the system is very close to thermal equilibrium 

 and that local thermodynamic variables can be 

 defined and measured. However, in many impor- 

 tant situations, the system is far from equilibrium 

 and the standard techniques and concepts do not 

 apply. Theory at present has little to say about 

 how to conceptualize this situation and conse- 

 quently the meaningful measurements or physical 

 parameters that characterize the system are not 

 known. Theoreticians and experimentalists will 

 address this difficult and fundamental question in 

 the future by studying metastable systems, sys- 

 tems containing very large gradients of properties, 

 and systems undergoing rapid dynamic changes. 



Surfaces 



NBS has made a major investment in surface 

 science, with theoretical and experimental work in 

 surface physics, surface chemistry, and metallurg- 

 ical corrosion. From all indications, this field is on 

 the threshold of many illuminating insights into 

 important areas of application such as catalysis, 

 corrosion, small particles, wear, and electronic 

 devices. 



An example of recent progress at NBS is the 

 discovery that ions liberated from absorbed mon- 

 olayers by electron-stimulated desorption have 

 sharply peaked angular distributions which have 

 the same symmetry as the single crystal sub- 

 strates. The directions of ion desorption are relat- 

 ed to the directions of bonds at surfaces, and the 

 measurements provide a significant new potential 

 for determining surface structure. 



Theoretical work has addressed the electronic 

 structure of chemisorbed atoms and in particular 

 the energy dependence of field emission and pho- 

 toemission of electrons from surfaces with ad- 

 sorbed layers. Recent work has predicted direc- 

 tional effects in photoemission from which chemi- 

 sorption orbitals and bonding geometries can be 

 inferred. Specifically, the angular dependence of 

 photoemitted electrons from "adatoms" bonded 

 to a substrate has been calculated on the basis of 

 further detailed calculations of the electron charge 

 densities in the adatom. As a whole, the work by 

 NBS workers and others on directional effects in 

 surface measurement techniques has added a new 

 dimension to the ability to observe, understand, 

 and control basic surface phenomena on an atom- 

 ic level. 



NBS is also known widely for its corrosion re- 

 search. For example, NBS corrosion research has 

 been responsible for much of the development of 

 ellipsometry into a quantitative tool for studying 

 surface corrosion buildup. Significant contribu- 

 tions were also made to the application of field 

 emission microscopy to gas-metal surface interac- 

 tions, surface structure, and surface diffusion. 



50 COMMERCE 



Surface science together with its applied fields 

 of catalysis and corrosion is rapidly becoming one 

 of the most significant scientific endeavors, not 

 only because of important applications, but be- 

 cause of the promise of marked advance in sci- 

 ence and technology as a result of the powerful 

 research tools and scientific momentum being 

 developed. NBS plans to play a significant role in 

 the Nation's surface studies in the future through 

 research in the relevant physics, chemistry, corro- 

 sion, and catalysis. In particular, NBS is chal- 

 lenged by technology's need to characterize the 

 geometric and electronic properties of catalytic 

 sites and by the need to measure the effects of 

 catalytic poisons at the atomic level. 



Experimentalists, in collaboration with the theo- 

 reticians, will continue to refine and advance the 

 growing array of improved analytical techniques 

 and contribute new insights and measures of elec- 

 tron-solid and gas-solid interactions and better 

 descriptions of the electronic structure of sur- 

 faces. 



Materials Science 



Progress in materials science remains dependent 

 on interdisciplinary scientific investigation and is a 

 crucial nexus of application for many areas of na- 

 tional concern such as energy, health, safety, 

 etc. NBS does substantial research in polymers, 

 metallurgy, ceramics, glass, and semiconductors, 

 and operates one of the Nation's most active re- 

 search nuclear reactors for the benefit of outside 

 users as well as for NBS. 



At NBS, key contributions have been made to 

 the characterization of polymers, and especially 

 to the description of polymer crystallization by 

 the chain folding process. Shortly after the idea of 

 chain folding was proposed, a series of papers 

 were issued at NBS that explained the important 

 experimental findings and that established a theo- 

 retical basis for the kinetics of chain folding in 

 terms of fluctuation theory. NBS pioneered in 

 establishing the properties of III/V semiconductor 

 oxides and was one of two groups that first found 

 superconductivity in semiconducting materials. 

 Mechanical properties and failure mechanisms in 

 all types of materials are long-term activities at 

 NBS. For example, NBS pioneered in measuring 

 the static fatigue of glass and has shown how 

 slow crack growth and acoustic emission can be 

 used to provide reliability control in brittle materi- 

 als. 



The fundamental principle in materials science 

 is to correlate the macroscopic properties of ma- 

 terials with the electronic, atomic, and microscop- 

 ic structure. Future challenges in materials thus 

 lie primarily in making this correlation more quan- 

 titative and inclusive. However, because this cor- 



