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  • 1
    Electronic Resource
    Electronic Resource
    The detection of fast neutral fragments following the photodissociation of krypton cluster ions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6412-6421 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mass and kinetic energy resolved krypton cluster ions, Kr+n, have been photodissociated in the entrance to a time-of-flight (TOF) device of variable length. The subsequent deflection of all ions allowed for time resolved measurements to be undertaken on the neutral photofragments. Following the absorption of a photon (hν=2.33 eV), all cluster ions up to Kr+25 were found to eject one or, possibly, two neutral atoms with relatively high kinetic energies. An analysis of the laser polarization dependence of this event showed that the atoms are ejected on a time scale which is short compared with the rotational period of a cluster (10–100 ps). Remaining internal energy within the cluster ions is dissipated through the further loss of neutral atoms, but with low kinetic energies. The latter process is found to be isotropic with respect to the angle of polarization of the laser radiation. Kinetic energy releases calculated from the TOF spectra exhibit a gradual decline as a function of cluster size out as far as Kr+13 and, thereafter, maintain a constant value. This pattern of behavior is significantly different from that observed previously [Smith et al., J. Chem. Phys. 97, 397 (1992)] for argon cluster ions, Ar+n. A careful analysis of the kinetic energy data for Kr+3 photodissociation reveals that, in at least one of the reaction paths, the Kr+ fragment can only be formed in the ground spin–orbit state. This observation implies that photofragmentation proceeds via a 1(1/2)g←1(1/2)u transition. The implications of this result for the analogous Ar+3 photofragmentation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467050
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  • 2
    Electronic Resource
    Electronic Resource
    Photoneutral–photoneutral coincidence study of Ar+3 (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 474-476 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A coincidence technique has been used to correlate the motion of the two neutral fragments (argon atoms) that result from the photodissociation of Ar+3. An analysis of the results reveals the presence of two separate dissociation channels. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469613
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  • 3
    Electronic Resource
    Electronic Resource
    Infrared photofragmentation spectra of size-selected SF6⋅Ar+n cluster ions (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 5177-5193 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Results are presented of a detailed experimental study of the infrared photofragmentation patterns of size-selected SF6⋅Ar+n cluster ions for n in the range 3 to 70. Line-tuneable CO2 and N2O lasers have been used to excited the ν3 vibrational mode of the SF6 molecule which is followed by the loss of one and two argon atoms as the principal fragmentation routes. Which of the two processes is dominant depends quite strongly on the size of the cluster ion concerned, with very pronounced fluctuations in the relative intensities of photofragments being observed for cluster ions in the range SF6⋅Ar+3 to SF6⋅Ar+25. Only for SF6⋅Ar+3 is the fragmentation pattern markedly different from that found for the other ions; an observation that supports an earlier conclusion regarding the relative ionisation energies of the two constituents [Stace et al. J. Phys. Chem. 97, 11363 (1993)]. A summation of fragment ion intensities as a function of laser wavelength is used to determine infrared absorption profiles and these have been recorded for individual clusters containing up to 70 argon atoms. Clusters containing fewer than 40 argon atoms appear to form single structures, with both the absorption profile shapes and selected hole-burning experiments suggesting that the number of isomers is small.The presence of isomers only appears to become significant when the clusters contain more than 40 argon atoms. The observation of site splittings for the triply degenerate ν3 vibrational mode of SF6, together with the comparatively narrow linewidths seen for clusters containing between 15 and 40 rare gas atoms, indicates the presence of ordered structures. Such a conclusion implies that the clusters are solidlike rather than liquidlike. Overall, the results demonstrate that there is a clear correlation between those criteria previously used to identify the presence of stable cluster ion structures, i.e., mass spectra and unimolecular fragmentation patterns, and the corresponding infrared fragmentation patterns and absorption profiles. Of the ions studied, SF6⋅Ar+21 stands out as being particularly stable and worthy of future theoretical attention. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470555
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  • 4
    Electronic Resource
    Electronic Resource
    Infrared laser-induced photofragmentation of the positive and negative ions of size-selected SF6 (NO)n clusters (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 9436-9446 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A detailed study has been undertaken on the infrared photofragmentation of SF6(NO)±n cluster ions. A line-tuneable CO2 laser has been used to excite the ν3 vibrational mode of the SF6 molecule which is followed by the observation of three separate fragmentation channels: –SF6, –NO, and –2NO. The relative intensities of the fragments are found to be sensitive to the sign of the charge on the ion, the cluster size, and whether n is either odd or even. Within clusters of the same charge, the most marked transitions in fragmentation pattern are found between odd- and even-sized cluster ions, with the decay channels favoring those processes which lead to the formation of even electron ions. There are also large differences in fragmentation pattern between the negatively and positively charged ions. A summation of fragment ion intensities as a function of laser wavelength is used to determine infrared absorption profiles and their shapes confirm a pronounced difference in behavior between SF6 (NO)−n and SF6 (NO)+n. The results for the positively charged ions are interpreted in terms of a central (NO)+3 core which serves to fix the position of the SF6 molecule via an attractive ion-induced dipole interaction. In contrast, observations on the negatively charged ions, suggest that the interaction between the excess electron and the SF6 is predominantly repulsive and also sufficiently diffuse as to keep the molecule comparatively mobile even in large cluster ions. It is suggested that the excess electron in SF6 (NO)−n may occupy a surface state and that the state has associated with it approximately 15 NO molecules. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467975
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  • 5
    Electronic Resource
    Electronic Resource
    Infrared-induced charge transfer in sulfur hexafluoride-argon cluster (SF6.cntdot.Ar3+: an alternative route to the ionization energy of SF6+ (1993)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 11363-11365 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100146a001
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  • 6
    Electronic Resource
    Electronic Resource
    Laser-Induced Infrared Photofragmentation of SF6·(C6H6)n+ Cluster Ions (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 6333-6339 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100017a012
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  • 7
    Electronic Resource
    Electronic Resource
    Covariance images of the primary response from rare gas cluster ions to photoexcitation (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1367-1372 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photoexcitation and fragmentation of rare gas cluster ions can yield large numbers of neutral products which, in turn, exhibit considerable variation in their kinetic energies. In order to interpret such events, a coincidence technique has been used to correlate the arrival times of neutral photofragments at a detector following the photoexcitation of Arn+ and Krn+, for n≤10. By collecting data from approximately 105 photodissociation events for each type of cluster ion, covariance images have been derived which clearly demonstrate that the initial response to photoexcitation, is the ejection of a single rare gas atom which carries with it between 30% and 60% of the excess energy. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473305
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  • 8
    Electronic Resource
    Electronic Resource
    Photochemical Processes on Arn.cntdot.C4H6+ Cluster Ions for n in the Range 1-40 (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 4473-4474 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00089a045
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  • 9
    Electronic Resource
    Electronic Resource
    The decay dynamics of photoexcited rare gas cluster ions (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 959-968 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetic energies of fast neutrals ejected from photoexcited rare gas cluster ions have been measured for the following systems: Arn+, Krn+, Xen+ at two photon wavelengths: 355 and 532 nm, and for n in the range 2–19. New data are presented for xenon at both wavelengths, and for argon and krypton cluster ions at 355 nm. For argon and krypton cluster ions at 532 nm, new data have been recorded which are more accurate than those presented previously. A Monte Carlo model of the experiment has been used to simulate the kinetic energy releases and also to investigate variations in the scattering anisotropy parameter (β) as a function of photon energy and cluster composition and size. Significant fluctuations in β are observed, and these are attributed to a combination of structural variation and changes to the nature of the central chromophore. For small cluster ions the kinetic energy release data show evidence of being influenced by the final spin-orbit state of the atomic ion. Overall, there is a gradual decline in kinetic energy release as a function of increasing cluster size; however, there are marked variations within this trend. For all three rare gas systems the results show that the primary response to photoexcitation is the ejection of a single atom with a high kinetic energy on a time scale that is short compared with the rotational period of a cluster. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479378
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  • 10
    Electronic Resource
    Electronic Resource
    Towards a complete description of multiple dissociation events: A photoion–photoneutral (pi-pn3) coincidence study of Ar4+ (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 5803-5811 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By combining the techniques of ion and fast neutral detection into a single coincidence experiment, it is demonstrated that the scattering patterns of all the fragments from a multiple dissociation event can be correlated. The power of this new technique is demonstrated using Ar4+ as an example, where photoexcitation generates a total of 7 possible reaction products, each of which is, in theory, distinguishable by charge and/or kinetic energy. The two ionic products are Ar+ and Ar2+, and whilst the latter ion emerges with a low kinetic energy and is isotropically scattered, Ar+ has associated with it both a significant spread in laboratory-frame kinetic energy and features indicative of anisotropic scattering. By selecting an appropriate laboratory-frame kinetic energy for either ion, coincident neutrals can be identified and energy-analyzed using a time-of-flight technique. The method reveals the presence of two separate fragmentation channels, one of which is concerted and the other sequential. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477202
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