This volume contains review articles which were written by the invited
speak- ers of the seventh International Summer Institute in Surface
Science (ISISS), held at the University of Wisconsin - Milwaukee in July
1985. The form of ISISS is a set of tutorial review lectures presented
over a one-week period by internationally recognized experts on various
aspects of surface science. Each speaker is asked, in addition, to write
a review article on his lecture topic. No single volume in the series
Chemistry and Physics of Solid Surfaces can possibly cover the entire
field of modern surface science. However, the series as a whole is
intended to provide experts and students alike with a comprehensive set
of reviews and literature references, particularly empha- sizing the
gas-solid interface. The collected articles from previous Summer
Institutes have been published under the following titles: Surface
Science: Recent Progress and Perspectives, Crit. Rev. Solid State Sci.
4, 125-559 (1974) Chemistry and Physics of Solid Surfaces, Vols. I, II,
and III (CRC Press, Boca Raton, FL 1976, 1979 and 1982), Vols. IV and V,
Springer Ser. Chern. Phys., Vols. 20 and 35, (Springer, Berlin,
Heidelberg 1982 and 1984). The field of catalysis, which has provided
the major impetus for the de- velopment of modern surface science, lost
two of its pioneers during 1984 and 1985: Professors G.-M. Schwab
(1899-1984) and p.k. Emmett (1900-1985).