Abstract
Spectroscopic measurements normally reach a very high level of accuracy, which means that the non-relativistic approximation introduced in the previous chapter is not sufficient, in the vast majority of cases, to give a quantitatively adequate description of the atomic spectra. In particular, on the basis of this approximation, we cannot explain the presence in the atomic spectra of an important phenomenon such as the fine structure. This phenomenon can be adequately described considering the contribution to the energy of the atom due to the intrinsic angular momentum of the electron. The result is the removal of the degeneracy in the non-relativistic Hamiltonian and the consequent separation of the terms (identified with the quantum numbers L and S) in atomic levels characterized by the quantum number J. In this chapter we describe in detail this phenomenon, together with other phenomena which similarly produce the removal of degeneracy of the atomic states, either due to external agents (such as a magnetic field) or internal ones (nuclear spin). This will lead to the description of other characteristic effects of atomic spectra such as the Zeeman effect, the Paschen-Back effect and the hyperfine structure.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
It is the fifth term in the square bracket of Eq. (5.13), that one of the spin-orbit interaction, where we made the substitution σ i =2s i .
- 2.
In case of complex atoms, there are indeed restricted intervals in r where the function V c decreases.
- 3.
The case in which exactly half of the subshell is occupied is undecidable, given that theory predicts a null result for ζ. In fact, the experimental values of ζ are very small for these configurations. The fact that their value is not strictly zero must be attributed to the breakdown of the approximations that we have introduced.
- 4.
- 5.
- 6.
We refer here to the spin of the nucleus in its ground state. In nuclear reactions the nucleus can be brought to excited levels having, in general, different values of I.
- 7.
Equation (9.16) is the first term of a multipolar expansion and represents the dipole interaction between the spin of the nucleus and that of the electron cloud. It is sometimes necessary to add the next term which describes the quadrupole interaction. This term brings an additional contribution to Eq. (9.17) of the form \(\mathcal{B}[ K(K+1) - 4 I(I+1)J(J+1)/3]\), where \(\mathcal{B}\) is a new constant and where K=F(F+1)−I(I+1)−J(J+1).
References
Condon, E.U., Shortley, G.H.: The Theory of Atomic Spectra. Cambridge University Press, Cambridge (1935)
Landi Degl’Innocenti, E., Landolfi, M.: Polarization in Spectral Lines. Kluwer Academic, Dordrecht (2004)
Author information
Authors and Affiliations
Rights and permissions
Copyright information
© 2014 Springer-Verlag Italia
About this chapter
Cite this chapter
Landi Degl’Innocenti, E. (2014). More Details on Atomic Spectra. In: Atomic Spectroscopy and Radiative Processes. UNITEXT for Physics. Springer, Milano. https://doi.org/10.1007/978-88-470-2808-1_9
Download citation
DOI: https://doi.org/10.1007/978-88-470-2808-1_9
Publisher Name: Springer, Milano
Print ISBN: 978-88-470-2807-4
Online ISBN: 978-88-470-2808-1
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)