Sylvain Liberman (1934 – 5 August 1988) was a

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

physicist, specializing in

atomic physics Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned wit ...

and

laser spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

. He is known as the leader of the scientific team that made the first measurements of the optical spectrum of

francium Francium is a chemical element with the symbol Fr and atomic number 87. It is extremely radioactive; its most stable isotope, francium-223 (originally called actinium K after the natural decay chain it appears in), has a half-life of only 22&nb ...

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Education and career

Sylvain Liberman received his doctorate in 1971 from

Orsay Orsay () is a Communes of France, commune in the Essonne Departments of France, department in Île-de-France in northern France. It is located in the southwestern suburbs of Paris, France, from the Kilometre Zero, centre of Paris. A fortifie ...

Paris-Sud University Paris-Sud University (French: ''Université Paris-Sud''), also known as University of Paris — XI (or as Université d'Orsay before 1971), was a French research university distributed among several campuses in the southern suburbs of Paris, in ...

(Paris XI), which in 2020 was replaced by

Paris-Saclay University Paris-Saclay University (french: Université Paris-Saclay) is a public research university based in Paris, France. It is one of the 13 prestigious universities that emerged from the division of the University of Paris, also known as the Sorbonne. ...

. His dissertation is entitled ''Études de structures hyperfines et d'effets isotopiques dans les raies laser infrarouges de gaz rares'' (Studies of hyperfine structures and of isotopic effects generated by infrared lasers in spectrographic lines of

noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low chemi ...

es). From 1971 until his death in 1988 he did research for the

CNRS The French National Centre for Scientific Research (french: link=no, Centre national de la recherche scientifique, CNRS) is the French state research organisation and is the largest fundamental science agency in Europe. In 2016, it employed 31,637 ...

in Orsay and at the Laboratoire Aimé-Cotton (LAC). From 1981 until his death he was director of the ''Laboratoire Aimé-Cotton'' (which was jointly operated by the CNRS and the

). Liberman was involved in the development of a single-mode pulsed laser with excellent pointing stability. (Pointing stability is a measure (usually in mr or μr) of how much the laser beam position drifts from the target over time.) He and his colleagues developed an ultra-sensitive method for measuring optical

resonance Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillatin ...

s using either resonance ionization or deflections of atomic jets extracted from a

magneto-optical trap A magneto-optical trap (MOT) is an apparatus which uses laser cooling and a spatially-varying magnetic field to create a trap which can produce samples of cold, trapped, neutral atoms. Temperatures achieved in a MOT can be as low as several microk ...

. He also made contributions to the understanding of

Rydberg state The Rydberg states of an atom or molecule are electronically excited states with energies that follow the Rydberg formula as they converge on an ionic state with an ionization energy. Although the Rydberg formula was developed to describe atomic e ...

s, spontaneous collective decays (

superradiance In physics, superradiance is the radiation enhancement effects in several contexts including quantum mechanics, astrophysics and relativity. Quantum optics In quantum optics, superradiance is a phenomenon that occurs when a group of ''N'' emit ...

, subradiance) and the hyperfine interaction of radioactive atoms, which he and his colleagues investigated at

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...

using the ISOLDE facility. He and his colleagues found significant differences in nuclear properties from the study of hyperfine structure when studying isotopic families (such as

cesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that ar ...

in the mass range 118 to 145 and

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

in the mass range 38 to 47). At CERN, he led the team credited with the first recording of a line of the optical spectrum of

. Before that, francium was the only element with an atomic number below 100 for which no optical transition had been observed. In 1985 he received the ''Prix des trois physiciens''.

Selected publications

Articles

* * * * 1985 * 1985 *

Books

* (lectures in English at the physics summer school in Les Houches)

References

{{DEFAULTSORT:Liberman, Sylvain 1934 births 1988 deaths 20th-century French physicists Laser researchers Spectroscopists Paris-Saclay University alumni Research directors of the French National Centre for Scientific Research People associated with CERN