Preface: Phys. Status Solidi C 6/11

Abstract The 15th International Conference on Positron Annihilation (ICPA‐15) was held at Saha Institute of Nuclear Physics (SINP), 1/AF Bidhannagar, Kolkata, India, from 18–23 January 2009. There was also a pre‐conference International School on Positron Studies (ISPS), held from 14–16 January 2009 also on the campus of the Institute. The series of ICPA conferences are held every three years at different places in the world, providing a versatile forum for exchange of scientific ideas and discussion of results among the researchers in the field. This time, the ICPA conference series revisited India more than 20 years after the earlier one, ICPA‐7, had been held in New Delhi in 1985. In India, we have had a long tradition of positron research spanning over experiment and theory. To the best of our knowledge, experimentation in positron annihilation spectroscopy at SINP started some time back during the 1960s. However, another avenue, 'positronium chemistry' (electron–positron in a bound state designated as the lightest atom, serving as chemical probe), came into effect in the late 1980s and triggered activities of chemical phenomenology ranging from liquid systems to various molecular substrates. This paved the way for physicists and chemists to indulge in joint activities both in experimentation and in theory. These activities augmented over the years and resulted in the decision to host ICPA‐15 at SINP, Kolkata. The venue was chosen by the deciding committee of the ICPA series at McMaster University, Hamilton, Canada, and we gratefully acknowledge the same. Presently, we see a vast development of the subject, if one simply browses through the conference proceedings contents, even though several important contributions are still missing, since not all participants submitted papers. Also many others who had registered could not come for unforeseen tragic events that had affected the Indian subcontinent. But we are grateful to all the participants of the conference who have travelled far from different parts of the world, to arrive at Kolkata in January 2009 for ICPA‐15. Our special thanks go to the speaker of the keynote address, Prof. A. P. Mills and the five plenary speakers for enlightening the audience with their innovative and thoughtful lectures. We are also grateful to the thirty invited speakers for sharing their illuminating results with the participants. There were about thirty contributed oral papers under various subject heads, and about one hundred poster presentations throughout the evening sessions. Ten of the young scientists were awarded with certificates par excellence for their important work and choicest presentations in the valedictory session. The judges of these poster presentations had to do a great deal of work and the session chairpersons were careful and considerate to hold the session within limited time with many enthusiastic discussions. It was indeed a very busy gathering, with discussions some times lasting till the late evening. The social programme was also very eventful in order to enhance free mixing of the scientists from various places. The conference excursion was a river cruise on the river Hooghly (actually the river Ganges that flows by the city of Kolkata), followed by dinner on the boat. The conference banquet was arranged in a beautiful place called 'Swabhumi' depicting a glimpse of culture and the handicrafts park of Bengal in its natural green ambience with delicious food courts. The participants were also entertained by musical evenings with famous artists of the city and classical Indian dancers. In fact, every evening was very colourful and vibrant, followed by dinner. We would like to thank each and every participant (there were in all about 180 registered participants from 27 countries) who contributed towards the success of the conference, the session chairpersons, the referees who have undergone the task of carefully examining the papers submitted for the proceedings, the students, volunteers and the staff members of SINP whose untiring efforts helped us to run the conference smoothly. We also acknowledge the cooperation received from all the members of our Nuclear and Atomic Physics division along with all the sectors of SINP, members of the canteen, the guest house, the auditorium of SINP and thank them for offering all the facilities. We also thank our event manager Mr. R. L. Das, for managing the to and from transport as well as the accommodation. Last but not least, mention must be made of the cultural committee of the conference headed by Dr. Indrani Ray, for organising the cultural events and for her solo opening dance to rejoice the occasion of the meeting with so many distinguished guests from different countries on the starting day of the conference. Lastly, we thank our erstwhile Director of SINP, Prof. Bikash Sinha, for spending some of his valuable time with us, the positron researchers, for supporting and being the Patron of this conference. We also acknowledge the important suggestions received from Prof. Toshio Hyodo, Chairperson of the ICPA International Academic Advisory Committee, and for his kind visit to SINP and his friendly discussion with Organising Committee members prior to the ICPA‐15 conference. Finally, we wish the organisers of ICPA‐16 all the very best for their future endeavours for a successful conference at the University of Bristol, UK. With my sincerest regards to you all, Bichitra Ganguly, Convenor, ICPA‐15, August 2009

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