Mark Surman

The influence of high intensity terahertz radiation on mammalian cell adhesion, proliferation and differentiation.

Understanding the influence of exposure of biological systems to THz radiation is becoming increasingly important. There is some evidence to suggest that THz radiation can influence important activities within mammalian cells. This study evaluated the influence of the high peak power, low average power THz radiation produced by the ALICE (Daresbury Laboratory, UK) synchrotron source on human epithelial and embryonic stem cells. The cells were maintained under standard tissue culture conditions, during which the THz radiation was delivered directly into the incubator for various exposure times. The influence of the THz radiation on cell morphology, attachment, proliferation and differentiation was evaluated. The study demonstrated that there was no difference in any of these parameters between irradiated and control cell cultures. It is suggested that under these conditions the cells are capable of compensating for any effects caused by exposure to THz radiation with the peak powers levels employed in these studies.

Investigation of the CO induced lifting of the (1×2) reconstruction on Pt{1 1 0} using synchrotron far-infrared RAIRS

We present a study of the coverage and temperature dependence of the Pt–CO stretching vibration of CO adsorbed on both the reconstructed Pt{1 1 0}-(1×2) and the unreconstructed Pt{1 1 0}-(1×1) surfaces. The metal–carbon stretching vibration is shown to be a sensitive probe of the structure of the underlying Pt{1 1 0} surface. As a function of coverage, the position of the adsorption peak shifts from 471 to 480 cm?1 at 310 K, accompanying the adsorbate induced lifting of the reconstruction. At 115 K, where the reconstruction is not lifted, the absorption band remains centered at 466 cm?1, however the FWHM increases from 6 cm?1 at 0.05 L to 15 cm?1 at saturation. The band at 466 cm?1 is attributed to initial adsorption into atop sites on the atomic ridges followed by adsorption into atop sites on the (1 1 1) microfacets. The sensitivity of the synchrotron far-infrared RAIRS technique has allowed the lifting of the reconstruction to be followed as a function of temperature and, for the first time, allowed detection of localised lifting of the (1×2) reconstruction at a temperature 50 K lower than previously reported.

Adsorption of CO on Pt{1 1 1}: a synchrotron far-infrared RAIRS study

Synchrotron far-IR light has allowed the rapid collection of high quality reflection-absorption infrared spectra of the metal-adsorbate stretching vibrations of CO adsorbed in atop (464 cm(-1)) and bridging (3 76 cm(-1)) sites on Pt{1 1 1} at half monolayer coverage at 260 K. In contrast to earlier reports we find no evidence for a Fermi resonance induced splitting of the absorption band assigned to the bridge bonded species.

'Near-field optical microscopy with an infra-red free electron laser applied to cancer diagnosis'

We show that the combination of a scanning near field optical microscope and an infra-red free electron laser yields chemical images with sub-cellular spatial resolution that have the potential to provide a diagnostic for oesophageal adenocarcinoma.

The origin of inverse absorption bands observed in the far-infrared RAIRS spectra of SnCl4 and SnBr4 adsorbed on thin-film SnO2 surfaces

The adsorption of SnCl4 and SnBr4 on polycrystalline SnO2 has been studied using synchrotron radiation based far-infrared reflection absorption infrared spectroscopy FIR-RAIRS. In order to exploit the sensitivity advantages of the buried metal layer method, the SnO2 is in the form of a thin film deposited on a tungsten foil substrate. Adsorption of SnCl4 and SnBr4 on an oxygen sputtered surface at 120 K results in spectra characteristic of condensed multilayers. In addition, both spectra exhibit an inverse absorption band centred at 355 cm(-1). Modified 4-layer, wavelength-dependent, Greenler calculations show that this inverse absorption band is induced by the presence of the adsorbate but is characteristic of the SnO2 layer. The lack of any frequency shift upon changing the adsorbate from SnCl4 to SnBr4 rules out the possibility that the inverse absorption band is due to a dipole-forbidden parallel mode of the molecule excited via the interaction with free electron oscillations in the metal, resulting from the radiation induced oscillating electric field just below the surface

A far-infrared RAIRS investigation of SnCl4 and water on thin-film carbon and silica surfaces

Far-infrared RAIRS spectroscopy employing synchrotron radiation as a soul ee, has been used to study the interaction of SnCl4, and water on thin-him silica and carbon surfaces. This has been made possible by growing the thin films on a highly reflecting tungsten substrate, enabling the conventional RAIRS geometry to be used. In addition to the observation of a strongly chemisorbed species on the silica surface the spectra from both surfaces indicate the presence of a more weakly bound complex containing both water and SnCl4

A far-infrared RAIRS investigation of SnCl4 on a silica surface using the buried metal layer approach

Far-infra red RAIRS spectroscopy employing synchrotron radiation as a source, has been used to study the interaction of SnCl4 on a thin-him silica surface. This has been made possible by growing the silica film on a highly reflecting tungsten substrate, enabling the conventional RAIRS geometry to be used. We show that reasonable S/N RAIRS spectra can be obtained in this region, even from films up to 1000 thick, enabling subtle details in the spectrum of the chemisorbed species to be obtained

Anomalous inverse absorption features in the far-infrared RAIRS spectra of SnCl4 on thin-film SnO2 surfaces

As part of a study of the chemistry of tin oxide chemical vapor deposition precursors at oxide surfaces, we have utilized the so-called buried metal layer approach to obtain far-IR reflection absorption infrared spectroscopy (RAIRS) spectra for SnCl4 adsorbed at a tin oxide surface supported on a polycrystalline tungsten foil. Two types of surface preparation—namely, sputtering with Ar or O2—have been used to clean the tin oxide surfaces prior to experiment. On O2-sputtered surfaces at 300 K, the spectra are dominated by an inverse-absorption feature in the form of a positive-going band in the spectrum, obtained via the ratio of the sample spectrum to that of the clean surface background. At low temperature, the spectra display both the positive-going inverse-absorption feature and the normal negative-going absorption features common to many RAIRS studies from metallic surfaces. On an Ar-sputtered surface, the inverse absorption band is not observed, but is replaced, at least at 300 K, by an absorption ba...

Spin magnetic moments from angle resolved magnetic circular dichroism in resonant photoemission decay

Abstract Measurement of the resonant photoelectrons at the photon energy of the absorption edge gives a powerful extension of magnetic circular x-ray dichroism (MCXD). Because each type of core hole produced in absorption emits electrons in different directions decaying to different final states we can obtain more detailed information on the core hole produced by the absorption step and this gives improved knowledge of the original valence shell polarization. This can be used to tell apart the spin magnetic moment and magnetic dipole term.

Long-range ferromagnetic order of Ni - O overlayers studied by quadrupolar resonant photoemission

The resonant photoemission decay from the Ni 2p x-ray absorption of ferromagnetic nickel can be decomposed into contributions from the monopole and the quadrupole moment of the core hole with substantially different signals for each of the final-state LS-terms. The quadrupole moment induces an anisotropic contribution to the photoelectron distribution which can be used to identify the different final-state configurations in Ni and to separate substrate and overlayer signals on the Ni(110) - () O surface. The results provide evidence for a long-range ferromagnetic ordering in the Ni - O overlayer.