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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 2484-2491 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    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 112 (2000), S. 670-685 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrationally state-resolved differential cross sections (DCS) and product rotational distributions have been measured for the Cl+HD(v=1, J=1)→HCl(DCl)+D(H) reaction at a mean collision energy of 0.065 eV using a photoinitiated reaction ("photoloc") technique. The effect of HD reagent rotational alignment in the Cl+HD(v=1, J=2) reaction has also been investigated. The experimental results have been compared with exact quantum mechanical and quasiclassical trajectory calculations performed on the G3 potential energy surface of Allison et al. [J. Phys. Chem. 100, 13575 (1996)]. The experimental measurements reveal that the products are predominantly backward and sideways scattered for HCl(v′=0) and HCl(v′=1), with no forward scattering at the collision energies studied, in quantitative agreement with theoretical predictions. The experimental product rotational distribution for HCl(v′=1) also shows excellent agreement with quantum-mechanical calculations, but the measured DCl+H to HCl+D branching ratio is near unity, which is at variance with the theoretical calculations that predict about 3 times larger yield of HCl+D at these collision energies. The reactivity shows a marked dependence on the direction of the HD(v=1, J=2) rotational angular momentum, and experimental measurements of this reagent alignment effect are in good agreement with theoretical predictions. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 30-34 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Collision-induced dissociation of peptide ions yields „sequence“ ions arising from dissociations of the peptide backbone. Recently, Biemann and his collaborators have elucidated fragment ions involving cleavage of all or part of the side-chains, and have characterized them as remote-site fragmentations of the type investigated for other molecular species by Gross et al. The present work reports results of experiments conducted using a tandem, hybrid mass spectrometer, and devoted to investigating whether remote-site fragmentations (including side-chain cleavages for peptide ions) can be observed for collision energies substantially lower than the keV range used previously. It was found that (laboratory-frame) collision energies of at least 200 eV, and preferably greater, are required for the formation of such fragments. At collision energies in this range the transmission efficiency of the qQ assembly is much lower than for the more usual range of a few tens of eV; this drop in transmission efficiency becomes increasingly severe with increasing mass of the precursor.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 267-272 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The collision-induced dissociation (CID) of Cs4I3+ to form Cs3I2+ has been investigated by mass-analysed ion kinetic energy spectroscopy, When helium was used as collision gas the CID process was accompanied by sizable loss of translational energy in the collisional-activation step. However, use of krypton or xenon as collision gas yielded product ions with translational energies higher than that observed for unimolecular reaction in the absence of collision gas. Neon and argon provided intermediate behaviour. Extensive experiments designed to investigate possible explanations for these observations left superelastic collisions of an excited state as the only possibility. Since nothing is known about the structures and electronic states of species like Cs4I3+, the necessarily speculative discussion is based upon general considerations of coupling of translational and electronic energies via crossings between states of the transitory collision complex. These observations emphasise the complexity of the possible processes which can occur as a result of collisions in the keV range.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 224-228 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 364-372 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Collision induced dissociation (CID) experiments using RF-only quadrupole collision cells normally employ laboratory-frame collision energies Elab of a few tens of eV. Difficulties in inducing CID reactions for larger precursors (〉 600-800 Da) can be attributed in part to collision energies, in the appropriate centre-of-mass reference frame, which are too low. Attempts to overcome this problem by using values of Elab in the range of a few hundreds of eV have been largely unsuccessful. The present work shows that a major reason for this lack of success has been an inability of the instruments used to fulfil the focusing requirements of an RF-only quadrupole cell for such precursors, and their higher mass fragments, in this range of values for Elab. A simple modification permitting use of much higher values of the RF amplitude has been shown to permit the collision cell to be operated so that the ion-beam profile at the entrance aperture is imaged at the exit; improvements in precursor transmission efficiency by up to two orders of magnitude are thus obtainable. Examples of corresponding improvements in fragment-ion spectra of a test octapeptide are also demonstrated. The principal drawback of this approach concerns the poor transmission for low-mass fragments near the stability cut-off (Mathieu parameter qu 〉 0.91); reasons for the non-zero transmission efficiency for fragments with qu 〉 0.91 are discussed, together with methods for alleviating the low-mass transmission problem.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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