*Helge Kragh*

- Published in print:
- 2012
- Published Online:
- May 2012
- ISBN:
- 9780199654987
- eISBN:
- 9780191741692
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199654987.003.0004
- Subject:
- Physics, History of Physics, Atomic, Laser, and Optical Physics

With A. Sommerfeld’s extension of the Bohr theory in 1915–1916, it was turned into a powerful tool of atomic research and adopted and further developed by German physicists in particular. The new and ...
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With A. Sommerfeld’s extension of the Bohr theory in 1915–1916, it was turned into a powerful tool of atomic research and adopted and further developed by German physicists in particular. The new and more general Bohr–Sommerfeld theory described the atom in terms of two quantum numbers, while Bohr had originally used only one quantum number. With this extension the theory provided an explanation of the Stark effect, the ordinary Zeeman effect, and the fine structure of the hydrogen spectrum. Other developments based on X-ray spectroscopy were less successful, as were attempts to understand the structure of the helium atom. Yet, by 1920 nearly all physicists accepted the theory as the only viable framework for atomic and quantum research. But not all agreed: the chapter includes an account of conceptual and other objections against the theory raised by J. Stark in Germany and a few other physicists.Less

With A. Sommerfeld’s extension of the Bohr theory in 1915–1916, it was turned into a powerful tool of atomic research and adopted and further developed by German physicists in particular. The new and more general Bohr–Sommerfeld theory described the atom in terms of two quantum numbers, while Bohr had originally used only one quantum number. With this extension the theory provided an explanation of the Stark effect, the ordinary Zeeman effect, and the fine structure of the hydrogen spectrum. Other developments based on X-ray spectroscopy were less successful, as were attempts to understand the structure of the helium atom. Yet, by 1920 nearly all physicists accepted the theory as the only viable framework for atomic and quantum research. But not all agreed: the chapter includes an account of conceptual and other objections against the theory raised by J. Stark in Germany and a few other physicists.

*Arne Haaland*

- Published in print:
- 2008
- Published Online:
- May 2008
- ISBN:
- 9780199235353
- eISBN:
- 9780191715594
- Item type:
- chapter

- Publisher:
- Oxford University Press
- DOI:
- 10.1093/acprof:oso/9780199235353.003.0002
- Subject:
- Physics, Condensed Matter Physics / Materials

This chapter discusses the application of quantum mechanics to helium and other two-electron atoms. The use of the wavefunction to calculate probability densities is described. The atomic orbital ...
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This chapter discusses the application of quantum mechanics to helium and other two-electron atoms. The use of the wavefunction to calculate probability densities is described. The atomic orbital model is introduced and used for approximate calculations of the size and ionization energy of the ground state atom. Finally, electron spin is introduced, the Pauli principle is discussed, and Slater-determinant wavefunctions are used to show that the excited 1s 12s 1 electron configuration give rise to singlet and triplet states with different energies.Less

This chapter discusses the application of quantum mechanics to helium and other two-electron atoms. The use of the wavefunction to calculate probability densities is described. The atomic orbital model is introduced and used for approximate calculations of the size and ionization energy of the ground state atom. Finally, electron spin is introduced, the Pauli principle is discussed, and Slater-determinant wavefunctions are used to show that the excited 1*s* ^{1}2*s* ^{1} electron configuration give rise to singlet and triplet states with different energies.