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The adsorption of water on Pt(111) studied by irreflection and UV-photoemission spectroscopy
A442 162
Surface Science 147 (1984) 162 178 North-Holland, Amsterdam
GENERAL A S P E C T S O F B E A M T H R E S H O L D C. G A U B E R T ,
R. B A U D O I N G
EFFECTS
IN
LEED
and Y. GAUTH IE R
Groupe d'Etude des Surfaces, Laboratoire de SpeetromOtrie Physique (associ~ a'u CNRSI, Unit er~ltb Seientifique et MOdicale de Grenoble, BP 68, F-38402 Saint- Martin- d'HOres, France and J. R U N D G R E N
Department of Theoretical Physics, The Royal lnstttute of Technolog3', S- 100- 44 Stockholm, Sweden Received 29 November 1983; accepted for publication 2 July 1984 We present in this paper some general aspects of beam threshold effects in LEED concerning their observation, their extension and their detection. The observation is possible on LEED intensities but also on crystal to ground current and total reflected current. We discuss the various types of profiles due to threshold effects for LEED intensities. From universal relations coming from emergence conditions of a new beam we draw universal charts for the "speed of emergence" versus E, O or ,~. These charts are used for a discussion of the range in I ( E ) or 1(~) profiles, where threshold effects may affect the LEED intensities. The same relations are used for a discussion of the detection of threshold effects. Assuming a Gaussian distribution (in energy and angles) for the incident beam, we derive a "total equivalent experimental resolution" and we discuss the consequence on intensity profiles and on the optimal conditions of detection.
Surface Science 147 (19841 179-190 North-Holland, Amsterdam
179
THE A D S O R P T I O N OF WATER ON P t ( l l l ) S T U D I E D BY IRREFLECTION A N D U V - P H O T O E M I S S I O N S P E C T R O S C O P Y E. L A N G E N B A C H ,
A. SPITZER
and H. LOTH
2. Ph3sikalisches Institut der Rheinisch-Westfdlischen Teehnischen Ilochschule Aachen, D-5100 Aachen, Fed. Rep. of Germany Received 10 May 1984: accepted for publication 18 July 1984
IR-reflection spectroscopy (IRS) under grazing incidence and UV-photoemission (UPS) with Hel and Hell radiation were used to study the adsorption of D20 and H20, respectively, on Pt(111) under U HV conditions. In I RS three different vibrational bands in the OD stretch region yield information about the orientation of hydrogen-bonded water molecules and the formation of water clusters. Initially formed water multimers grow to clusters and finally build up multilayers. From UPS the adsorption of molecular water in the whole coverage range is confirmed. Both UPS and IRS show that the water molecules in the "first layer" are bound through their oxygen end to the surface.
Surface Science 147 (1984) 162 178 North-Holland, Amsterdam
GENERAL A S P E C T S O F B E A M T H R E S H O L D C. G A U B E R T ,
R. B A U D O I N G
EFFECTS
IN
LEED
and Y. GAUTH IE R
Groupe d'Etude des Surfaces, Laboratoire de SpeetromOtrie Physique (associ~ a'u CNRSI, Unit er~ltb Seientifique et MOdicale de Grenoble, BP 68, F-38402 Saint- Martin- d'HOres, France and J. R U N D G R E N
Department of Theoretical Physics, The Royal lnstttute of Technolog3', S- 100- 44 Stockholm, Sweden Received 29 November 1983; accepted for publication 2 July 1984 We present in this paper some general aspects of beam threshold effects in LEED concerning their observation, their extension and their detection. The observation is possible on LEED intensities but also on crystal to ground current and total reflected current. We discuss the various types of profiles due to threshold effects for LEED intensities. From universal relations coming from emergence conditions of a new beam we draw universal charts for the "speed of emergence" versus E, O or ,~. These charts are used for a discussion of the range in I ( E ) or 1(~) profiles, where threshold effects may affect the LEED intensities. The same relations are used for a discussion of the detection of threshold effects. Assuming a Gaussian distribution (in energy and angles) for the incident beam, we derive a "total equivalent experimental resolution" and we discuss the consequence on intensity profiles and on the optimal conditions of detection.
Surface Science 147 (19841 179-190 North-Holland, Amsterdam
179
THE A D S O R P T I O N OF WATER ON P t ( l l l ) S T U D I E D BY IRREFLECTION A N D U V - P H O T O E M I S S I O N S P E C T R O S C O P Y E. L A N G E N B A C H ,
A. SPITZER
and H. LOTH
2. Ph3sikalisches Institut der Rheinisch-Westfdlischen Teehnischen Ilochschule Aachen, D-5100 Aachen, Fed. Rep. of Germany Received 10 May 1984: accepted for publication 18 July 1984
IR-reflection spectroscopy (IRS) under grazing incidence and UV-photoemission (UPS) with Hel and Hell radiation were used to study the adsorption of D20 and H20, respectively, on Pt(111) under U HV conditions. In I RS three different vibrational bands in the OD stretch region yield information about the orientation of hydrogen-bonded water molecules and the formation of water clusters. Initially formed water multimers grow to clusters and finally build up multilayers. From UPS the adsorption of molecular water in the whole coverage range is confirmed. Both UPS and IRS show that the water molecules in the "first layer" are bound through their oxygen end to the surface.