Special Issue Preface pubs.acs.org/JPCA
Tribute to Piergiorgio Casavecchia and Antonio Laganà
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t is a great pleasure for us to pay tribute to Piergiorgio (Piero by his friends) Casavecchia and Antonio Laganà for their contribution to the experimental and theoretical investigation of reaction dynamics. The publication of this Festschrift also corresponds to Antonio’s formal retirement from the University of Perugia upon reaching his 70th birthday. This event was celebrated at a meeting called, “Virtual Environments and Detailed Simulations of Molecular Processes”, which was held in Bettona, near Perugia, on the fourth and fifth of November 2015. The proceedings are available in the open-access e-magazine VIRT&L-COMM and can be accessed at http://www.hpc.unipg. it/ojs/index.php/virtlcomm/issue/view/13. Piero and Antonio have been two pillars of the Reaction Dynamics Group of the University of Perugia for the last 40 years. They joined the group (founded by Prof. Gian Gualberto Volpi) at almost the same time at the end of 1974. Piero was a postgraduate student, and Antonio obtained a temporary fulltime research contract after a few years spent as a teacher in a high school. During those years other people also started their careers in Volpi’s group, namely, Bruno Brunetti, Fernando Pirani, and Gaia Grossi, while Enzo Aquilanti, Giorgio Liuti, and Franco Vecchiocattivi had already joined a few years before. Piero, who has always enjoyed laboratory work, started experimental research activity in the molecular beam field working with Enzo Aquilanti on inelastic ion−atom collisions. Antonio, who was already mastering early computer programming languages, focused on theoretical and computational work by developing codes for the dynamical treatment of gas-phase processes. After a few years and at about the same time, both of them decided to improve their skills by going abroad to two wellestablished research groups: Piero at Berkeley, working with one of us (Y. T. Lee, 1977−1980), and Antonio at Manchester, also working with one of us (J. N. L. Connor, 1977−1978). To spend a period abroad practicing new techniques was a must for young people in Volpi’s group, and Antonio and Piero brought back new expertise to Perugia. Piero started the building up of a crossed molecular beam machine following the classical design of Y. T. Lee and D. R. Herschbach; Antonio developed his classical trajectory and semiclassical codes to perform calculations of transition probabilities for atom−diatom reactive and nonreactive collisions. Since then, they have untiringly continued their work with absolute dedication and with a strong pace, as many of their co-workers had the chance to experience. Tireless travelers, Piero and Antonio have visited numerous research laboratories and attended many conferences all over the world. For both of them, the only distraction from work could come from their wives, Stephanie and Giovanna, who somehow accepted their fate to share their husbands with science. Piero has been one of the prominent figures in the field of crossed molecular beams scattering for nearly 30 years. In 1980, after he learned the subtleties of crossed beam elastic and
Photo Credit: Stephanie Seymour
Special Issue: Piergiorgio Casavecchia and Antonio Lagana Festschrift Published: July 14, 2016 © 2016 American Chemical Society
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The Journal of Physical Chemistry A
because these developments opened up new exciting avenues of research in reaction dynamics and permitted his group to bridge the gap between dynamics and kinetics studies of elementary gas-phase reactions. Besides invitations to speak at numerous leading international conferences, Piero’s research on reaction dynamics was recognized by the 2008 Polanyi Medal awarded to him at the 20th International Symposium on Gas Kinetics by the Gas Kinetics group of the Royal Society of Chemistry for his “outstanding contributions to the field of reaction kinetics/dynamics”. He was also honored to chair and organize Faraday Discussion 157 “Molecular Reaction Dynamics in Gases, Liquids and Interfaces”, which was successfully held in 2012 at La Cittadella in Assisi (his preferred site for organizing meetings). Over the past several years Piero’s main scientific contributions have been on the dynamics of polyatomic multichannel nonadiabatic reactions, such as those of ground-state oxygen atoms with unsaturated hydrocarbons, which represent his main current interest. By exploiting soft electron ionization it has been possible, after 50 years from the pioneering kinetics work of Cvetanović (and others) on these reactions, to identify unambiguously all the primary reaction products and determine their branching ratios as a function of collision energy, to explore in detail, thanks to synergistic collaborative theoretical work, both statistical and dynamical, on ab initio surfaces including nonadiabatic couplings, the role played by intersystem crossing in these important combustion reactions and to achieve a detailed understanding of the complex reaction mechanisms. A fruitful collaboration with one of us (J.M.B.) led to benchmark joint experimental/theoretical papers on the prototypical multichannel reaction O(3P)+ethene. More recently, also the mechanism of even more complex reactions, such as O(3P)+propene and propyne, has been disentangled by combining the CMB work with high-level ab initio and statistical (nonadiabatic) calculations, in collaboration with Carlo Cavallotti (Polytechnic of Milan). From 2000 to 2004 Piero was the European Coordinator of an EC Research Training Network on Reaction Dynamics; he has also been team leader in two EC networks on Astrophysical Chemistry. He has been a visiting Miller Professor at Berkeley (USA) and Erskine Professor at Christchurch (New Zealand) as well as visiting professor at Orsay (France), at Dalian Institute of Chemical Physics (Dalian, China), and at University of Science and Technology of China (Hefei, China). Piero has been a member of the Editorial Board of PCCP and of the International Advisory Board of The Journal of Physical Chemistry A and of Chemical Physics; currently he is member of the International Advisory Board of PCCP and Chemical Physics Letters. Since 2002 he has been the scientific secretary of the International Symposium on Molecular Beams. In 2015 he became the coordinator of the Ph.D. school in Chemical Sciences at Perugia University. Antonio has made many contributions to the theory of chemical reactions and related nonreactive processes, both dynamical calculations and the construction of potential energy surfaces. In the early part of his career, this was mainly for the collinear configuration of the atoms, before moving into full three dimensions, as computers became more powerful and advances in theory were made. Two classes of reactions are particularly associated with the Laganà name
reactive scattering experiments in Berkeley, Piero started his independent research career in Perugia. After his advanced “Y. T. Lee type” crossed molecular beams (CMB) apparatus (made of Al alloy) was completed, he started with highresolution experiments on the determination of intermolecular forces via differential cross-section measurements for rare gas− rare gas and rare gas−diatom systems. This initial work opened the door for him to the club of the leading scattering people, where he got to know and collaborate with several prominent figures in the field. In 1989 Piero modified the universal CMB apparatus toward reactive scattering studies and started a broad research program on the dynamics of elementary reactions. Initially, the focus was on reactions of O(1D) with molecules of atmospheric interest. This work started to establish his reputation in the field of reaction dynamics. At that time he also got to know the international community active in molecular beam scattering and reaction dynamics/kinetics, as Piero describes in detail in his Autobiography. In the early 1990s he developed continuous supersonic beams of OH radicals and Cl atoms, and in the mid-1990s the first continuous supersonic beams of nitrogen atoms permitted the group to undertake, for the first time, their reactive scattering, a long-standing challenge in the field that had been tackled since the 1970s in several laboratories without much success. Frontier reactive scattering work on prototype systems, such as the three-atom abstraction Cl+H2 and insertion N(2D)+H2 and C(1D)+H2 reactions and the four-atom reactions OH+H2 and OH+CO, prompted synergistic, collaborative work over several years with leading theoreticians (Don Thrular, Millard Alexander, Joachim Werner, David Clary, George Schatz, Javier Aoiz, Luis Bañares, Jean-Michel Launay, Pascal Honvault). Those cutting-edge studies prompted him to the forefront in the area and gained him invitations to speak regularly at the most important conferences in the field. During that period Piero also organized and chaired three very successful International Conferences: COMET XVI-1999 (with Antonio as cochair), 26th International Symposium on Free Radicals-2001, and 14th SASP-Symposium on Atomic & Surface Physics-2004. Piero has not only collaborated with leading theoreticians but also prompted stimulating and fruitful collaborations with leading experimentalists, such as Tim Minton (on gas−liquid reactive scattering), Michel Costes and Christian Naulin (on carbon atom reactive scattering), and Sébastien Le Picard and Ian Sims (on astrochemically relevant reactions by combining dynamics and kinetics). In 2003, in order to overcome the main complication and limitation in CMB experiments on polyatomic multichannel reactions, that is, the dissociative ionization of reactants/ products under “hard” (70 eV) electron impact, he successfully implemented for the first time on a universal CMB apparatus the “soft” electron−ionization detection by using low-energy tunable electrons. This turned out to be a new twist in reactive scattering studies, which permitted the group to perform a new class of experiments, in particular, to tackle the detailed dynamics of polyatomic multichannel (nonadiabatic) reactions. In 2007 he performed the first CMB study of a radical− radical reaction using continuous supersonic beams. Intense beams of sulfur atoms were also developed, and collaborative dynamical-kinetics-theoretical work lead to the characterization of also the reactions of S(1D) with saturated and unsaturated hydrocarbons. The new work with soft electron ionization and the study of radical+radical reactions gained him significant recognition
(1) Li + FH → LiF + H and related reactions involving the atoms Na, K, Be, Mg, Cl, Br, I, O, C, N and Mu, D, T to 4566
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research and education (the e-tests EChemTest and the distributed Learning Objects repository GLOREP, in particular). In addition to his research work, Antonio has been very active in serving the wider community of reaction dynamists and molecular collision theorists. In particular, he has been the director of two NATO workshops on reaction dynamics and has organized, with others, many schools and conferences on computational science and its applications. Well known to the reaction dynamics community are three books that he edited: Supercomputer Algorithms for Reactivity, Dynamics and Kinetics of Small Molecules (1989), Reaction and Molecular Dynamics (coeditor: A. Riganelli, 2000), and Theory of Chemical Reaction Dynamics (coeditor G. Lendvay, 2004). He is also an editor of the open-access e-magazine, VIRT&L-COMM and serves on the editorial boards of several other periodicals. Antonio has also played a leading role in several important European initiatives involving chemistry, in particular, COST (Collaboration in Science and Technology) by chairing its Technical Committee and running some of its computational chemistry Actions, ECTN (European Chemistry Thematic Network) by chairing its Virtual Education Standing Committee and being a member of its Administrative Council, and EUCHEMS (European Chemical Sciences) by chairing its Computational Chemistry Division and being a member of its Executive Board. He has also played a key role in European initiatives for students’ mobility and in particular in the establishment of the Erasmus Mundus Theoretical Chemistry and Computational Modeling Master and Doctorate. We have only touched on some of Antonio’s scientific activities, but we should also mention that he was Director of the Computer Centre (1995−2001) and Director of the Department of Chemistry (2002−2013) at the University of Perugia. A wideranging and productive career! Finally, on a personal note, we thank Antonio and Piero for years of friendship. We, and all their colleagues, always valued their enthusiasm and cheerfulness in doing science. Best wishes for all your future endeavors.
disentangle the intricate relationships between masses, interactions, and vector correlations of this class of reactions (2) N + N2 → N2 + N; this reaction, and associated inelastic processes, e.g., N2 + N2, are important for modeling the entry of spacecraft into the atmospheres of planets containing large amounts of nitrogen Antonio has used a wide variety of theories in his research on the dynamics of chemical reactions, for example: • Quasiclassical computations of reaction probabilities, cross sections, and rate coefficients • Semiclassical techniques, including the use of uniform approximations, e.g., Airy, Bessel, and swallowtail, as well as applying the initial value representation to reactive collisions • Accurate and approximate quantum theories, both timedependent and time-independent • Mixed classical-quantum theories, in which some important degrees of freedom are treated quantally, the remainder classically Antonio has also been active in the construction of potential energy surfaces and the determination of intermolecular interactions for nonreactive systems, for example: • The accurate ab initio calculation of global potential energy surfaces, including stationary points • Use of different coordinate systems, e.g., hyperspherical coordinates • Adiabatic and diabatic representations • Stereodynamics • Bond-order and rotating bond-order functional representations • Multiple potential energy surfaces Examination of Antonio’s publications on the above topics reveals that he has been an inveterate traveler (sometimes for extended periods) to other universities and institutions outside of Italy in order to meet, and interact with, leading scientists in the field. His travels have taken him to Orsay (France); Bristol, Cambridge, and Manchester (U.K.); Vancouver (Canada); Los Alamos, NM, Norman, OK, and Pasadena, CA (USA); Salamanca (Spain); Jerusalem (Israel); Bielefeld (Germany); and Heraklion (Crete, Greece). Often he has made repeated visits to these places. Antonio has also visited many computer research centers over the years in order to learn about and access state-of-the-art machines. As well as the usual physical chemistry and chemical physics journals, Antonio has also published in computer science and plasma periodicals. Eleven papers resulted from his work in Manchester as a postdoctoral research associate with one of us (J. N. L. Connor). Antonio has always been interested in exploiting the technological evolution of computers for applications to chemical problems, e.g., parallel, concurrent, grid, and cloud computing. These developments have led Antonio to the concept of “virtual communities”, in which chained modules perform, for example, ab initio electronic structure calculations, potential energy fitting, dynamics calculations, etc. There is a synergistic sharing of software and hardware paid for by credits, depending on the importance of the project to the scientific community. The development of virtual communities naturally leads to consideration of “knowledge management” through his contribution to the European Open Science activities for
N. Balucani J. M. Bowman J. N. L. Connor Y. T. Lee
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