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Adsorption isotherms and heat capacity of 4He adsorbed on MgO smoke
A598 Surface Science 162 (1985) 453-460 North-Holland, Amsterdam
453
CORE-LEVEL BINDING ENERGIES AND AUGER ELECTRON ENERGIES IN EPITAXIAL RARE-GAS LAYERS ON GRAPHITE T. M A N D E L ,
M. D O M K E ,
G. K A I N D L ,
C. L A U B S C H A T
(001)
and
M. P R I E T S C H lnstitut f(tr Atom- und FestkOrperphysik, Freie Universiti~t Berlin, Arnimallee 14, D- 1000 Berlin 33, German)'
and U. M I D D E L M A N N
a n d K. H O R N
Fritz - Haber Institut der Max- Planck Gesellschaft, Faradayweg 4 - 6, D - 1000 Berlin 33, Germany Received 1 April 1985; accepted for publication 10 May 1985
Layer-dependent shifts of core-level binding energies and Auger electron kinetic energies are reported for epitaxial muhilayers for Xe, Kr, and Ar adsorbed on graphite (001). Despite negligible changes of the substrate work function, clearly resolved shifts are observed, which are described by layer-dependent hole screening effects. As with metallic substrates, the Auger electron energies shift three times more than the core-level binding energies, but the magnitudes of the shifts are reduced due to the small electron density in graphite.
Surface Science 162 (1985) 461-469 North-Holland, Amsterdam ADSORPTION ADSORBED
ISOTHERMS
461 AND HEAT CAPACITY OF 4He
ON MgO SMOKE
T i m o t h y S. S U L L I V A N ,
*
A l d o D. M I G O N E
a n d O s c a r E. V I L C H E S
Department of Physcis, University of Veasnington, Seattle, Washington 98195, USA
Received 1 April 1985; accepted for publication 6 May 1985 Adsorption isotherms at temperatures of 4.23, 3.97, and 3.76 K, and heat capacity measurements for three coverages in the range between 1.0 < T < 4.2 K are reported for 4He adsorbed on MgO. The isotherms were measured on a substrate consisting of pure MgO smoke in a quartz container. The heat capacity measurements were made on a sample consisting of MgO smoke deposited on quartz fibers, the fibers then enclosed in a quartz calorimeter cell. The isotherms show no special features, being taken considerably above the temperature of any expected fluid-vapor coexistence. The heat capacity measurements show solid-like behavior for the two highest coverages, while the lower coverage run (at approximately 0.029 ,~,-2) shows two-dimensional gas-like behavior. The heat of adsorption determined from the isotherms is qst ~ 62 K, considerably smaller than for 4He/graphite. Desorption effects are apparent in the heat capacity measurements above about 3 K.
453
CORE-LEVEL BINDING ENERGIES AND AUGER ELECTRON ENERGIES IN EPITAXIAL RARE-GAS LAYERS ON GRAPHITE T. M A N D E L ,
M. D O M K E ,
G. K A I N D L ,
C. L A U B S C H A T
(001)
and
M. P R I E T S C H lnstitut f(tr Atom- und FestkOrperphysik, Freie Universiti~t Berlin, Arnimallee 14, D- 1000 Berlin 33, German)'
and U. M I D D E L M A N N
a n d K. H O R N
Fritz - Haber Institut der Max- Planck Gesellschaft, Faradayweg 4 - 6, D - 1000 Berlin 33, Germany Received 1 April 1985; accepted for publication 10 May 1985
Layer-dependent shifts of core-level binding energies and Auger electron kinetic energies are reported for epitaxial muhilayers for Xe, Kr, and Ar adsorbed on graphite (001). Despite negligible changes of the substrate work function, clearly resolved shifts are observed, which are described by layer-dependent hole screening effects. As with metallic substrates, the Auger electron energies shift three times more than the core-level binding energies, but the magnitudes of the shifts are reduced due to the small electron density in graphite.
Surface Science 162 (1985) 461-469 North-Holland, Amsterdam ADSORPTION ADSORBED
ISOTHERMS
461 AND HEAT CAPACITY OF 4He
ON MgO SMOKE
T i m o t h y S. S U L L I V A N ,
*
A l d o D. M I G O N E
a n d O s c a r E. V I L C H E S
Department of Physcis, University of Veasnington, Seattle, Washington 98195, USA
Received 1 April 1985; accepted for publication 6 May 1985 Adsorption isotherms at temperatures of 4.23, 3.97, and 3.76 K, and heat capacity measurements for three coverages in the range between 1.0 < T < 4.2 K are reported for 4He adsorbed on MgO. The isotherms were measured on a substrate consisting of pure MgO smoke in a quartz container. The heat capacity measurements were made on a sample consisting of MgO smoke deposited on quartz fibers, the fibers then enclosed in a quartz calorimeter cell. The isotherms show no special features, being taken considerably above the temperature of any expected fluid-vapor coexistence. The heat capacity measurements show solid-like behavior for the two highest coverages, while the lower coverage run (at approximately 0.029 ,~,-2) shows two-dimensional gas-like behavior. The heat of adsorption determined from the isotherms is qst ~ 62 K, considerably smaller than for 4He/graphite. Desorption effects are apparent in the heat capacity measurements above about 3 K.