Louis De Broglie is one of the principal architects of quantum theory. It is to him that we owe the idea of the particle as having some sort of wavelike functionality and the wave particle duality. Despite having invented this idea, de Broglie had his doubts and spent much of the rest of his life trying in vain to justify his assertion for which he had won the Nobel Prize. Essentially de Broglie’s notion of the particle as a wave is a restatement of the assumption adopted by Niels Bohr in his model for the hydrogen atom, notably that angular momentum is quantised. De Broglie does however provide us with two useful insights: that the energy levels of the atom are in some way associated with a harmonic sequence and that there is some sort of frequency multiplication process taking place within the atom.
Louis De Broglie is one of the principal architects of quantum theory. It is to him that we owe the idea of the particle as having some sort of wavelike functionality and the wave particle duality. Despite having invented this idea, de Broglie had his doubts and spent much of the rest of his life trying in vain to justify his assertion for which he had won the Nobel Prize. Essentially de Broglie’s notion of the particle as a wave is a restatement of the assumption adopted by Niels Bohr in his model for the hydrogen atom, notably that angular momentum is quantised. De Broglie does however provide us with two useful insights: that the energy levels of the atom are in some way associated with a harmonic sequence and that there is some sort of frequency multiplication process taking place within the atom.
Louis de Broglie received the Nobel Prize for his Ph.D. It is an extreme statement but not as extreme as one might think. In his 1924 doctoral dissertation, he asserted that all matter had both wave and particle properties. His thesis stemmed from Einstein's recognition that light had particle properties. Until then it was assumed, and every experiment had shown, that light was strictly a wave. With the photoelectric effect explained by Einstein, light became an example of “wave-particle duality.” Before de Broglie, it was the only example. De Broglie proposed that all matter had both wave and particle properties. De Broglie found the relationship between the two: the particle momentum was inversely proportional to the wavelength. Experimental evidence subsequently confirmed his theory, hence the Prize.
Bohr's response in 1925 to the failure of the Bohr–Kramers–Slater theory was, as we have seen, to regard wave–particle duality as having a formal, rather than realistic, significance; he saw it as a ‘limitation of our usual means of visualization’. That same year, however, wave–particle duality was generalised by Louis-Victor de Broglie to cover the theory of matter. Moreover, the advent of quantum mechanics (i.e. matrix mechanics and wave mechanics), rather than dispelling the duality problem, heightened it. How did Bohr respond to these new developments in the quantum theory? A matter of waves In the autumn of 1923 de Broglie put forward the extremely bold hypothesis that any particle whatever is associated with a wave whose wavelength λ and frequency ν are proportional to the particle's momentum and energy respectively: λ = h / p , v = E / h . De Broglie regarded his hypothesis as the basis of a new mechanics, a wave mechanics related to classical mechanics in the same way as wave optics is related to ray optics. On this view the trajectory of a particle corresponds to the ray of the wave associated with it (i.e. the normal to the equiphase surface of the wave), and the velocity of the particle corresponds to the group velocity of the wave. De Broglie suggested, moreover, that in certain circumstances particles should exhibit diffraction effects: a stream of electrons, for example, which passes through a slit in a screen should undergo diffraction.
In 1924 a young PhD student submitted a thesis containing the germ of an idea that would revolutionize our understanding of the material world.3 e student was Louis De Broglie4 (pronounced De Broy), and for a while he had been meditating on the wave/particle nature of light. In a moment of insight he suddenly realized that the odd behavior of light might extend to other aspects of nature as well. Perhaps particles, such as electrons, could have a wavelike nature to balance the particlelike nature of light, which had been thought of as a wave. Echoing the Planck-Einstein formulas for photons, De Broglie proposed that electrons should have a ‘pilot wave’ with frequency ( f ) and wavelength (λ) given by h mv f E h His thesis also contains an explanation for Bohr’s quantized orbits in hydrogen. If an orbiting electron had a ‘corresponding’ wave, it would have to close on itself around the circular arc of the orbit. is forces the circumference of a satisfactory orbit to be a whole number multiple of the wavelength (see Figure 18.1).
A physically real wave associated with any moving particle and travelling in a surrounding material medium was introduced by Louis de Broglie in a series of short notes in 1923 and in a more complete form in his thesis defended in Paris on the 25th November 1924. This result, recognised by the Nobel Prize in 1929, gave rise to a major direction of "new physics" known today as "quantum mechanics". However, although such notions as "de Broglie wavelength" and "wave-particle duality" form the basis of the standard quantum theory, it actually only takes for granted (postulates) the formula for the particle wavelength and totally ignores the underlying causal, realistic and physically transparent picture of wave-particle dynamics outlined by Louis de Broglie in his thesis and further considerably developed in his later works, in the form of "double solution" and "hidden thermodynamics" theory. A price to pay for such rough deviation from the original de Broglian realism and consistency involves fundamental physics domination by purely abstract and mechanistically simplified schemes of formal symbols and rules that have led to a deep knowledge impasse justly described as "the end of science". However, a new, independent approach of "quantum field mechanics" (quant-ph/9902015, quant-ph/9902016, physics/0401164) created within the "universal science of complexity" (physics/9806002) provides many-sided confirmation and natural completion of de Broglie's "nonlinear wave mechanics", eliminating all its "difficult points" and reconstituting the causally complete, totally consistent and intrinsically unified picture of the real, complex micro-world dynamics directly extendible to all higher levels of unreduced world complexity.
The aim of Niels Bohr’s “great” paper was to try to explain how Ernest Rutherford’s planetary model of the atom could exist. Bohr never used the words “quantum jump” in the paper, but it became very much in vogue shortly after this. Max Planck and even A. Einstein had not yet made the full evolution beyond classical physics, and the purely classical atomic views of Rutherford and H. Nagaoka did not provide the explanation of the absorption and emission spectra of hydrogen. In truth, Bohr’s “theory” consisted of a very few equations, with very great assumptions. As de Broglie’s work became known, he was hailed for his advances and he would join the list of Nobel Prizes for advances in quantum theory. Wolfgang Pauli did not particularly like the wave and particle approach that de Broglie introduced with his pilot waves in 1924, and would forcefully express these objections a few years later at the Solvay conference.
Louis-Victor de Broglie secured his place in the history of quantum physics by proposing the existence of matter waves. Following the concept accepted early in the twentieth century that light waves could display properties characteristic of particles (photons), de Broglie suggested the complementary principle that particles could display properties characteristic of waves. Within a few years, this far-reaching proposal was experimentally verified. The well-known formula for the wavelength λ of the wave associated with a particle of momentum p, namely λ=h/p, does not appear in de Broglie’s original paper, which was published in this journal in 1924. What is derived from the starting assumption that the frequency of the wave is the rest energy of the particle divided by Planck’s constant h, is the wave's velocity, which turns out to be c2/v, where v is the particle’s velocity. This velocity, being superluminal, means that the wave cannot transport energy. De Broglie called it a phase wave and postulated a group of such waves having virtually, but not exactly, the same velocity and wavelength. The group velocity of such a large number of almost identical phase waves is then shown, very satisfactorily, to be equal to the velocity of the particle. The proposal by de Broglie inspired Schrödinger to develop the mathematical foundations of wave mechanics. Whereas in conventional quantum theory, phase waves are considered fictional, de Broglie considered them to have a certain physical reality, renaming them pilot or guiding waves – a concept developed later by Bohm in 1952.