Carolyn D Withers

University of Nottingham, Nottingham, ENG, United Kingdom

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Publications (8)22.57 Total impact

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    ABSTRACT: The intramolecular vibrational redistribution (IVR) dynamics following the excitation of a mode in the first electronically excited states of toluene, toluene-d3 and p-fluorotoluene that has predominantly C-CH3 stretching character and an internal energy of ∼1200 cm(-1) have been compared using picosecond time-resolved photoelectron imaging spectroscopy as a probe. Temporal changes in the intensities of spectral features in each molecule have enabled IVR lifetimes of 12, 15 and 50 ps, respectively, to be determined. Our measurements show that doorway states are critical in mediating the IVR dynamics in toluene and toluene-d3, and we deduce that these doorway states, which are assigned in the course of this work, are also instrumental in reducing the IVR lifetimes of these molecules relative to p-fluorotoluene.
    Physical Chemistry Chemical Physics 09/2013; · 3.83 Impact Factor
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    ABSTRACT: We present a systematic investigation of the accuracy of the various theories and basis sets that can be applied to study the interaction of Cl− ions with Ar atoms. It is conclusively shown that gaseous ion mobility can distinguish among theoretical ion-neutral interaction potentials. Based on the conclusions, high-level ab initio potential energy curves are obtained for all of the Cl−–RG (RG = He–Rn) complexes. Spectroscopic constants have been derived from these potentials and are compared to a range of theoretical and experimental data, to which they generally show good agreement. General trends are discussed in comparison to other halogen-rare gas complexes previously studied. The potentials also have been tested by using them to calculate transport coefficients for Cl− moving through a bath of RG atoms.
    The Journal of Chemical Physics 07/2011; 135(2):024312-024312-11. · 3.12 Impact Factor
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    ABSTRACT: Electronic spectra of the Au-Ne complex have been recorded for the first time in the vicinity of the atomic Au 6p ← 6s transition. A structured spectrum was observed near the Au ^2P3/2 ← ^2S1/2 transition, however, the complex spectrum expected near the Au ^2P1/2 ← ^2S1/2 transition was not observed. This is rationalized using high level ab intio calculations. R. J. Plowright, A. M. Gardner, C. D. Withers, T. G. Wright, M. D. Morse and W. H. Breckenridge, J. Phys. Chem. A, 114, 3103, (2010)
    06/2011;
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    ABSTRACT: We present high level ab initio potential energy curves for the M(n+)-RG complexes, where n = 1, 2, RG = rare gas, and M = Be and Mg. Spectroscopic constants have been derived from these potentials, and they generally show very good agreement with the available experimental data. The potentials have also been employed in calculating transport coefficients for M(+) moving through a bath of RG atoms, and the isotopic scaling relationship is examined for Mg(+) in Ne. Trends in binding energies, D(e), and bond lengths, R(e), are discussed and compared to similar ab initio results involving the corresponding complexes of the heavier alkaline earth metal ions. We identify some very unusual behavior, particularly for Be(+)-Ne, and offer possible explanations.
    The Journal of Physical Chemistry A 07/2010; 114(28):7631-41. · 2.77 Impact Factor
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    ABSTRACT: We report electronic spectra of the Au-Ne complex, obtained in the vicinity of the Au atomic 6p <-- 6s transition. The structured spectrum found near the (2)P(3/2) <-- (2)S(1/2) transition is analyzed. We also explain the nonobservance of a spectrum close to the 6(2)P(1/2) state, using the results of high level ab initio calculations and insight from previous work on other Au-RG complexes (where RG = Ar, Kr, and Xe). Basis set extrapolated RCCSD(T) potential energy curves are also presented for the X(2)Sigma(+) ground state of Au-Ne, and the derived D(e) value is compared to experimental values. We then present an overview of trends through the Au-RG series: included in this are calculations on the X states of Au-He and Au-Rn, as well as for Au(+)-He. We also report further calculations on the states which arise from the interaction of Au(6(2)P(J)) with the rare gas atoms and include a Franck-Condon simulation of the D(2)Pi(3/2) <-- X(2)Sigma(1/2)(+) transition for Au-Ar. Trends in the spectroscopy across this series are summarized, and the Hund's case (a)/(c) character discussed.
    The Journal of Physical Chemistry A 03/2010; 114(9):3103-13. · 2.77 Impact Factor
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    ABSTRACT: We present high level ab initio potential energy curves for the M(n+)-RG complexes, where n=1 and 2; RG=He-Rn; and M=Ca, Sr, and Ra. Spectroscopic constants have been derived from these potentials and are compared with a wide range of experimental and previous theoretical data, and good agreement is generally seen. Large changes in binding energy, D(e), and bond length, R(e), between M(+)-He, M(+)-Ne, and M(+)-Ar, also found previously in the analogous Ba(+)-RG complexes [M. F. McGuirk et al., J. Chem. Phys. 130, 194305 (2009)], are identified and the cause investigated; the results shed light on the previous Ba(+)-RG results. These unusual trends are not observed for the dicationic complexes, which behave in a fashion similar to the isoelectronic alkali metal ion complexes. The potentials have also been employed to calculate transport coefficients for M(n+) moving through a bath of rare gas (RG) atoms.
    The Journal of Chemical Physics 02/2010; 132(5):054302. · 3.12 Impact Factor
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    ABSTRACT: We present high-level ab initio potential energy curves for barium cations and dications interacting with RG atoms (RG = rare gas). These potentials are employed to derive spectroscopic parameters for the Ba+–RG and Ba2+–RG complexes, and also to derive the transport coefficients for Ba+ and Ba2+ moving through a bath of the rare gas. The results are compared to the limited experimental data, which generally show reasonable agreement. We identify a large change in binding energy going from Ba+–He and Ba+–Ne to Ba+–Ar, which is not present in Ba2+–RG, and show that this is due to significant dispersion interactions in Ba+–RG.
    The Journal of Chemical Physics 05/2009; 130(19):194305-194305-9. · 3.12 Impact Factor
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    ABSTRACT: We report electronic spectra of the Au-Xe complex for the first time. The transitions are recorded in the vicinity of the Au atomic 6p<-- 6s transitions. Structured spectra are found close to both the 6(2)P(1/2) and 6(2)P(3/2) states. The former is assigned as a (2)Pi(1/2) state in line with previous work on Au-Ar and Au-Kr; the possible assignment of the second spectrum is discussed. In addition, a large basis set extrapolated RCCSD(T) potential energy curve for the ground state, X(2)Sigma(+), is presented and derived spectroscopic parameters reported. More qualitative calculations are presented for electronically-excited states which arise from the Au(5(2)D) + Xe and Au(6(2)P) + Xe asymptotes, as well as some higher-lying states. The ab initio results are employed in the assignment of the reported spectra.
    Physical Chemistry Chemical Physics 04/2009; 11(10):1539-50. · 3.83 Impact Factor