Victoria L. Ayles

University of Georgia, Athens, GA, United States

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Publications (12)31.76 Total impact

  • W H Breckenridge, Victoria L Ayles, Timothy G Wright
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    ABSTRACT: Evidence is presented that there is a clear covalent component in the bonding of Au+ to Kr and Au+ to Xe, with some evidence that there may be such bonding between Au+ and Ar; for Au+ and Ne, there is no such evidence, and the bonding seems to be entirely physical. A model potential analysis shows that when all attractive inductive and dispersive terms out to R-8 are properly included in the Au+-Ne case, with an Ae(-bR) Born-Mayer repulsive term, essentially all the bonding in Au+-Ne can be rationalized by physical attraction alone. This is consistent with a natural bond order (NBO) analysis of the Au+-Ne ab initio wavefunctions, which shows the charge on Au+ to be very close to 1.0. In contrast, similar model potential and NBO analyses show quite clearly that physical interactions alone cannot account for the large bond energy values for the Au+-Kr and Au+-Xe complexes and are consistent with covalent contributions to the Au+-Kr and Au+-Xe interactions. Au+-Ar is seen to lie on the borderline between these two limits. In performing the model potential analyses, high-level ab initio calculations are employed [CCSD(T) energies, extrapolated to the complete basis set limit], to obtain reliable values of Re, De and omegae as input. A comparison of the gold-Xe bond distances in several solid-state Au(I, II and III) oxidation-state complex ions, containing "ligand" Xe atoms, prepared by Seppelt and co-workers, with that of the "free" Au+-Xe gas-phase ion is made, and a discussion of the trends is presented.
    The Journal of Physical Chemistry A 06/2008; 112(18):4209-14. · 2.77 Impact Factor
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    ABSTRACT: We report the results of a (2+1) resonance-enhanced multiphoton ionization (REMPI) study of the E2Sigma+(4ssigma) Rydberg state of NO-Kr. We present an assignment of the two-photon spectrum based on a simulation, and discuss it in the context of previously-reported spectra of NO-Ne and NO-Ar. In addition, we report on spectra in the region of the vNO=1 level of the E, F and H' 4s and 3d Rydberg states of NO-Rg (Rg=Ne-Kr). Since the NO vibrational frequency is affected by electron donation from the rare-gas (Rg) atom to the NO+ core, as well as by the penetration of the Rydberg electron, the fundamental NO-stretch frequency reflects the interactions in the complex. The results indicate that the 4s Rydberg state has a strong interaction between the NO+ core and the Kr atom, as was the case for NO-Ar and NO-Ne. For the 3d Rydberg states, although penetration is not as significant as for the 4s Rydberg states, it does play an important role, with subtle angular effects being notable.
    Physical Chemistry Chemical Physics 02/2008; 10(3):375-9. · 4.20 Impact Factor
  • Physical Chemistry Chemical Physics - PHYS CHEM CHEM PHYS. 01/2008; 10(3).
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    ABSTRACT: The Au-Ar complex is reinvestigated employing resonance-enhanced multiphoton ionization spectroscopy. Spectra are reported, corresponding to the atomic transition Au(6p<--6s). This electronic excitation yields (2)Pi and (2)Sigma(+) states of Au-Ar, which interact under the influence of spin-orbit coupling. The spectra are consistent with strong sigma-pi mixing induced by the large spin-orbit coupling of Au, leading to strong interaction of the two Omega=12 states, which arise from the Ar((1)S(0))+Au((2)P(12,32)) asymptotes, and the consequent formation of a "shelf" on the outer wall of the lowest Omega=12 state. In addition, high-level ab initio calculations are reported on the ground electronic state, X (2)Sigma(+), including extrapolation to the basis set limit.
    The Journal of Chemical Physics 11/2007; 127(20):204308. · 3.12 Impact Factor
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    ABSTRACT: High-level ab initio calculations are performed on the coinage metal cations (Cu+, Ag+, and Au+) interacting with each of the rare gases [Rg (Rg = He to Rn)]. The RCCSD(T) procedure is employed, with basis sets being of approximately quintuple-ζ quality, but with the heavier species using relativistic effective core potentials. The interaction potentials are compared to experimental and theoretical data where they exist. In addition, transport coefficients for the mobility and diffusion of the cations in the rare gases are calculated. The latter have involved a rewriting of some of the programs used, and the required modifications are discussed. The mobility results indicate that, rather than being a rare occurrence, mobility minima may be common phenomena. Finally, a new estimate is put forward for the validity of zero-field mobilities in ion mobility spectrometry.
    The Journal of Chemical Physics 10/2007; 127(15):154309-154309-10. · 3.12 Impact Factor
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    ABSTRACT: Zero electron kinetic energy (ZEKE) spectroscopy is employed to gain information on the vibrational energy levels of the para-fluorotoluene (pFT) cation. Vibrationally resolved spectra are obtained following excitation through a range of intermediate vibrational energy levels in the S1 state. These spectra allow the observation of different cationic vibrational modes, whose assignment is achieved both from a knowledge of the S1 vibrational states and also by comparison with density functional calculations. In one notable case, clean ZEKE spectra were obtained from two overlapped S1 features. From the authors' data, the adiabatic ionization energy of pFT was derived as 70,946+/-4 cm(-1). The information on the cationic energy levels obtained will be useful in untangling the intramolecular vibrational redistribution dynamics of pFT in the S1 state.
    The Journal of Chemical Physics 07/2007; 126(24):244304. · 3.12 Impact Factor
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    ABSTRACT: We investigate the A∼2Σ+ state of NO–Ne by high-level ab initio methods, and by (1 + 1) resonance-enhanced multiphoton ionization spectroscopy (REMPI). Despite being able to obtain high-quality spectra of NO–Ar, NO–Kr and NO–Xe, no spectrum of NO–Ne was observed. It is shown that this state is very weakly bound; and that the overlap between the zero-point vibrational energy level in the X∼2Π state, and the bound levels of the A∼2Σ+ state is very small: hence the Franck–Condon factors are close to zero. The location of the Ne atom outside the 3s Rydberg orbital is the cause of the observations.
    Chemical Physics Letters 06/2007; 441(s 4–6):181–186. · 2.15 Impact Factor
  • W.H. Breckenridge, Victoria L. Ayles, Timothy G. Wright
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    ABSTRACT: We have applied the model-potential analysis of Breckenridge and co-workers to the Alk+/Rg systems, where Alk is an alkali atom and Rg is a rare-gas atom. Three spectroscopic constants, Re, De and ωe, are employed to obtain the potential, with fitted parameters being the A and b repulsive Born–Mayer potential parameters, and the effective charge on the metal center, Z. From the analysis, it is concluded that all of these systems can be described in physical terms, with the calculated charge on the metal center being very close to 1.00. Interestingly the effective charge on the metal atom from such model-potential calculations is consistently very slightly greater than 1.00. We discuss and investigate several possible sources for this small anomaly, including a minor breakdown of the model at small internuclear separations, where the “lengths” of the induced multipoles become significant compared to the internuclear separation R. Despite this small breakdown, overall the model is remarkably successful in reproducing high-level ab initio curves for the titular complexes over wide ranges of internuclear distances.
    Chemical Physics 01/2007; · 1.96 Impact Factor
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    ABSTRACT: We have employed (2+1) resonance enhanced multiphoton ionization spectroscopy to investigate the 3d and 4s Rydberg states of the NO molecule when bound to the surface of Rgx clusters (Rg = rare gas). We observe that the spectra of the NO–Arx species converge in appearance as x increases, and this is discussed in terms of two Rg atoms interacting with the NO+ core, with other Rg atoms being “outside” the Rydberg orbital. We show that the interaction of each of the Rg atoms with the NO is essentially independent for the NO–Rg2 complexes: both by comparing our spectra for Rydberg states of NO–Rg and NO–Rg2, and from the results of ab initio calculations on NO+–Rg and NO+–Rg2. In addition, we discuss the disappearance of some electronic bands upon complexation in terms of Franck-Condon factors that are very sensitive to the angular coordinate. We relate our results to those of the bulk by comparing to the previously reported electronic spectroscopy of NO in both Rg matrices and He nanodroplets.
    The Journal of Chemical Physics 10/2006; 125(14):144319-144319-8. · 3.12 Impact Factor
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    ABSTRACT: We employ zero-kinetic-energy (ZEKE) photoelectron spectroscopy with nanosecond laser pulses to study intramolecular vibrational redistribution (IVR) in S(1) para-fluorotoluene. The frequency resolution of the probe step is superior to that obtained in any studies on this molecule to date. We focus on the behavior of the 13(1) (C-CH(3) stretch) and 7a(1) (C-F stretch) vibrational states whose dynamics have previously received significant attention, but with contradictory results. We show conclusively that, under our experimental conditions, the 7a(1) vibrational state undergoes significantly more efficient IVR than does the 13(1) state. Indeed, under the experimental conditions used here, the 13(1) state undergoes very little IVR. These two states are especially interesting because their energies are only 36 cm(-1) apart, and the two vibrational modes have the same symmetry. We discuss the role of experimental conditions in observations of IVR in some detail, and thereby suggest explanations for the discrepancies reported to date.
    The Journal of Chemical Physics 10/2006; 125(12):124308. · 3.12 Impact Factor
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    ABSTRACT: We have employed (2+1) resonance-enhanced multiphoton ionization spectroscopy to record electronic absorption spectra of NO-Rg (Rg=Ne,Ar,Kr) van der Waals complexes. The nitric oxide molecule is the chromophore, and the excitation corresponds to an electron being promoted from the 2ppi* orbital to 3dsigma, 3dpi, and 3ddelta Rydberg states. We review the ordering of the 3dlambda states of NO and use this as a basis for discussing the 3d components in the NO-Rg complexes, in terms of the interactions between the Rydberg electron, the core, and the Rg atom. Predissociation of the H' 2Pi state occurs through the F2Delta state for NO-Ar and NO-Kr, and this will be considered. We shall also outline problems encountered when trying to record similar spectra for NO-Xe, related to the presence of atomic Xe resonances.
    The Journal of Chemical Physics 07/2006; 124(21):214302. · 3.12 Impact Factor
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    ABSTRACT: We report (1+1) resonance-enhanced multiphoton ionization spectra for clusters of para-fluorotoluene (pFT)n (n=1–11). After n=2, the spectra appear to have converged in appearance, suggestive of a dimer chromophore, with weak bonding for subsequent additions of pFT molecules. The spectra also indicate dramatic, vibrational-mode-sensitive changes of oscillator strength between the monomer and the clusters. We also briefly describe the results of probing different parts of the expansion, and varying the laser power.
    Chemical Physics 01/2006; 430(4):282-286. · 1.96 Impact Factor