******************************* Our Bhumihar Ratna - 9 ******************************************** Professor D.K. Rai (1943 -- 2012): ******************************************** A great Spectroscopist, Quantum Chemist & a Teacher: ********************************************************************** It was one of the saddest moments in my life when I received the telephone call conveying the news of death of Professor Devendra Kumar Rai on 12 July 2012 while I was visiting California. He was one of my best teachers, a noble colleague and trusted friend in BHU for the past four decades. In 1958, when I joined the Central Hindu College at Kamachha in Varanasi as a first year Intermediate Science student the teachers of Physics, Chemistry and Mathematics were intimately connected with their respective Departments in the main campus of Banaras Hindu University (BHU). The levels of teaching and laboratory work were very high and our teachers used to motivate and inspire the students by citing examples of their brilliant students of the past. Jayant Vishnu Narlikar was presented as one of the best most brilliant alumni who could solve complex problems which were very challenging even to the experts in the field. Professor Jayant Narlikar was by that time in the Cambridge University and many of us had already come to know about his achievements from newspapers. When I joined B.Sc. in 1960 and became a resident of Broacha Hostel of BHU we came to know about four very bright M.Sc. Physics students who used to visit the room of Govind Singh (who later became a professor of physics) for intense discussions followed by tea. In June 1961, when the results of M.Sc (Final) were announced Devendra Kumar Rai got the highest marks in spectroscopy, Ram Chandra Prasad Tata got highest marks in electronics, T.V.Ramakrishnan got highest marks in nuclear physics and Omkar Nath Srivastava got highest marks in solid state physics. The M.Sc. Physics batch of 1961 remains a unique example in which a large number of students brought glory to BHU by their personal achievements. Tata (T. R. Prasad) joined the IAS and served the country with distinction before his retirement from the post of Cabinet Secretary of the Government of India. Ramakrishnan went to USA for his higher studies and became very famous for his research contributions in condensed matter physics for which he got many awards and recognitions including FRS. Omkar Srivastava and Govind Singh, joined research under Professor A.R.Verma, carried out excellent experimental work in X-ray crystallography and Electron microscopy and later became renowned professors of physics in BHU. D.K. Rai had secured the highest marks among all the M.Sc. and M.A. students of 1961 and was awarded the Chancellor medal of BHU. He was appointed as a lecturer in the Department of Spectroscopy which had been created in 1953 out of the Physics Department in recognition of the research contributions of Professor R. K. Asundi in the field of experimental molecular spectroscopy. Looking back this was one of the best things that happened for the rapid research advancement of spectroscopy at BHU and credit must go to the then head of the department Professor Nand Lal Singh who envisioned Rai’s innovative capability and provided freedom to do research and earn his Ph.D. on a topic of his interest while fulfilling his teaching responsibilities. Devendra Kumar Rai was born in 1943 in village Reotipur of Ghazipur district in Uttar Pradesh and lost vision in one of his eyes due to a serious infection at a very tender age. To many of us, who had the privilege to observe him closely the physical disability never impeded his outstanding abilities as a teacher, brilliant researcher and a very kind and noble friend. His father was an employee of Allahabad Bank and when he was transferred from Calcutta (present Kolkata) to Banaras (present Varanasi) he brought his frail young son to Varanasi where medical and educational facilities were many times better than in his native village. Devendra completed his high school from Sanatan Dharm School, Varanasi and intermediate science from the Queen’s College, Varanasi before joining B.Sc. in 1957 at BHU. I remember meeting Dr. K.N. Upadhya in Spectroscopy Department in 1962, who was a student of my father in his high school at Sarnath, Varanasi, for advice of my postgraduate education. Dr Upadhya told me that experimental facilities had been enhanced in the Physics Department after the arrival of Professor A. R. Verma and the quality of teaching had been many fold enhanced by the appointment of D. K. Rai in the Spectroscopy Department. There was joint teaching for the students of physics and spectroscopy, in those days, except for the special papers and laboratory in the final year. I decided to join the Spectroscopy Department and after completing M.Sc. in 1964, got registered for my Ph.D. in experimental spectroscopy with Dr.K.N.Upadhya as my research supervisor. D K Rai and Dr. Upadhya used to share the same office which had one entrance from the laboratory and the other from the outside. Dr Upadhya had great affection for Rai and he had given the key of the outer door to the latter, who came to the department around 8 AM and leave after 6 PM even on Sundays. Rai was not only a brilliant scholar but also had deep regard and respect for his teachers and senior colleagues who in turn extended unreserved support in his academic pursuit. Dr. K.N. Upadhya stands singled out for his unselfish and very sincere support to Rai’s missions. I have never regretted my decision of opting spectroscopy as my specialization. I relished and enjoyed the excellent teaching of D. K. Rai in M.Sc. and his unique expertise in the interpretations and clear explanation of complex rotational fine structures in the spectra of diatomic and polyatomic molecules during the Ph.D. work which required knowledge of quantum mechanics. Rai’s efforts created an enabling R&D understanding in molecular spectroscopy research for the analysis of vibrational and rotatational structures of electronic bands by using state-of-the art theoretical tools to resolve, understand and explain deviations in the frequency and intensity of spectral bands under low resolution and of rotational lines at higher resolution. This could be possible because of his clear, precise and vast knowledge of quantum mechanics, group theory and statistics leading to a vastly improved quality of vibrational and rotational constants extracted from the experimental data. It was around 1962 that two researcher scholars, S.K.Tiwari and R.B.Singh, successfully installed and established operation of a new 35 feet concave grating spectrograph and that was a turning point which started a great spurt in photographing the high resolution emission as well as absorption spectra of diatomic and polyatomic molecules. There were more than a dozen research students working on various prisms and grating spectrographs in the laboratory. Since the time of Professor Asundi around 1950 an expertise had been developed in recording emission spectra of benzene and other large polyatomic molecules using specially designed electric discharge tubes which were to be continuously operated, in some cases, for more than 24 hours to record intense band spectra. Thus the laboratory remained open 24/7 and students working in the lab took turns to sleep on a large concrete table during the night. This concrete table served as the tea table in day time with Professor Nand Lal Singh where all the teachers and researchers were meeting for an hour at 1 PM to discuss the progress of various experiments. In addition to these discussions, a seminar was held every Saturday afternoon in which the research scholars as well as the postgraduate students were encouraged to speak on various aspects of atomic and molecular spectroscopy. D.K. Rai, who participated in all the academic activities, was always available in his office after his teaching duties and was seen discussing problems with research scholars or reading scientific journals. Prof. Rai was conducting Ph.D. work on the potential functions of molecules while teaching and working with research scholars in their analyses of molecular spectra He developed algorithmic and wrote a computer program for calculating potential energy curves of diatomic molecules using the vast experimental data that had been available on the vibrational and rotational constants of a large number of molecules studied at BHU. Professor A. N. Singh and Dr. R.B. Singh who were research scholars in those days rendered him much help in this emerging area of theoretical research. The nearest computer facility in those days was at IIT Kanpur and with the generous support of Professor Putcha Venkateshwarlu of IIT Kanpur, R. B. Singh was able to carry out calculations of potential energy curves. It was possible to determine the values of dissociation energies in the ground as well as excited electronic states of diatomic molecules in addition to explaining the pre-dissociations due to crossing of the potential energy curves of bound and repulsive electronic states of several diatomic molecules. Prof. Rai was awarded a SIDA fellowship to work in the Quantum Chemistry group of Professor Per O. Lowdin at Uppsala in Sweden and he worked very hard during the summer vacation of 1965 to submit his Ph.D. thesis before leaving for Sweden in July. The Ph.D. thesis of Professor Rai embodies the results of true potential curves in ground and several excited electronic states of more than two dozen diatomic molecules. Many of these molecules are of great importance in the earth’s atmosphere and the knowledge of their potential curves has proved helpful in understanding the complex chemical reactions that determine the quality of our atmosphere. Professor Rai’s research contribution has acted like the foundation stone for the subsequent quality and depth of experimental investigations on the rotational and vibrational spectroscopy of diatomic molecules at BHU. The doctoral theses subsequently submitted in spectroscopy contained not only the precise rotational and vibrational constants of diatomic molecules but also the use of these constants to determine true potential curves. This led to knowledge on the nature of molecular bonding in terms of molecular orbitals and also the dynamics of these molecules in their ground and excited electronic states. The availability of infrared spectrophotometers at BHU since 1960 complemented and supplemented the vibrational frequency data in the ground states of the polyatomic molecules obtained from their emission and absorption spectroscopy. Dr. Rai used these experimental data in the construction of potential functions of polyatomic molecules in the light of the pioneering work of Professor E. B. Wilson by using various approximations for the molecular force field. The General Valence Force Field (GVFF) involved too many force constants which could not be determined from the vibrational frequencies of normal modes of a single molecule and the information on its various isotopic species was not easily available. The initial work, therefore, started with the Urey-Bradley Force Field (UBFF) which involved a smaller number of force constants. He also modified this approximation to include some of the important interaction force constants to get a more realistic potential function of the polyatomic molecule in its ground electronic state. In those cases where isotopic data were available GVFF was used to determine the intra-molecular force constants. The force constants of a related group of molecules also shed light on the nature of the molecular orbitals involved in their various chemical bonds. In addition to a large number of research publications, this work provided an impetus for younger research scholars to advance their experimental work on electronic and vibrational spectroscopy of molecules with the normal coordinate analyses. During his one year stay in Uppsala Dr. Rai perfected the techniques of molecular orbital approach to calculate molecular properties in ground as well as excited electronic states. He worked on the problem of hydrogen bonding in DNA double helix which was genesis of his interest in molecules of biological importance. He came in contact of Professor Khetrapal who was also in Uppsala during that period. After his return to BHU in July 1966 he started quantum chemical calculations on derivatives of benzene, naphthalene and other organic molecules whose electronic spectra had been studied since the time of Professor Asundi for whom Spectroscopy Department was established as a separate unit from the parent Physics Department in early 1950s.The novel advancements in the science of spectroscopy initiated by Dr. Rai led the foundations of understanding of biological properties of molecules in terms of their molecular orbitals which gave rise to a new era of research in Biophysics that has led to its addition as a specialization in the physics department since 2009. I remember Professor G.N. Ramachandran visiting the Physics Department around 1970 to give lectures on the famous Ramachandran plot. He was a wonderful speaker but he was very serious looking and we were surprised when he came into the spectroscopy laboratory next morning to meet Dr. D. K. Rai in his office. It seems that he had come across the quantum theoretical work on large molecules carried out at BHU and there was an intense discussion between the two for more than an hour. A couple of years later Dr Rai joined the Molecular Biophysics Unit of Professor Ramachandran at the Indian Institute of Science in Bangalore as a visiting faculty for a few months. In early 1970s Spectroscopy was merged into the parent Physics department and Dr Rai was appointed as the Professor of Spectroscopy, a post which had been originally created for Professor Asundi. Atoms as well as molecules are probed with electron impact to reveal their structure and dynamics. An atom or molecule may reach a higher electronic state of the neutral or ionized species due to its impact with electrons. The dynamics of the excited state may lead to a radiative transition and the resulting spectrum gives information about the atomic or molecular constants. The molecule in the excited state may also subsequently decay nonradiatively or the atom may exhibit Auger effect. The behavior of atoms and molecules in collision with electrons are of immense importance in understanding the origin of laser emission from them. Professor Rai also made very significant contributions in theoretical understanding of electron-atom and electron-molecule collisions leading to award of Ph.D. degree to several students. The electron emitted by the atom or molecule comes out with a momentum in a specific direction. The angular distribution of the emitted electron gives information on the type of atomic or molecular orbital from which it is ejected by the impinging electron. In early 1980’s Dr. R. Shanker, a former student of spectroscopy, joined the physics department and started experimental work on electron-atom and electron-molecule collision. With very hard and dedicated endeavor Professor Shanker has established the Atomic Physics laboratory leading to very interesting results in recent years on the ionization of atoms and molecules and the fragmentation of the latter due to electron impact. Although a Ruby laser had been brought by Professor J. G. Winans of Buffalo University who came to Spectroscopy laboratory for a year in 1968 as a visiting Fulbright Professor the experimental work on lasers and laser spectroscopy got accelerated because of the major initiatives of Professor D. K. Rai in mid 1970s. In addition to the techniques of laser fluorescence and laser Raman spectroscopy novel techniques of laser two-photon spectroscopy, laser photo-acoustic spectroscopy and laser opto-galvanic spectroscopy were developed, nurtured and perfected to enhance the quality of research at BHU. Photoacoustic spectroscopy was used not only to explore matter in the vapour phase but also to record the spectral features of condensed matter samples including biological samples that did not fluoresce when irradiated by a tunable laser. Exotic stable and unstable neutral and ionic atomic and molecular species under electrical discharge were studied for the spectral and dynamical properties in their highly excited electronic states. Bright young students were attracted to work in these new fields of theoretical and experimental research and they not only enriched the spectroscopy laboratory of BHU but also made important and significant contributions at the national as well as international level. Professor Rajesh Srivastava at IIT Roorkee, Professor J.P.Singh at Mississippi State University, USA, Professor A. K. Rai at Allahabad University, Dr Narayanan Kuthirummal at College of Charleston, USA, Dr K K Mahato at Manipal University and several others like them belong to this generation who have enhanced the prestige of BHU by their contributions to spectroscopy. After the establishment of Center of Advanced Studies in Physics at BHU there was a shift toward spectroscopic studies of solid and nano materials. The experimental studies on doped glassy materials were vigorously carried out after 2000 and Professor Rai continued to make valuable contributions in explanations of phenomena of frequency up-conversion and quantum cutting in glasses doped with rare earth compounds. Though Professor S.B. Rai took the academic leadership of spectroscopy research after the retirement of Professor D.K.Rai in 2005 but the latter continued his association as emeritus professor and kept his routine and punctuality of arriving at the spectroscopy laboratory early in the morning till 11 July 2012, a day before his abode to the heavens. Professor D.K. Rai was a true follower, admirer and devotee of Pt Madan Mohan Malviya, the founder of the Banaras Hindu University and considered himself very privileged and fortunate to serve one of the great Academic Institutions on the earth which had been started in1916 by donations right from the poorest of poor Indians to the Maharajas of pre-independent India. Following footsteps of Malviyaji, Prof. Rai was a great proponent of imparting science education in Hindi and in addition to innumerable scientific articles, he wrote books in Hindi on Sir C V Raman and Laser Applications. He made valuable contributions to scientific terminology in collaboration with Dr. S.K. Tiwari in Hindi and was a regular author of scientific articles for Vigyan Parishad Allahabad which celebrated centenary of its existence shortly before his death. He was editor of BHU Journal of Scientific Research for many years and made several changes to enhance the quality of articles published in it. He was also the chief editor of the University magazine “PRAJNA” for many years and was instrumental in publications of its memorable issues on the life and work of Nicolaus Copernicus and Sir Chandrasekhara Venkata Raman. He was the founder of Laser and Spectroscopy Society of India (LASSI) and president of the physics section of Indian Science Congress at its annual session in Madurai. Prof. Rai was on the editorial boards of the Indian Journal of Physics (Kolkata) and the Journal of Scientific Research of CSIR. He was member of DST for two terms and served on many committees of the University Grants Commission. He held the administrative positions of Head of Physics Department and Dean, Faculty of Science at BHU and served the community of students and the employees with great distinction. He was the senior-most professor of BHU for almost a decade and served as a member of its Executive Council, Academic Council and the Court. Above all, he was a great teacher and his interactions with undergraduate, postgraduate and research students both inside and outside the lecture halls and laboratory left them highly satisfied in the process of acquiring knowledge and clear understanding of complex nature of electrons and molecules. He shunned publicity and was a rare example of humility and scholarship. He was a symbol of courage and hope in the most adverse conditions situations and crisis and he has left behind a large group of very promising and dedicated students, scholars, and researchers who will carry on his legacy into the future. S. N. Thakur Ex-Professor of Physics Banaras Hindu University Suggested By: Mr. Pradeep Singh
Posted on: Sun, 14 Sep 2014 09:11:05 +0000
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