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Fellows Directory

Ian Percival

Professor Ian Percival FRS


Elected: 1985


Ian Percival has conducted work in both quantum mechanics and classical mechanics. He has studied relationships between quantal and classical systems and his work on fundamental theoretical problems has had many practical applications. He has introduced the notion of correspondence identities, elucidated their connection with dynamical symmetries and used them in the first applications of Monte Carlo trajectory methods to atomic collisions and to microwave ionisation of atoms. With the aid of new correspondence principle techniques, he has obtained accurate electron-impact cross sections essential for the interpretation of radio recombination line observations. He introduced the notions of regular and irregular spectra, thus initiating the study of quantum chaos and is application to molecules. His important contributions to quantal collision theory include studies of bounds, of the polarisation of impact radiation and of non-iterative techniques for the solution of integro-differential equations. He has made outstanding contributions to the theory of nonlinear, non-integrable Hamiltonian systems. These include the development of Fourier methods to distinguish regular and chaotic motion.

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