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Water adsorption on the NaCl surface
A21 1 adsorption. Transition to the underlayer adsorption state is an activated process and in terms of energetics seems to be less likely. For nitrogen or carbon, a hollow site under the iron atom is the preferential site; the transition to such an adsorption state from the adsorption on the non-reconstructed surface requires no activation. On the basis of LEED measurements and the results obtained, sphere models are suggested for two-dimensional structures of iron (111) surfaces with oxygen, nitrogen or carbon adsorbed on them.
Surface Science 247 (1991) 269 273 North-Holland
269
Water adsorption on the NaC1 surface S. F~31sch and M. Henzler lnstitut ]'fir Festk6rperphysik, Appelstrasse 2, W-3000 Hannover, Germany Received 21 May 1990; accepted for publication 7 September 1990 H 2 0 adsorption on epitaxial NaCI films has been investigated by UPS, XPS and EELS, focused on the dependence of the adsorption behaviour on the defect-structure of the substrate. On the smooth, homogeneous surface only molecular adsorption is observed. A three-dimensional ice-layer grows at a deposition temperature of 130 K. After desorption of the H 2 0 layer (145 K at 1 )< 10 -6 Pa partial H 2 0 pressure) a small a m o u n t of H 2 0 molecules remains on the surface in a modified state of bonding. Surface color centers produced by electron b o m b a r d m e n t however induce chemisorption. These defects act as reactive sites which cause dissociation and OH production.
274
Atom ion transition energies for alkali atoms
Surface Science 247 (1991) 274-278 North-Holland
on
a tungsten surface
Longin Gladyszewski and Grzegorz Gladyszewski Institute of Physics, Maria Curie-Sktodowska Unioersity, 20-031 Lublin, Poland Received 21 May 1990; accepted for publication 20 August 1990 lon Qi and atom Qa desorption energies for five alkali metals on tungsten were determined using the ion thermal emission noise method. We present the results of calculations of the activation energy E for the charge transfer process on the tungsten surface. A special energetic balance equation for determining E is used: (Qa - Qi) + e ( V - ~) + E = 0; (V is the ionization potential).
Surface Science 247 (1991) 279-283 North-Holland
279
Coadsorption of beryllium and potassium on a (112) tungsten plane Z. Dworecki Institute of Physics, Pedagogical Unioersity, Oleska 48, 45-052 Opole, Poland Received 21 May 1990; accepted for publication 19 September 1990 The adsorption and coadsorption of beryllium and potassium on the tungsten (112) plane was studied using a probe-hole field electron microscope (FEM). Measurements were made at 78 K for potassium and at 300 K for beryllium. It has been found that the adsorption of potassium decreases and that of beryllium increases the work-function of the (112) W plane. At small coverages with potassium atoms (O K < 0.2) on the (112) W plane succesive evaporation of beryllium atoms causes a decrease of the work-function at 78 K. At larger coverages with potassium atoms an opposite effect is observed. An attempt has been made to compare the experimental results with the theoretical models suggested recently.
Surface Science 247 (1991) 269 273 North-Holland
269
Water adsorption on the NaC1 surface S. F~31sch and M. Henzler lnstitut ]'fir Festk6rperphysik, Appelstrasse 2, W-3000 Hannover, Germany Received 21 May 1990; accepted for publication 7 September 1990 H 2 0 adsorption on epitaxial NaCI films has been investigated by UPS, XPS and EELS, focused on the dependence of the adsorption behaviour on the defect-structure of the substrate. On the smooth, homogeneous surface only molecular adsorption is observed. A three-dimensional ice-layer grows at a deposition temperature of 130 K. After desorption of the H 2 0 layer (145 K at 1 )< 10 -6 Pa partial H 2 0 pressure) a small a m o u n t of H 2 0 molecules remains on the surface in a modified state of bonding. Surface color centers produced by electron b o m b a r d m e n t however induce chemisorption. These defects act as reactive sites which cause dissociation and OH production.
274
Atom ion transition energies for alkali atoms
Surface Science 247 (1991) 274-278 North-Holland
on
a tungsten surface
Longin Gladyszewski and Grzegorz Gladyszewski Institute of Physics, Maria Curie-Sktodowska Unioersity, 20-031 Lublin, Poland Received 21 May 1990; accepted for publication 20 August 1990 lon Qi and atom Qa desorption energies for five alkali metals on tungsten were determined using the ion thermal emission noise method. We present the results of calculations of the activation energy E for the charge transfer process on the tungsten surface. A special energetic balance equation for determining E is used: (Qa - Qi) + e ( V - ~) + E = 0; (V is the ionization potential).
Surface Science 247 (1991) 279-283 North-Holland
279
Coadsorption of beryllium and potassium on a (112) tungsten plane Z. Dworecki Institute of Physics, Pedagogical Unioersity, Oleska 48, 45-052 Opole, Poland Received 21 May 1990; accepted for publication 19 September 1990 The adsorption and coadsorption of beryllium and potassium on the tungsten (112) plane was studied using a probe-hole field electron microscope (FEM). Measurements were made at 78 K for potassium and at 300 K for beryllium. It has been found that the adsorption of potassium decreases and that of beryllium increases the work-function of the (112) W plane. At small coverages with potassium atoms (O K < 0.2) on the (112) W plane succesive evaporation of beryllium atoms causes a decrease of the work-function at 78 K. At larger coverages with potassium atoms an opposite effect is observed. An attempt has been made to compare the experimental results with the theoretical models suggested recently.