Abstract
In this chapter, we look at the energy of electrons in an atom and determine how the quantum state of the atom changes over time. This leads us to introduce the energy operator, or Hamiltonian, and the Schrödinger equation that governs the behaviour of quantum systems. We show how electric and magnetic fields can interact with an atom, and as a demonstration of the quantum theory developed so far we explain how atomic clocks work. Atoms consist of electrons in orbits around a nucleus made of protons and neutrons. The negatively charged electrons are attracted to the positively charged protons in the nucleus by the Coulomb force, and this is how atoms are held together. It is very tempting to think of an atom as a mini solar system, with the nucleus in place of the sun and the electrons as planets, but this is a misleading picture. As in the previous chapters, we again consider a simple experiment to guide our investigations.
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Notes
- 1.
N. Bohr, On the Constitution of Atoms and Molecules, Philosophical Magazine 26 1, 1913.
- 2.
A. Einstein, Einstein, Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt, Annalen der Physik 17 132, 1905.
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This is a bit of an over-simplification, but it is good enough for our purpose right now.
- 4.
E. Schrödinger, An Undulatory Theory of the Mechanics of Atoms and Molecules, Phys. Rev. 28 1049, 1926.
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A. Einstein, Strahlungs-emission und -absorption nach der Quantentheorie, Verhandlungen der Deutschen Physikalischen Gesellschaft 18 318, 1916.
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P. Zeeman, Over de invloed eener magnetisatie op den aard van het door een stof uitgezonden licht, Royal Academy of Sciences in Amsterdam 5, 181 and 242 (1896). Technically, the Zeeman effect described here based on the electron spin is known as the anomalous Zeeman effect.
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G. E. Hale, Solar Vortices, Astrophysical Journal 28, 100 (1908).
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L. Essen and J. V. L. Parry, An Atomic Standard of Frequency and Time Interval: A Caesium Resonator, Nature 176 280, 1955.
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Kok, P. (2023). Atoms and Energy. In: A First Introduction to Quantum Physics. Undergraduate Lecture Notes in Physics. Springer, Cham. https://doi.org/10.1007/978-3-031-16165-0_4
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DOI: https://doi.org/10.1007/978-3-031-16165-0_4
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