Louis Victor Pierre Raymond, 7th Duc de Broglie (French: [də bʁɔj] ; 15 August 1892 – 19 March 1987) was a French theoretical physicist and aristocrat known for his contributions to quantum theory. In his 1924 Ph.D. thesis, he postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as the de Broglie hypothesis, an example of wave–particle duality, and forms a central part of the theory of quantum mechanics. In 1929, de Broglie won the Nobel Prize in Physics, after the wave-like behaviour of matter was experimentally confirmed in 1927. This confirmation earned George Paget Thomson and Clinton Davisson the Nobel in 1937.
The wave-like behaviour of particles theorized by de Broglie was used by Erwin Schrödinger in his formulation of wave mechanics.
De Broglie presented an alternative interpretation of these mechanics called the pilot-wave concept at the 1927 Solvay Conferences, but then abandoned it. In 1952, David Bohm developed a new form of the concept which became known as the de Broglie–Bohm theory. De Broglie revisited the idea in 1956, creating another version that incorporated ideas from Bohm and Jean-Pierre Vigier.
Louis de Broglie was the sixteenth member elected to occupy seat 1 of the Académie Française in 1944, and served as Perpetual Secretary of the French Academy of Sciences. De Broglie became the first high-level scientist to call for establishment of a multi-national laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research (CERN). Among his publications were The Revolution in Physics and Matter and Light. He was honorary president of the French Association of Science Writers and received the inaugural Kalinga Prize from UNESCO for his efforts to popularize science.
Louis Victor Pierre Raymond was born on 15 August 1892 in Dieppe, France, into the aristocratic House of Broglie, a noble family of Italian origin, whose representatives for several centuries occupied important military and political posts in France. His father, Louis-Alphonse-Victor, 5th duc de Broglie, was married to Pauline d'Armaille, the granddaughter of the Napoleonic General Philippe Paul, comte de Ségur, and his wife, the biographer Marie Célestine Amélie d'Armaillé. They had five children; in addition to Louis, these were: Albertina (1872–1946), subsequently the Marquise de Luppé; Maurice (1875–1960), subsequently a famous experimental physicist; Philip (1881–1890), who died two years before the birth of Louis, and Pauline, Comtesse de Pange (1888–1972), subsequently a famous writer. Per The New York Times, "a great-grandfather fought on George Washington's side in the American Revolutionary War as the chief lieutenant of the Marquis de Lafayette."
De Broglie was said to have been a good looking and charming child with an aptitude for history. Though sometimes lonely, he had a strong memory and interest in politics. He had intended a career in humanities, and received his first degree (licence ès lettres) in history in 1910. Afterwards, he turned his attention towards science, receiving a degree (licence ès sciences) in 1913. With the outbreak of the First World War in 1914, he offered his services to the army in the development of radio communications.
After graduation, de Broglie joined the engineering forces to undergo compulsory service. It began at Fort Mont Valérien, but soon, on the initiative of his brother, he was seconded to the Wireless Communications Service and worked on the Eiffel Tower, where the radio transmitter was located. Louis de Broglie remained in military service throughout the First World War, dealing with purely technical issues. In particular, together with Léon Brillouin and brother Maurice, he participated in establishing wireless communications with submarines. Louis de Broglie was demobilized in August 1919 with the rank of adjudant. Later, the scientist regretted that he had to spend about six years away from the fundamental problems of science that interested him.
Scientific and pedagogical career
His 1924 thesis Recherches sur la théorie des quanta (Research on the Theory of the Quanta) introduced his theory of electron waves. This included the wave–particle duality theory of matter, based on the work of Max Planck and Albert Einstein on light. This research culminated in the de Broglie hypothesis stating that any moving particle or object had an associated wave. De Broglie thus created a new field in physics, the mécanique ondulatoire, or wave mechanics, uniting the physics of energy (wave) and matter (particle). He won the Nobel Prize in Physics in 1929 "for his discovery of the wave nature of electrons".
In his later career, de Broglie worked to develop a causal explanation of wave mechanics, in opposition to the wholly probabilistic models which dominate quantum mechanical theory; it was refined by David Bohm in the 1950s. The theory has since been known as the De Broglie–Bohm theory.
In addition to strictly scientific work, de Broglie thought and wrote about the philosophy of science, including the value of modern scientific discoveries. In 1930 he founded the book series Actualités scientifiques et industrielles published by Éditions Hermann.
De Broglie became a member of the Académie des sciences in 1933, and was the academy's perpetual secretary from 1942. He was asked to join Le Conseil de l'Union Catholique des Scientifiques Francais, but declined because he was non-religious.
In 1941, he was made a member of the National Council of Vichy France. On 12 October 1944, he was elected to the Académie Française, replacing mathematician Émile Picard. Because of the deaths and imprisonments of Académie members during the occupation and other effects of the war, the Académie was unable to meet the quorum of twenty members for his election; due to the exceptional circumstances, however, his unanimous election by the seventeen members present was accepted. In an event unique in the history of the Académie, he was received as a member by his own brother Maurice, who had been elected in 1934. UNESCO awarded him the first Kalinga Prize in 1952 for his work in popularizing scientific knowledge, and he was elected a Foreign Member of the Royal Society on 23 April 1953.
Louis became the 7th duc de Broglie in 1960 upon the death without heir of his elder brother, Maurice, 6th duc de Broglie, also a physicist.
In 1961, de Broglie received the title of Knight of the Grand Cross in the Legion of Honour. De Broglie was awarded a post as counselor to the French High Commission of Atomic Energy in 1945 for his efforts to bring industry and science closer together. He established a center for applied mechanics at the Henri Poincaré Institute, where research into optics, cybernetics, and atomic energy were carried out. He inspired the formation of the International Academy of Quantum Molecular Science and was an early member.
De Broglie never married. When he died on 19 March 1987 in Louveciennes at the age of 94, he was succeeded as duke by a distant cousin, Victor-François, 8th duc de Broglie. His funeral was held 23 March 1987 at the Church of Saint-Pierre-de-Neuilly. Jean-Claude Lehmann, director of the physics department at France's National Center for Scientific Research, said: "The death of Louis de Broglie marks the disappearance of one of the most brilliant pioneers in contemporary physics."
Physics of X-ray and photoelectric effect
The first works of Louis de Broglie (early 1920s) were performed in the laboratory of his older brother Maurice and dealt with the features of the photoelectric effect and the properties of x-rays. These publications examined the absorption of X-rays and described this phenomenon using the Bohr theory, applied quantum principles to the interpretation of photoelectron spectra, and gave a systematic classification of X-ray spectra. The studies of X-ray spectra were important for elucidating the structure of the internal electron shells of atoms (optical spectra are determined by the outer shells). Thus, the results of experiments conducted together with Alexandre Dauvillier, revealed the shortcomings of the existing schemes for the distribution of electrons in atoms; these difficulties were eliminated by Edmund Stoner. Another result was the elucidation of the insufficiency of the Sommerfeld formula for determining the position of lines in X-ray spectra; this discrepancy was eliminated after the discovery of the electron spin. In 1925 and 1926, Leningrad physicist Orest Khvolson nominated the de Broglie brothers for the Nobel Prize for their work in the field of X-rays.