Aleksander Jablonski

  Professor Aleksander Jablonski, the founder of physical researches at the Nicholas Copernicus University at Torun, was born on February 26, 1898 in Voskresenovka, Ukraine and in 1916, entered the University of Kharkov to study physics. His study at Kharkov was interrupted by his military service first in Russian and later in the then newly organized Polish Army during the World War I. 

At the end of 1918, when an independent Poland was re-created after more than 120 years of occupation by neighboring powers, Jablonski left Kharkov and arrived in Warsaw, where he entered the University of Warsaw to continue his study of physics. 

An enthusiastic musician, Jablonski played the first violin at the Warsaw Opera from 1921 to 1926 parallely to his studies at the University under Stefan Pienkowski for his doctorate, which he received in 1930 with a paper "On the influence of the change of the wavelength of excitation light on the fluorescence spectra". Although Jablonski left Opera in 1926 and devoted himself entirely to scientific work, music remained his great passion. 

After receiving his doctorate, Jablonski spent two years (1930-1931) as a fellow of the Rockefeller Foundation in Germany working with Peter Pringsheim at the Friedrich Wilhelm Universitat at Berlin and with Otto Stern in Hamburg. In 1934 he acquired his habilitation from the University of Warsaw with the thesis "On the influence of intermolecular interactions on the absorption and emission of light".

Throughout the 1920's and 30's the Department of Experimental Physics at the Warsaw University was an active center for studies on luminescence, under S. Pienkowski. During most of this period Jablonski worked both theoretically and experimentally on fundamental problems of photoluminescence of solutions as well as on the pressure effects on atomic spectral lines in gases.

His early work at Warsaw included measurements of absorption spectra of solutions and the experimental proof that the intensity distribution in the fluorescence spectra in typical cases is independent of the wavelength of the exciting light. He introduced then the concept of the "luminescent centre", i.e. the system composed of the excited molecule and its closest neighborhood. Using the Franck-Condon principle generalized on the case of such centers, Jablonski has explained the main features of the fluorescence phenomena in liquid solutions. In 1935 he has suggested the famous diagram, commonly known under his name, which makes it possible to explain both the kinetics and the spectra of fluorescence, phosphorescence and delayed fluorescence. In this diagram, which now serves as the starting point of all modern textbooks on photochemistry, a very essential role is played by a metastable state later identified by G. N. Lewis and M. Kasha and independently by A. N. Terminen as the triplet state. This identification was finally shown to be correct in experiments by C. A. Hutchison, B. W. Mangun, J. H. Van der Waals, and M. S. de Groot in the late 1950's who used the electron paramagnetic resonance techniques.

The problem that intrigued Jablonski for many years was the polarization of photoluminescence of solutions. To explain the experimental facts he distinguished the transition moments in absorption and in emission and analyzed various factors responsible for the depolarization of luminescence. In 1934 Jablonski proposed a method of the orientation of molecules in anisotropic matrices which serves now as an important tool in studies of linear dichroism and polarization caused by oriented molecules.

In particular, this method is now widely applied in biophysical investigations.

In 1931 Jablonski started to work in his second main field of research, namely the pressure broadening of spectral lines. In that year he as the very first person has recognized the analogy between the pressure broadening phenomena and the production of molecular spectra. This analogy was the starting point of the quantum-mechanical pressure broadening theory developed by him in the late 1930's and early 1940's. The Jablonski theory is based on two assumptions:

  1. the Born-Oppenheimer approximation for the wavefunctions of the quasi-molecule formed by the radiating and perturbing atoms during a collision, and
  2. the Franck-Condon principle in its quantum-mechanical formulation.
Starting from these two assumptions Jablonski has derived from quantum mechanics the quasi-static expression for the intensity distribution in far wings of spectral lines derived earlier on classical ground by H. Holtsmark, H. G. Kuhn and H. Margenau.

In April 1938 Jablonski accepted a faculty appointment at the Stefan Batory University at Vilna, where he developed experimental studies of pressure broadening of atomic spectral lines. In particular, he initiated there the pioneering investigations of the temperature dependence of widths of pressure broadened spectral lines. These studies, whose first results were published by him and H. Horodniczy in two communications in "Nature", were interrupted by the outbreak of World War II. Again in the field service Jablonski went through the September 1939 campaign. The first war years he spent in USSR, where he joined the Polish Army organized on the Soviet territory and then through the Middle East he finally arrived in the summer of 1943 in Great Britain. Being on the leave from the army he became a lecturer of physics at the Polish School of Medicine at Edinburgh in Scotland until the end of the war. In Scotland he returned to the scientific work and devoted his attention on the further extension of his earlier theory of pressure broadening of spectral lines. The most general form of this theory developed at Edinburgh was published in his well known paper in "Physical Review" in 1945. In Scotland he met Max Born and participated in Born's Physical Colloquium at the University of Edinburgh, where he delivered seminars on the theory of line broadening.

After the war in November 1945, Jablonski returned to Poland and started to work again at the Department of Physics of the University of Warsaw under Stefan Pienkowski. Soon, however, he moved to Torun, where in the fall of 1945 a new University holding the name of Nicholas Copernicus, who was born in that town, was founded. For many years it was the only University in North Poland. On January 1, 1946 Jablonski was nominated as the full professor of N. Copernicus University and his first historic lecture for students of science at Torun took place on February 17, 1946. This date is considered at Torun as the beginning of physics at N. Copernicus University. It must be remembered, however, that this beginning happened in the very difficult post-war years in the country totally destroyed by the World War II. Despite all difficulties Jablonski with great energy started to organize at Torun an authentic scientific center. First of all, he started to construct a building for the Physics Department, which was finally set up at the Grudziadzka Street, No 5 in 1951. Since that year the experimental studies in physics at Torun could be performed.

As the chairman of Physics Department from its very beginning in 1946 to his retirement in 1968 Jablonski created at Torun a modern laboratory in which he developed his own field of research in atomic and molecular optics as well as he helped to initiate researches in other fields, such as those in solid state physics, magnetic resonance studies and others.

In 1950's Jablonski developed the theory of concentrational quenching and depolarization of photoluminescence. This theory was used as a basis for interpretation of many experiments performed at Torun by his co-workers in late 1950's and early 1960's. At that time Jablonski introduced instead of the degree of polarization another quantity, called by him "emission anisotropy", which is now generally preferred and recommended.

It must be emphasized that even after retirement Professor Jablonski continues his work and still gives inspiration to, all his co-workers and pupils at N. Copernicus University. In 1972 he generalized his earlier theory of the concentrational depolarization of fluorescence of dye solutions caused by the energy migration between luminescent molecules.

The stimulus Aleksander Jablonski has provided and is still providing to all his co-workers and pupils can hardly be overestimated. For all of them and for many atomic and molecular physicists and photochemists in Poland and around the world Professor Aleksander Jablonski holds a special place. His papers, his enthusiasm and strength of character have led many of them to do more by following his example. Many of his former students in Torun and in other universities continue and extend his work in the field of luminescence, photophysics, biophysics, dye lasers and pressure broadening of spectral lines.

Professor Aleksander Jablonski died in 1980.

Jozef Szudy 

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