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Ian D. Hands

Other affiliations: University of East Anglia
Bio: Ian D. Hands is an academic researcher from University of Nottingham. The author has contributed to research in topics: Vibronic coupling & Jahn–Teller effect. The author has an hindex of 10, co-authored 33 publications receiving 245 citations. Previous affiliations of Ian D. Hands include University of East Anglia.

Papers
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Journal ArticleDOI
TL;DR: In this article, it was shown that neglect of quadratic coupling in previous models for C60- ions results in a significant overestimate of the linear coupling constants, which can be used to make a coherent interpretation to be made of earlier experimental and theoretical results which at first sight are incompatible.
Abstract: Electron-phonon coupling is an important factor in understanding many properties of the C60 fullerides. However, there has been little success in quantifying the strength of the vibronic coupling in C60 ions, with considerable disagreement between experimental and theoretical results. We will show that neglect of quadratic coupling in previous models for C60- ions results in a significant overestimate of the linear coupling constants. Including quadratic coupling allows a coherent interpretation to be made of earlier experimental and theoretical results which at first sight are incompatible.

29 citations

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TL;DR: Using Huckel molecular-orbital theory, images are created to represent the electron distributions expected for a C60 molecule adsorbed on a substrate as mentioned in this paper. But the effect of the interaction of the molecule with the substrate is treated purely from the basis of symmetry using group theoretical methods, and it is found that the more complicated ab initio methods usually employed to simulate STM images are not required in order to match observed results.
Abstract: Using Huckel molecular-orbital theory, images are created to represent the electron distributions expected for a C60 molecule adsorbed on a substrate. Three different orientations of the C60 molecule on the substrate are considered. The effect of the interaction of the molecule with the substrate is treated purely from the basis of symmetry using group theoretical methods. The resulting electron distributions are then used to generate idealized images which represent how the molecule may appear when observed in a scanning tunneling microscope (STM) experiment. Comparison is made with STM images appearing in the literature. It is found that the more complicated ab initio methods usually employed to simulate STM images are not required in order to match observed results. Furthermore, we find that an unequivocal identification of the orbitals responsible for a given STM image cannot be made from analysis of the STM image alone.

22 citations

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TL;DR: In this paper, the effect of Jahn-Teller (JT) distortions on ion imaging using scanning tunneling microscopy (STM) has been investigated using Huckel molecular-orbital theory.
Abstract: Adsorption of ${\text{C}}_{60}$ on a metallic surface may be expected to result in electronic charge transfer to the organic adsorbant, even if a buffer layer is included between the ${\text{C}}_{60}$ molecules and substrate. Subsequently, intramolecular coupling between the molecule's electronic and vibrational degrees of freedom would be expected to result in species subject to Jahn-Teller (JT) distortions. In this work, we use H\"uckel molecular-orbital theory to visualize the effect that JT interactions may have on ${\text{C}}_{60}^{\ensuremath{-}}$ ions imaged using scanning tunneling microscopy (STM). Several distortion symmetries and adsorption orientations are considered and the resulting simulations are compared to STM images in the literature.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the ultrafast decay rates of photoexcited C 60 -and C 60 2 - ions have been measured in the condensed phase, and a bottleneck in the ground state recovery has also been detected, and its interpretation is discussed.

16 citations

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TL;DR: In this article, the optically induced generation of second harmonics in isotropic media, which arises through a six-wave mixing interaction, is employed in ultrafast studies of orientational relaxation in solution.
Abstract: The optically induced generation of second harmonics in isotropic media, which arises through a six-wave mixing interaction, is employed in ultrafast studies of orientational relaxation in solution...

14 citations


Cited by
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Journal ArticleDOI
25 Feb 2016-Nature
TL;DR: By exciting metallic K3C60 with mid-infrared optical pulses, a large increase in carrier mobility is induced, accompanied by the opening of a gap in the optical conductivity, which is observed at equilibrium when cooling metallic K 3C60 below Tc (20 kelvin).
Abstract: The use of light to control the properties of condensed-matter materials is a promising area of research, with the long-term prospect that it might lead to the development of quantum devices driven by light. In particular, it was shown recently that nonlinear excitation of certain phonons in bilayer copper oxides induces superconducting-like optical properties at temperatures far above the material's superconducting transition temperature (Tc). This effect was accompanied by the disruption of competing charge-density-wave correlations, explaining some, but not all, of the experimental results. Andrea Cavalleri and colleagues now report that by exciting metallic K3C60 with mid-infrared optical pulses, they can induce a large increase in carrier mobility, accompanied by the opening of a gap in the optical conductivity. Strikingly, these same signatures are observed at equilibrium when K3C60 cools below its Tc of 20 K.

466 citations

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TL;DR: Reactions discussed include intra- and intermolecular electron- and proton-transfer processes, as well as photochromic reactions occurring with and without bond breaking or bond formation, namely ring-opening reactions and cis-trans isomerizations, respectively.
Abstract: Ultrafast photochemical reactions in liquids occur on similar or shorter time scales compared to the equilibration of the optically populated excited state. This equilibration involves the relaxation of intramolecular and/or solvent modes. As a consequence, the reaction dynamics are no longer exponential, cannot be quantified by rate constants, and may depend on the excitation wavelength contrary to slower photochemical processes occurring from equilibrated excited states. Such ultrafast photoinduced reactions do no longer obey the Kasha–Vavilov rule. Nonequilibrium effects are also observed in diffusion-controlled intermolecular processes directly after photoexcitation, and their proper description gives access to the intrinsic reaction dynamics that are normally hidden by diffusion. Here we discuss these topics in relation to ultrafast organic photochemical reactions in homogeneous liquids. Discussed reactions include intra- and intermolecular electron- and proton-transfer processes, as well as photochr...

292 citations

Journal ArticleDOI
18 May 2015-Nature
TL;DR: In this article, coherent optical excitation of molecular vibrations in the organic conductor K3C60 can induce a non-equilibrium state with the optical properties of a superconductor, and a transient gap in the real part of the optical conductivity and a low-frequency divergence of the imaginary part are measured for base temperatures far above equilibrium Tc=20 K.
Abstract: The control of non-equilibrium phenomena in complex solids is an important research frontier, encompassing new effects like light induced superconductivity. Here, we show that coherent optical excitation of molecular vibrations in the organic conductor K3C60 can induce a non-equilibrium state with the optical properties of a superconductor. A transient gap in the real part of the optical conductivity and a low-frequency divergence of the imaginary part are measured for base temperatures far above equilibrium Tc=20 K. These findings underscore the role of coherent light fields in inducing emergent order.

274 citations

Journal ArticleDOI
TL;DR: The ultrafast optically-heterodyne-detected optical Kerr effect (OHD-OKE) is a relatively simple tool for recording the ultrafast dynamics of liquids with high temporal resolution and excellent signal-to-noise ratios.
Abstract: The ultrafast optically-heterodyne-detected optical Kerr effect (OHD-OKE) is established as a relatively simple tool for recording the ultrafast dynamics of liquids with high temporal resolution and excellent signal-to-noise ratios. The principles and practice of the OHD-OKE method are outlined. Its application in recording the dynamics of several molecular liquids is described. The data are discussed in terms of the underlying microscopic molecular motions. Orientational motion--both librational and diffusive--is responsible for a significant fraction of the dynamics. Other potential contributions are discussed, but these are less readily assigned. The application of OHD-OKE measurements in interpreting ultrafast studies of the optical dynamics of solutions is discussed. Finally the extension of OHD-OKE methods to record the dynamics of more complex, heterogeneous, media is described.

197 citations

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TL;DR: This work indicates that the off-electronic resonance SFG technique is sensitive enough to collect chiral SFG vibrational spectra of interfacial proteins and peptides, providing more structural information to elucidate interfacial protein and peptide structures.
Abstract: In this work, we demonstrate the feasibility to collect off-electronic resonance chiral sum frequency generation (SFG) vibrational spectra from interfacial proteins and peptides at the solid/liquid interface in situ. It is difficult to directly detect a chiral SFG vibrational spectrum from interfacial fibrinogen molecules. By adopting an interference enhancement method, such a chiral SFG vibrational spectrum can be deduced from interference spectra between the normal achiral spectrum and the chiral spectrum. We found that the chiral SFG vibrational spectrum of interfacial fibrinogen was mainly contributed by the β-sheet structure. For a β-sheet peptide tachyplesin I, which may be quite ordered at the solid/liquid interface, chiral SFG vibrational spectra can be collected directly. We believe that these chiral signals are mainly contributed by electric dipole contributions, which can dominate the chiroptical responses of uniaxial systems. For the first time, to our knowledge, this work indicates that the off-electronic resonance SFG technique is sensitive enough to collect chiral SFG vibrational spectra of interfacial proteins and peptides, providing more structural information to elucidate interfacial protein and peptide structures.

183 citations