Biographical Sketch of H. De Waard
Reprinted from the January 2000 edition of the Mössbauer Spectroscopy Newsletter, published as part of Volume 23, Issue 1 of the Mössbauer Effect Reference and Data Journal

Hendrik de Waard of Groningen, The Netherlands, has spent 40 years of his professional life focusing his attention on the Mössbauer effect, making him one of the early Mössbauer researchers. He continues to this day to be an active member of the international Mössbauer community.

Professor de Waard was born in Groningen on April 20, 1922, where he was raised and educated. He attended the City Gymnasium from 1934-1940 and studied at the University of Groningen from 1940 through the World War, except for two years until 1949 majoring in Physics and Mathematics. His early research was in atomic physics, beginning in 1942 by studying the scattering of vast electrons in a mercury vapor. Following the war in 1945, his research focused on showing the existence of polarization of electrons by double scattering them in a mercury vapor beam.

In 1948, he switched to nuclear spectroscopy and received his Doctorate in 1954 based on his thesis entitled "Scintillation coincidence studies of the decay of 181Hf and 193Os and the isomerism of odd proton nuclei".  It was through this research that he also developed methods for the measurement of short nuclear lifetime. It was during this period that he also assisted the laboratory courses for physics majors and taught electronics. He continued working with nuclear spectroscopy at the Limbelden Institute in Stockholm and in the Fysikum in Uppsala, with the group of Professor Kai Sigbahm and Dr. T. R. Gerholm. An important result of his work in Sweden was the discovery of negative parity states in 175Lu and 175Lu that could not be explained in terms of the shell model, as it was known at that time, but fitted well into the new model S. G. Nilsson had developed for a strongly deformed nuclei. He also developed a method for stabilizing scintillation spectrometers by the feedback of the fluctuating outward signal that became widely applied all over the world.

He returned to the University of Groningen in 1955, and obtained a Lectorate in Experimental Physics there in 1956 and received a Full Professorate in the same discipline in 1958. His initial investigations at the University of Groningen were on the measurement of polarization of beta particles expected on the basis of non-conservation of parity in beta decay.

During a year as a Visiting Professor at the University of Illinois in 1962, he started his research in the recently started field of Mössbauer spectroscopy, inaugurating the investigations of the 27.8 keV level in 129I. It was through these early studies that data from a variety of iodine compounds were obtained and correlations were shown between the isomer shift and the quadrupole coupling constants.

In 1965 with Dr. S. A. Drentje, he started investigations of sources made by ion implantation of radioactive isotopes and metals. This work turned out to be very successful and is continued to the present time. Of important interest has been the ion implantation into semiconductors. One of the surprising results was that, despite the heavy damage imparted by the penetrating ions to the metal, often most of the implanted ions lay in regular substituted sites of the metal. Investigations of implanted sources were later carried out using perturbed angular correlation and nuclear orientation. Important results of these measurements was a better understanding of the role of vacancies, particularly at the annealing stages.

Another special effect that has been explored is the formation of molecules in metals that may occur after implantation of more than one different input. Real isolated chemical bonds may be formed as evidence by the Mössbauer spectra of atomic complexes formed. Professor de Waard further investigated surface magnetization of iron foils with optomagnetic Kerr effect, Mössbauer spectroscopy, and perturbed angular correlation. Here a hereto unobserved phenomenon was reported: the surface only became magnetized after the bulk magnetization that is in an external field reaches more than 75% of the saturation value.  The phenomenon can be explained from the stability of closure domains at the surface.

In more recent years, collaborating with Professor Richard Frankel, they measured the magnetization curves of several types of magnetotactic bacteria in the mid 1990's. These bacteria contain permanent magnetic ferritic or sulphidic cores built up of separate grains contained in the submicroscopic vesicles, depending on the type of bacteria that can be demagnetized in pulse fields and subsequently remagnetized in the opposite direction.

Professor Hendrik de Waard has received numerous honors and recognitions, including Award of Membership into the Royal Netherlands Academy of Science, Fellowship to the American Physical Society, Steinmetz Medal of The Netherlands Society of "Volksuniversiteiten", and Honorary Membership to the European Physical Society.

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