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Maurice Barnett “Barney” Webb (May 14, 1926 – January 15, 2021) was an American Physicist who worked in the field of Surface Science, finishing his career as professor emeritus of physics at the University of Wisconsin-Madison. He was most noted for his work in establishing low energy electron diffraction (LEED) as a quantitative technique for the determination of atom arrangements at the surface of crystalline solids. He was also noted for devising clever experiments based on home built equipment to test fundamental concepts in surface science.

Early Life Webb was born in 1926 to a well to do family in Neenah, Wisconsin. His father James Webb was the owner of the local hardware store which had been founded by his mother Laura Barnett’s family generations earlier; her family also owned the local drug store. A month before his birth his sister Frances, then 6 years old, was kidnapped for ransom, but released unharmed later that same day at a nearby Fond du Lac, WI farm. Fred Hunde was eventually convicted of the crime and sentenced to life imprisonment, later commuted to 15 years. Five years later, in April 1931, the family was again threatened in an unsuccessful attempt to collect $3000 which the perpetrator, Roland David Hassinger, demanded the money be put into a package and thrown from a Soo Line train. The incidents had a dramatic effect on Webb’s mother, and he later recounted that he, his brother and sister lived sheltered childhoods as a result.

Education In spite of the above mentioned events he excelled in school, particularly in science - the 1944 Neenah Rocket, his high school yearbook, listed him as a member of the biology club and the forensics club, as well as the debate club, oratory club, a sergeant in the high school cadet corps, and yearbook editor; He was valedictorian of his graduating class. Following graduation Webb served briefly in the US Navy enrolling in the electronic technician program – his work involved diagnosing problems with ship radar and navigation system. In a typically self-deprecating account he later said that mainly he looked to see seemingly faulty instruments were plugged in properly. After the end of World War II he enrolled as an undergraduate at the University of Wisconsin-Madison, initially as a premedical student, but based upon interesting courses in physics, including one taught by Ragnar Oswald Rollefson, he switched to a physics major in his second year at the UW-Madison. While an undergraduate he spent summers at the Institute of Paper Chemistry in Appleton, WI, studying the effects of coatings on the optical properties of paper. In 1956 he began a PhD program, again at the UW-Madison. In those days two of the principal areas of investigation in the department were Nuclear Physics, in which Heinz Barshall and Raymond Herb were notable research leaders,  and Low temperature physics - the UW was one of very few universities with a He liquefaction system. He opted for the latter, initially working in the research group of Professor Frank Rogers. Rogers and Rollefson however soon joined the MIT Lincoln Laboratories, which were developing technologies connected to the DoD Defense Early Warning (DEW) line project, and brought their graduate students with them; Webb chose to return to the UW after only a year. He then joined the group of William “Bill” Beeman who was carrying out SAXS investigations of structures resulting from cold working of metals. In his PhD thesis he studied the polarization dependence of the scattered x-rays, and identifying features in the SAXS measurements as due to double scattering from grain boundaries rather than density fluctuations. Professional Life From graduate school he immediately joined the General Electric Research Labs, then one of the premier industrial R&D institutions, where he studied various aspects of metal thin films, including whisker formation, transport properties, and cyclotron resonances. In 1961 the UW-Madison enticed him to return as a tenured Associate Professor. There he established himself as both a leading researcher and as a truly gifted mentor. Nearly all of his graduate students became professors of physics or engineering, or researchers in industry and at national laboratories. His contributions were mainly in Surface Science, a field in which he was one of the architects, and for which he was recognized with the 1987 APS Davisson-Germer award. This was an especially fitting honor: while at GE he had heard a lecture by Lester Germer on electron diffraction, and this motivated him to adopt low energy electron diffraction (LEED) as the focus for his research. As was generally recognized at the time a challenge in using the diffracted intensities to determine atom arrangements is the much stronger coupling of the incident radiation, i.e. electrons, to atoms than would be the case for x-ray diffraction (XRD); this means surface sensitivity, but also that multiple scattering is even more important in LEED than in XRD. As he noted in a seminal review monograph by Webb and his former student Max Lagally, published in the journal Solid State Physics, the multiple scattering contribution is dependent not only on the momentum transfer, but also in the incident direction of the electrons; he proposed an approach involving averaging the intensity within a diffracted beam over a broad range of incident angles to allow for a simpler, quasi kinematic interpretation of the intensity in terms of the atom arrangement. A second important difference between LEED and XRD is the effect of temperature on the diffraction-in a series of papers he and his students explained the difference in the form of the single-photon scattering, which falls off like the inverse of the phonon momentum in LEED as compared to the inverse square dependence in XRD as resulting from the finite penetration of the incident radiation in the latter case, and demonstrated this by direct integration of the intensity over the appropriate 2D Brillouin zone. He was not however limited to a single experimental technique. Instead Barney approached scientific problems with a very powerful tool: his deep physical insight. Indeed, his true gift was an ability to see through a complex problem and expose the underlying physical principles. This insight allowed him to design often deceptively simple experiments to uncover the driving physics in these nearly 2-d systems. A significant example is provided by a series of experiments he and his students carried out at cryogenic temperatures where noble gas atoms like xenon or krypton adsorb to solid surfaces. Their earliest work used single crystal silver as a substrate which mainly provided a confining potential, keeping the atoms close to the surface, but allowing the interactions of these atoms to be probed via the attenuation of a signal from the underlying surface, such as the Auger electron intensity. This work allowed the interactions of atoms in a nearly two dimensional system to be probed, and contributing to the understanding of ordering in reduced dimensionality. In an insightful extension of this approach, he and his students examined the effect of adsorption of noble gas atoms on reconstructed semiconductor surfaces, measuring the pressure vs temperature dependence of stepwise attenuation of the substrate Auger signal, and comparing this with calculated “isosteres” based upon pairwise Lennard-Jones interactions between the noble gas adatoms and the underlying substrate atoms – Webb reasoned that these are weak compared to those determining the reconstruction, and that a discrimination between model geometries was possible. As another example, in the mid 1980’s the several surface reconstructions suggested a competition between bond-breaking energies and strain energy. Barney devised a simple approach to apply stress directly to a solid wafer and observe the results of strain on surface structure via electron diffraction. For decades he was a fixture at the APS March meeting, the AVS meetings and the UW Physics colloquia-which he never missed, always sitting in the front row and always with basic insights for the speaker and audience, regardless of the topic. He had a charming, self-effacing approach, often beginning a scientific discussion by saying “I don’t know much about that, but…” at which point it would become clear that he in fact had grasped the issue to its essence. He stayed active throughout his career, using summer visits to Bell Labs to stay abreast of developments in technology, and shepherding his graduate students through talks at numerous conferences. His students often related stories of the hours he would spend training them to give talks at meetings, along with his fatherly approach to mentoring, his love of science, and his devotion to the UW and the physics community in general. Throughout his career Webb was an unapologetic proponent of curiosity driven science-he would often reply to our updates on current research with detailed questions, but ending with: “so, you’re having fun.” Personal Life Beyond science Barney displayed an impressively wide range of talents and interests. He was a skilled woodworker, building furniture, and innovating fixtures for making precise joints. He loved to cook, bringing into play his scientific bent here as well-he once described the right way to poach an egg, adding a drop of vinegar to the water to congeal the albumen. He was competitive in a number of sports, including ping-pong (one of his former students recounts thinking himself proficient until playing against Barney-“he toyed with me”), and above all sailing. Early Webb graduate students recount occasional group meetings on board his boat “The Half Hitch”. He brought an intelligent, reasoned approach to conversations on myriad topics including politics, and the effect that bigtime sports was having on higher education. Of the value of the latter he was fully convinced, once remarking that the GI Bill at the end of World War II, which allowed soldiers to attend the University was one of the best investments ever made, and drove the subsequent success of the US in the 20th century.

Later Years In 1996 on the occasion of his 70th birthday, many of his students united at the “Webbfest” at the University of Wisconsin-Madison to share talks illustrating how he had helped to shape their careers. 15 years later, at 85, and after a decade of “official” retirement, he gave his own reflections at a second get together of students and colleagues, in which he remarked that the most gratifying aspect of his career had been interaction with his students-he clearly meant this. His commitment to the UW-Madison Physics department did not end with this swansong: he continued over the final decade of his life to come into work for scientific discussions on the latest directions in Physics, and for lunch with younger colleagues and former students, offering insights and sage advice to the end of his life, at 94 years. His legacy lives on through the insights that he passed on to the Physics community.