Obituary for Prof. Gianni Ascarelli (1931-1995)
Gianni Ascarelli passed away on September 24, 1995, after a four-year struggle with cancer.
Ascarelli was born in Rome, Italy on October 25, 1931. His father, Tullio, a highly respected scholar in the field of commercial law, was a professor at the University of Rome. As a result of the racial laws enacted by the fascist government led by Benito Mussolini, he was forced to resign his university position and left the country in 1938. The family resettled in São Paulo (Brazil) where Ascarelli received his early education. After the end of the 2nd World War, the Ascarelli family was able to return to Italy in 1948 and resume a normal life. Ascarelli, who had received a B.S. degree in physics at the University of S. Paulo, enrolled at the university of Rome, and obtained a physics degree ("Laurea") in 1954.
After receiving his degree, Ascarelli worked for a short period as Research Assistant in the Physics Department of the "Istituto Superiore di Sanità", the Italian equivalent of the National Institutes of Health, under the direction of Professor M. Ageno.
The possibilities for research and a career in the postwar years in Italy were quite limited, so Ascarelli decided to broaden his horizons, and in 1955 he sailed to the United States, and enrolled as a physics graduate student at M.I.T. After obtaining his Ph.D., he moved to the University of Illinois in 1959, and worked under the supervision of Professor F. Brown as a postdoctoral research associate.
In 1961 Ascarelli went back to Italy, to assume the position of a Group Leader with C.N.R. (the Italian National Research Council) and Lecturer at the University of Rome. Meanwhile technological development had gained high priority on the agenda of the U.S. Government, and great opportunities became available for careers in science. The Physics Department of Purdue was in a stage of expansion and Ascarelli felt a desire to develop his scientific career in the U.S. In 1964 he joined the Purdue faculty as Associate Professor, and was promoted Full Professor in 1970. He was Visiting Professor at the University of Grenoble, France, during the academic year 1972-73. He was a Fulbright Visiting Scientist at the Synchrotron Laboratory (DESY) in Hamburg (Germany) and at the Max-Planck Institute in Grenoble (France) during the academic year 1991-92. In 1993-94 he was a Senior Fellow of the European Economic Community at the High Magnetic Field Laboratory in Grenoble.
Ascarelli's research interests were initially focussed on solid state physics, with emphasis on the properties of semiconductors (germanium and silicon) and ionic crystals (silver halides). In the early 1960's he made several pioneering contributions to solid state spectroscopy through the innovative use of the modulation techniques he invented. He studied recombination, low field breakdown processes as well as nuclear magnetic resonance phenomena in doped semiconductors (mostly Ge and Si). It was in this period that he also began his cyclotron resonance studies. Cyclotron resonance was a tool to which Ascarelli often made recourse later on, as his interests moved to different physical systems. By employing optical absorption techniques Ascarelli proceeded then to establish at Purdue a strong effort aimed at exploring the physics of excitons and the electron-phonon coupling in semiconductors. This led to important measurements of the temperature dependence of the polaron self-energy. He also determined how the electron-phonon coupling is influenced by the impurities, and how in turn it influences the excited states of the color centers in alkali halides.
Alongside his work on semiconductors, Ascarelli also developed a keen interest in the optical properties of biologically relevant materials. His activity in this area involved using far infrared techniques to establish the vibrational spectrum of a number of biological systems. To this end, he began to utilize submillimeter cyclotron resonance with suitable lasers. He also explored the effects of the application of relatively high magnetic fields on biological systems. Having dealt extensively with aqueous solutions, Ascarelli became interested in the intriguing, fundamental problems associated with the mobility and the transport properties of electrons in liquids.
During the past fifteen years or so Ascarelli's main field of research has been the exploration of electron energy levels and electron transport in some nonpolar dielectric liquids, mainly those of the rare gases. He studied the formation of the liquid band structure as it evolves with increasing fluid density. He succeeded, among other things, in measuring (for the first time) the Hall mobility in several such fluids as a function of density and temperature, including the vicinity of the critical point, and formulated a new model for the electron mobility in rare gas liquids which incorporates the effects of large density fluctuations near the critical point. He also succeeded in measuring indirectly the exciton effective mass in liquid xenon, in cooperation with a group from Jerusalem and Hamburg. While measuring the electron mobility, he also found an apparent discontinuity in the density of liquid argon along isobars slightly above the critical temperature, and the possibility of a surface phase transition drew his attention. Later on he was able to resolve this mystery by estimating the effects of capillary condensation. His last concern was the direct measurement of the effective electron mass in liquid rare gases, using cyclotron resonance, and even on his deathbed he made sure that his idea and project should be pursued, namely by a group from Québec, Canada.
Ascarelli's research was characterized by an attempt to identify an issue on which there might be a conceptual or an experimental difficulty, and then design an experiment to address the point in question. This was, the case in his measurements of the Hall mobility of electrons injected in insulating liquids. As a result of careful measurements, he was able to show the existence of weak localization in the heavy rare-gas liquids. Weak localization is the result of a quantum interference effect that had been previously found only at liquid helium temperatures.
Ascarelli also made important theoretical contributions such as his model of the electron mobility in rare-gas liquids. From a comparison of the model calculations and experiment, he was able to evaluate the density dependence of the effective mass of electrons in liquid argon and xenon.
Ascarelli was fluent in French, English, Italian, Portuguese and was able to give physics lectures and seminars in all these languages.
He was an outstanding experimentalist. Always full of ideas and plans, he was meticulous in the execution of his projects, being involved in every detail. He set very high standards for himself and his coworkers. He preferred to do everything alone in some cases in order to meet these standards. His very fruitful and imaginative experimental work was based on deep and thorough understanding of the relevant theories. He was always open to new ideas and developments, and contributed by advice and discussions to the research of many people who consulted with him. He cooperated closely and successfully with several groups in various countries.
He continued his experimental work during his severe terminal illness, even when his condition made this very difficult. Gianni Ascarelli was a rigorous person, demanding much from his students and colleagues alike. This trait, alongside his urge to firmly uphold his moral principles and opinions, caused at times disagreements and misunderstandings. In some occasions this led to taking issue with higher authorities, a task from which he proudly never shied, nor lacked zeal and creativity for. He was a loyal, pleasant and always helpful colleague and friend. He will be missed by many.
Gabriele F. Giuliani
West Lafayette, Indiana
Université de Sherbrooke
Sherbrooke, Québec, Canada
|Itzhak T. Steinberger
The Hebrew University
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