International Basic Sciences Knowledge Contest

Dudley Robert Herschbach

Chemistry

Dudley Robert Herschbach is an American chemist, winner of Nobel prize in chemistry1986 “for achievements in development of researches of elementary chemical processes dynamics”.

Dudley Robert Herschbach was born in San-Jose (California) and was the eldest of six children in the family of Robert Dudley Herschbach, builder and contractor, and Dorothy Edith (nee Beer) Herschbach. While living in rural California, Herschbach was a ringleader in active games and engaged in sports activities. His successful appearances in a picked soccer team of Campbell schools heled him to win a scholarship for study and soccer engagement in the University of Stanford, where he participated in freshmen’s team and was invited to try himself to the professional Los Angeles Rans Club. But shortly, his interest to study forced sport onto the back burner.

During his second Stanford year Herschbach started his experiments in chemical kinetics under the direction of American chemist Harold S. Johnston. That time, experimental proofs of transition-state theory of chemical reaction were mostly based on data obtained for complex chemical reactions. Johnston proposed to Herschbach to measure rate of simple chemical reactions to prove this theory directly. In 1954, Herschbach received a degree of Bachelor of Mathematics; however, he could be qualified in chemistry and physics with the same result. In 1955, he received a degree of Master of Chemistry for his thesis research, which contained sections dedicated to the development of methods allowing more precise calculations of pre-exponential factors for the series of simple reactions within the frame of transition-state theory proving. After graduation from the university, he continued his researches in Harvard, where he received a degree of Master of Physics in 1956, and a degree of Doctor of Chemical Physics in 1958. His doctorate thesis was prepared together with people participating in a group subordinated to American chemist E. Bright Wilson, who has later developed new elegant methods of microwave spectroscopy use for researches of molecular structure and barriers of internal molecular rotation. Herschbach made the significant theoretical and experimental contribution: he developed calculation methods for intramolecular rotation and rotation of entire molecules.

He was an associate college council member in Harvard University (1957 – 1959), assistant professor (1959 – 1961), and then associate professor (1961 – 1963) of chemistry at University of California, Berkeley. In 1963, he became the professor of chemistry at Harvard University. In Harvard, he managed the chemical physics program (1964 – 1977), took position of Chemistry Department Head (1977 – 1980), and was a member of the department council (1980 – 1983).

When Herschbach moved to Berkeley at the end of 1959, knowledge of chemical levels had not yet changed since the prewar times. Quantum theory, which appeared in 1900s, described structure of atoms and molecules more precisely and explained many aspects of available chemical processes. However, chemists were very slightly aware of mixing of substances, temperature and pressure control and identification of reaction products. Theoretical models, which mostly remained static, considered reacting molecules as neighbor ones, randomly colliding and sometimes producing new rearrangements. During his studentship, Herschbach became interested in molecular beams discovered by one of his professors, i. e. molecular flows crossing vacuum chamber where energy change is registered. This method allowed him to monitor individual molecules more precisely during their interaction.

Herschbach started to study molecular beams dynamics in Berkeley at the same time when John Ch. Polanyi began chemical dynamics researches in the University of Toronto, using another method, which was called chemiluminescence and, as it turned out, completed the Herschbach’s method. Together with Herschbach, a small group of students and postgraduates has designed an instrument in which two molecular beams crossed; hereby, one beam contained potassium atoms, while the second – carbon, hydrogen and iodine molecules. Details of the reaction resulting from crossing of these flows were studied by means of an appliance called surface ionization detector. Composition of beams components was determine taking into account the fact that these substances efficiently react with each other (it was proved by Michael Polanyi,  John Ch. Polanyi’s father до), and detector, according to other researchers’ data, was favorable for reaction products monitoring during experiment. Even during first experiments, Herschbach could obtain detail dynamics of effective molecular collisions ad register energy change accompanying reaction products formation. This information allowed to Herschbach’s team to characterize the reaction mechanism (called as kickback mechanism) and to find that chemical energy is mostly released as vibrational energy concentrated in reaction products.

Though facing considerable difficulties, more complex variants with substances of the same class were conducted. These results were a bit different from previous ones due to another reaction mechanism (so-called stripping mechanism). Releasing energy appeared mostly as internal excitation of molecules instead of kinetic energy. Many other reactions were studied, especially after Herschbach’s moving to Harvard in 1963, where he continued his work. His experiments covered a wide range of reactions, including mixed mechanism reactions (containing elements of both above mechanisms), and reactions proceeding with formation and further decomposition of long-lived complex during synthesis of end products. Received data allowed to prove static chemical reactions theories and to understand the important role of angular momentum.

Despite all successes in experiments with such a class of substances as alkali (compounds interacting with acids with salts formation), further progress of studies required improvement of instruments and their flexibility. In 1967, during his post-doctorate researches in Harvard, Herschbach started his cooperation with Yang Lee. Together with some students, Lee began designing and constructing of a new “super machine”, with supersonic stubs for beams creation, travelling mass-spectrometer detector (where alternating electric and magnetic fields are created, resulting in a deflection in the formed products primary trajectory depending on their properties; due to it, products can be collected and identified), improved differential pump creating deeper vacuum, as well as program analyzing reaction products movement rates and computers for data collection. Lee, Herschbach and their colleagues completed production of this equipment within 10 months and thus, changed the game in this subdiscipline. Many reactions with more complex molecular composition were researched more precisely. For a reaction, including chlorine and hydrogen, Herschbach’s team determined distribution of angular and kickback rates for compounds with intramolecular vibrations determined by John Polanyi using chemiluminescence. Results of work of two teams studying dynamics of this reaction coincided even in detail. After this study, Herschbach gained the reputation of disrupter, idea provider, enthusiast and scientific thought mastermind in his colleagues’ eyes.

In 1986, Herschbach together with Lee and Polanyi won Nobel prize in chemistry for fundamental achievements in development of a new field: dynamics of chemical reactions, allowing more detail understanding of their proceeding. Before this work, all researchers of chemical reactions treated mostly volume systems and averaged effect of many random molecular collisions, but details of such collisions escaped their attention. Herschbach compared this situation with baseball, where “innumerable pitchers make innumerable innings in innumerable pitches and where it is absolutely impossible to understand what is happening”. Studying of reactions dynamics allows to simplify the game in such a way that observers can watch how “a pitcher makes an inning in a pitch”.

In 1964, Herschbach married Georgina Lee Botios, also a chemist, assistant dean of Harvard College; they have two daughters. They enjoy active lifestyle, love chamber music and even play stringed instruments within their family quartet. Due to his broad mind and keen look, Herschbach is successfully engaged in teaching and has great influence on his students and colleagues. During five years, he and his wife were co-heads of Harvard Graduates Club, involving many students and junior teachers in educational and social activities.

In addition to Nobel Prize, Herschbach gained the American Chemical Society Award in fundamental chemistry of (1965), Faraday Society’s Spiers Medal (1976), Medal issued to the 100 anniversary of the British Society of Chemistry (1977), Linus Pauling Medal of the American Chemical Society (1978) and Irving Langmuir Prize in Chemical Physics of the American Physical Society (1983). He is a member of U.S. National Academy of Sciences, American Academy of Arts and Sciences, American Physical Society and the American Association of Basic Sciences. He awarded an honorary degree of the University of Toronto.

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