Ted Janssen

Theo Willem Jan Marie Janssen (August 13, 1936 – September 29, 2017) was a Dutch physicist and Full Professor of Theoretical Physics in Radboud University Nijmegen. Together with Pim de Wolff and Aloysio Janner, he was one of the founding fathers of N-dimensional crystallography.

Ted Janssen was born on 13 August 1936 in Vught, near 's-Hertogenbosch. After studying theoretical physics in Utrecht University, graduating under Leon van Hove,

In 1965, he became first PhD student of Aloysio Janner at the Catholic University Nijmegen.

He finished his PhD thesis, Crystallographic Groups in Space and Time, in 1968, thereby providing the theoretical basis of what would become the superspace approach.

In 1972, he was appointed as an Associate Professor in Nijmegen.

In 1995, he became promoted to full Professor of Theoretical Physics.

Together with Aloysio Janner he was one of the founders of the higher dimensional superspace approach in crystal structure analysis for the description of quasiperiodic crystals and modulated structures. For this work he received in 1998 the Gregori Aminoff Prize of the Royal Swedish Academy of Science (with P.M. de Wolff and A.G.M. Janner) and in 2014 the The Ewald prize of the International Union of Crystallography (with Janner) (2014), the most prestigious prizes in crystallography.

During his career he also had many guest professorships, such as in Leuven, Dijon, Lausanne, Paris, Nagoya and Sendai(2006, 2013).

• Janssen T, Chapuis G, Boissieu (2018). Aperiodic structures: from modulated structures to quasicrystals. Oxford Science Publications. ISBN 978-0-19-882444-2.
• “Crystallography of quasi-crystals” (T. Janssen, Acta Cryst. A42, 261-271, 1986)
• “Aperiodic crystals: a contradictio in terminis?” (T. Janssen, Phys. Rep. 168, 55-113, 1988)
• Aperiodic crystals. From modulated phases to quasicrystals: structure and properties. 2nd edition.
• IUCr Monographs on Crystallography 28; Oxford Science Publications. Oxford: Oxford University Press (ISBN 978-0-19-882444-2/pbk). xviii, 532 p. (2018).

Ted Janssen died in Groesbeek, Netherlands, on September 29, 2017.