. Thus, the modulation of the guest structure can be interpreted by an adaptation of the guest molecules to the host structure. The modulation of the host structure was found to be very weak, as the satellite scattering of the host structure is low. \psi-scans of the 00 l reflections revealed that the observed violation of the 61 screw axis extinction rule of the host structure and guest structure modulation can be explained by considerable umweganregung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768196014966
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  • 9
    Electronic Resource
    Electronic Resource
    Cytokine modulation of basophil histamine release in wasp-venom allergy (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Allergy 49 (1994), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report the effect of interleukin-3 (IL-3) and of other cytokines on antigen-induced basophil histamine release in wasp-venom-allergic subjects. Leukocytes from 12 patients with documented anaphylactic sensitivity to wasp venom were preincubated in the presence or absence of IL-3, granulocyte/macrophage-colony stimulating factor (GM-CSF), IL-5, IL-8, or stem cell factor (SCF). Washed cells were then exposed to venom and to other secretagogues, and histamine release in the supernatant was measured fluorometrically. Preincubation of leukocytes with IL-3, GM-CSF, or IL-5 (0.02–2 ng/ml), but not with IL-8 and SCF, caused a dose-dependent enhancement of antigen-induced basophilic histamine release in all subjects tested. Mean maximum increase was about 100% for IL-3, IL-5, and GM-CSF. The priming effect of IL-3 was rapid, persisted up to 12 h, and was not accompanied by a change in cellular histamine. IL-3 had a comparable enhancing effect when basophils were triggered with anti-IgE or N-formylmethionylphenylalanine (FMP). By contrast, IL-3 had no effect on substance-P-induced histamine release. The significant enhancement of basophil releasability to antigen in wasp-venom allergy by very low concentrations of IL-3, GM-CSF, and IL-5 suggests that cytokines in the basophil (mast-cell?) microenvironment could be critical factors in determining the variability of sting reactions in Hymenoptera-venom-allergic subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1398-9995.1994.tb00133.x
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  • 10
    Electronic Resource
    Electronic Resource
    Evidence for different immune responses to HIV in CSF and serum? (1987)
    Springer
    Journal of molecular medicine 65 (1987), S. 259-263 
    Details
    ISSN: 1432-1440
    Keywords: Acquired immune deficiency syndrome ; Cerebrospinal fluid antibody quantitation ; Western blot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of acquired immune deficiency syndrome (AIDS) and a case of AIDS-related complex (ARC) are described. In both instances comparative Western blot analysis of cerebrospinal fluid (CSF) and serum samples show evidence of qualitative differences in antibody-binding patterns to viral polypeptides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01773445
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