Author: P. N. Sanda
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
We report the first ultrahigh vacuum study of surface enhanced Raman scattering from pyridine adsorbed on a clean well-defined single-crystal silver surface. The surface contains a smooth modulation (1 micron periodicity) to allow optical coupling to surface plasmon polaritons. A large mode-selective enhancement of the Raman signal from the first monolayer is observed at surface plasmon polariton resonance. (Author).
Author: Richard Chang
Publisher: Springer Science & Business Media
ISBN: 1461592577
Category : Science
Languages : en
Pages : 424
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Book Description
In the course of the development of surface science, advances have been identified with the introduction of new diagnostic probes for analytical characterization of the adsorbates and microscopic structure of surfaces and interfaces. Among the most recently de veloped techniques, and one around which a storm of controversy has developed, is what has now been earmarked as surface enhanced Raman scattering (SERS). Within this phenomenon, molecules adsorbed onto metal surfaces under certain conditions exhibit an anomalously large interaction cross section for the Raman effect. This makes it possible to observe the detailed vibrational signature of the adsorbate in the ambient phase with an energy resolution much higher than that which is presently available in electron energy loss spectroscopy and when the surface is in contact with a much larger amount of material than that which can be tolerated in infrared absorption experiments. The ability to perform vibrational spectroscopy under these conditions would lead to a new understanding about the chemical identity, geome try, and bonding of adsorbed material at a level previously unacces sible. It is for these reasons that the last few years have brought an explosion of activity surrounding the exploitation of SERS. The search for the origines) of the anomalous enhancement has given rise to a research sub-activity of its own. Efforts to explain the en hancement have led to an increased understanding of the whole range of phenomena associated with the interaction of photons with adsor bates and metal surfaces.
Author: J. E. Demuth
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
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Book Description
High resolution electron energy loss (EELS), UV photoemission, (UPS), low energy electron diffraction (LEED), Auger electron, and thermal desorption spectroscopic techniques have been applied to characterize the bonding, molecular orientation and vibrations of pyridine and benzene on clean Ag(111). These results are used to interpret the surface enhanced Raman spectra of these molecules adsorbed on a clean, well-defined single crystal Ag(111) surface containing a smooth periodic modulation (1 micron wavelength, approx. 500 A amplitude) which permits optical coupling to surface plasmons-polaritons. We observe enhanced Raman scattering (RS) for chemisorbed species only when we are at appropriate incidence angles so as to excite surface plasmons. Coverage-dependent RS studies indicate a long-range field enhancement of approx. 100 for physisorbed layers and a mode-selective, short-range enhancement of approx 10,000 for the symmetric ring breathing mode of pyridine. This short-range enhancement only occurs for pyridine coverages slightly above 3 x 10 to the 14th power molecules/sq cm where changes in the UPS spectra and our UPS derived uptake-rates are also observed. Similar coverage-dependent effects are also observed in UPS and EELS for chemisorbed pyridine on the ideal Ag(111) surface. These as well as LEED results showing the modulated surface to be predominately (approx. 90%) single crystal Ag(111), encourage us to directly compare the results obtained for the two surfaces.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 1368
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Book Description
Author: Milton Kerker
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 728
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Book Description
Author: Pia Naoko Sanda
Publisher:
ISBN:
Category : Raman effect, Surface enhanced
Languages : en
Pages : 300
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Book Description
Author: I. Pockrand
Publisher: Springer
ISBN: 3540389520
Category : Science
Languages : en
Pages : 172
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Book Description
Author: Theodore E. Madey
Publisher: Springer Science & Business Media
ISBN: 1468487590
Category : Science
Languages : en
Pages : 478
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Book Description
The observation of the vibrational spectra of adsorbed species provides one of the most incisive methods for und erst an ding chemical and physical phenomena on surfaces. At the present time, many approaches may be applied to studies of molecular vibrations on surfaces. Some of these are used on high-area solids of technological importance (e.g., heterogeneous catalysts) while others are applied to single-crystal substrates to gain better understanding under conditions of controlled surface structure. This book has attempted to bring together in one place a discussion of the major methods used to measure vibrational spectra of surface species. The emphasis is on basic concepts and experimental methods rather than a current survey of the extensive literature in this field. Two introductory chapters describe the basic theoretical aspects of vibrational spectroscopy on surfaces, dealing with normal modes and excitation mechanisms in vibrational spectroscopy. The remaining seven chapters deal with various methods employed to observe surface vibra tions. These are arranged in an order that first treats the use of various methods on surfaces that are not of the single-crystal type. It is in this area that the field first got started in the late 1940s with pioneering work by Terenin and others in the Soviet Union, and by Eisehens and others in the United States in the 1950s. The last four chapters deal with relatively recent methods that permit vibrational studies to be made on single crystal substrates.
Author: Uemit Ertuerk
Publisher:
ISBN:
Category :
Languages : en
Pages : 76
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Book Description
Author: R. Caudano
Publisher: Springer Science & Business Media
ISBN: 1468440586
Category : Science
Languages : en
Pages : 570
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Book Description
This volume contains most of the invited and contributed papers presented at the second international conference devoted to the general topic "Vibrations at Surfaces" and which took place from 10 to 12 September 1980 at the Facu1tes Notre-Dame de 1a Paix in Namur, Belgium. The conference was organized to review the large amount of information gathered in this field over the late seventies as a result of th~ rapid improvements and dissemination of surface spectroscopic technique such a electron energy loss, infrared and Raman surface spectroscopies. Much time was devoted to Raman spectroscopy of adsorbed mo1e 'cu1es. After several years of vivid debate over the causes of the observed large enhancement of Raman cross section, a clearer pic ture emerges from the papers presented here: the actual value of the enhancement factor does depend in a complicated manner on long range surface roughness, atomic-scale roughness and the dielectric properties of the substrate as well as on the electronic structure of the molecule in its adsorbed state. Less controversial are the results obtained with electron energy loss spectroscopy (EELS) and several sessions of the con ference were devoted to the approach. As witnessed by the growing number of laboratories using the technique, EELS is now a mature spectroscopic tool for the characterization and analysis of the chemisorption bond.
