He graduated from the Faculty of Science, University of Zagreb in 1962 in the field of experimental nuclear physics and was employed at the Ruđer Bošković Institute. At the same faculty, he obtained his Master’s degree in 1967, and his PhD in 1969, also in experimental nuclear physics.
His postdoctoral training took him to Canada, to the Department of Physics at the University of Ottawa. During his stay in Ottawa, from 1970 to 1972, he established a long-term collaboration that later resulted in his regular annual visits to Canada as a Visiting Professor. Within this collaboration, a joint research program was launched between the University of Ottawa and the Ruđer Bošković Institute, which he successfully coordinated.
Upon returning from Canada in 1973, based on his outstanding results, he was appointed Research Associate, and in 1975 he was elected Associate Professor at the University of Rijeka. In 1977 he became a Senior Research Associate and developed collaboration with Japan. He went as a Visiting Professor to Kyoto University, where he stayed for six months, until 1978. He was Visiting Professor at the University of Malaysia, Kuala Lumpur, in 1991, and at University Sains Malaysia, Penang, in 1993. In 2003, he was elected Full Professor at the Faculty of Medicine, University of Rijeka.
He was appointed Head of the Laboratory for Electromagnetic and Weak Interactions at the Institute in 1979 and held that position until his retirement in 2003.
Among the many functions Dr. Ljubičić carried out, the most important were: President of the Scientific Council of OOUR FEP, President of the Physics Research Council, Head of the Department of Physics at the Institute, and Head of the Division of Experimental Physics. He also led numerous national and international research projects. He played an organizational and scientific role as Director of the program “Research in Subatomic Physics”, funded by the Ministry of Science and Technology from 1996 to 2002. Since 2002, he has led the project “Massive Neutrinos and Astroparticles.”
The scientific interest of Dr. Ljubičić can be summarized in three areas. The first includes (i) higher-order processes in nuclear decays and atomic processes. Within this, he studied double inner bremsstrahlung, decay of nuclear states via the electron bridge, emission of electron–positron pairs in alpha decays, and the Pauli exclusion principle, for which he set the lowest limit on possible violations. This research resulted in an introductory note in the journal Nature.
(ii) Neutrino physics, which he began in 1986 as Croatian coordinator of the project on the use of thallium in solar neutrino detection (until 1991). He led the Zagreb group at CERN in neutrino oscillation research within the NOMAD experiment (from 1992 to 2001), and since 2000 he has also led the Zagreb group in the OPERA neutrino experiment.
(iii) More recently, he focused on astroparticle physics, studying dark matter in the Universe, i.e. the existence of axions, extra spatial dimensions, scalar particles, paraphotons, and dark energy in the Universe.
The results of this work are evident in more than 170 published papers in international journals, more than 2200 citations, supervision of 25 diploma theses, 9 master’s theses, and 7 doctoral theses, as well as contributions at national and international conferences and the organization of numerous scientific meetings.
Dr. Ljubičić was a member of the American Physical Society, a member of the Court of Honour (1993 to 1997) and of the Supervisory Board (from 1997) of the Croatian Physical Society. From 1985 to 1991, he was Vice-President, and from 1991 to 2006, Treasurer of the International Radiation Physics Society. In 1988, he stayed at the University of Yaounde in Cameroon and in 1990 at the Royal Scientific Society in Amman, Jordan, as an expert of the International Atomic Energy Agency in Vienna.
He received the Award of the Croatian Academy of Sciences and Arts in 1994 for contributions of special and lasting significance for Croatia in the field of natural sciences, and the State Award for Scientific Achievement in Nuclear and Atomic Physics in 1998.
Throughout his career, Dr. Ljubičić achieved outstanding, internationally recognized results, and in 2005, for his contribution to science, the development, and reputation of the Institute, he was awarded the honorary scientific title of “Distinguished Scientist of the Ruđer Bošković Institute.”
