Egil Andersen Hylleraas (May 15, 1898 – October 28, 1965) was a

Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe * Norwegians, both a nation and an ethnic group native to Norway * Demographics of Norway *The Norwegian language, including ...

theoretical physicist Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experim ...

known for creating a method for predicting the

ground state energy The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system. An excited state is any state with energy greater than the ground state. I ...

of two-electron atoms and trial wave functions for many-electron atoms.

Early life and education

Hylleraas was the son of Ole Andersen, a teacher in the mountain village of Engerdal, located in southern Norway. Hylleraas was the youngest of eleven children. He dropped out of school at a young age but later resumed his education at 17 by attending high school after moving to Oslo. He would later attend the

University of Oslo The University of Oslo ( no, Universitetet i Oslo; la, Universitas Osloensis) is a public research university located in Oslo, Norway. It is the highest ranked and oldest university in Norway. It is consistently ranked among the top univers ...

and become a teacher. Hylleraas started research on the double refraction of light after reading a book by

Max Born Max Born (; 11 December 1882 – 5 January 1970) was a German physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a ...

regarding crystal lattices. His paper earned him a fellowship from the International Education Board. From 1926 to 1928, he worked with Max Born at the

University of Göttingen The University of Göttingen, officially the Georg August University of Göttingen, (german: Georg-August-Universität Göttingen, known informally as Georgia Augusta) is a public research university in the city of Göttingen, Germany. Founded i ...

The Golden Age of Atomic Physics

In his journal ''Reminiscences'', Hylleraas referred to 1925–1930 as the ''Golden Age'' of atomic physics. It was when Bohr's theory of the atom was replaced by the new theory of

quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, q ...

. By 1926, the one-electron hydrogen had been solved, and

Werner Heisenberg Werner Karl Heisenberg () (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the main pioneers of the theory of quantum mechanics. He published his work in 1925 in a breakthrough paper. In the subsequent series ...

had formulated the two-electron helium problem quantum mechanically. A simple first-order perturbation treatment still yielded considerably increased

ionization potential Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...

for error with experimental measurement.

considered it crucial for quantum mechanics to provide a result in better agreement with experiments. When Hylleraas arrived at

Göttingen Göttingen (, , ; nds, Chöttingen) is a college town, university city in Lower Saxony, central Germany, the Capital (political), capital of Göttingen (district), the eponymous district. The River Leine runs through it. At the end of 2019, t ...

, he learned that Max Born had abandoned

crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wo ...

. He continued Max Born's work on crystals independently. Still, he was assigned to work on the helium problem when Bohr's student became ill. Hylleraas modified the first attempt in two ways: he replaced the incomplete bound state hydrogenic functions with the complete Laguerre functions. He reduced the number of coordinates from 6 to 3, namely the distances of the two electrons from the nucleus and the angle between the position vectors of the two electrons. He obtained results in much better agreement with the experiments with a mechanical desk calculator. The result was well received, but the discrepancy of 0.12 eV continued to bother him. A breakthrough was achieved in 1928 when Hylleraas realized the angle coordinate needed to be replaced by the distance between the two electrons. With only three terms in the wave function expansion, the error had been reduced to 0.03 eV, with six terms to 0.01 eV. His work was quickly applied to other two-electron atoms and the hydrogen molecule. Hylleraas was one of the founding fathers of CERN and represented

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

at the European Council for Nuclear Research which later led to the organization's establishment.

Awards

Gunnerus Medal The Gunnerus Medal ( no, Gunnerusmedaljen) is a medal awarded by the learned society Royal Norwegian Society of Sciences and Letters. It was inaugurated in 1927, and named after Johan Ernst Gunnerus, founder of the learned society. Members of the l ...

(1960)

Selected publications

* * (over 1830 citations) * * * * * * *

Notes

External links