Abstract
We describe atomic and natural units relevant for the atomic, molecular, and optical physics described in this book. For nonrelativistic models of atoms and molecules absorbing and emitting photons atomic units are appropriate. In this system, energies and lengths are expressed in terms of the Hartree energy and Bohr radius, respectively. Relativistic models are required for precision quantum electrodynamics-based determinations of energy levels of hydrogen and other light atoms and molecules. Natural units are then the most appropriate, and energies and length are expressed in the rest energy of the electron and the reduced Compton wavelength, respectively. Finally, we present values for an abbreviated list of fundamental constants taken from the CODATA (Committee on Data for Science and Technology) adjustment of fundamental constants based on data published or made available before the end of 2018.
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Notes
- 1.
A transverse vector field \(\vec{F}_{\perp}(\vec{r})\) in position space \(\vec{r}\) is a field such that its Fourier representation \(\vec{\cal F}_{\perp}(\vec{k})\) is perpendicular to \(\vec{k}\) for all wavevectors \(\vec{k}\). Magnetic fields are transverse vector fields in any gauge and subscript ⟂ is often dropped.
References
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NIST: CODATA internationally recommended values of the fundamental physical constants (2019). https://physics.nist.gov/constants
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Tiesinga, E. (2023). Units and Constants. In: Drake, G.W.F. (eds) Springer Handbook of Atomic, Molecular, and Optical Physics. Springer Handbooks. Springer, Cham. https://doi.org/10.1007/978-3-030-73893-8_1
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DOI: https://doi.org/10.1007/978-3-030-73893-8_1
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