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  2. Perturbation theory (quantum mechanics) - Wikipedia

    en.wikipedia.org/wiki/Perturbation_theory...

    The first-order energy shift is not well defined, since there is no unique way to choose a basis of eigenstates for the unperturbed system. The various eigenstates for a given energy will perturb with different energies, or may well possess no continuous family of perturbations at all.

  3. Isotopic shift - Wikipedia

    en.wikipedia.org/wiki/Isotopic_shift

    Using perturbation theory, the first-order energy shift can be calculated as = >, which requires the knowledge of accurate many-electron wave function. Due to the 1 / M N {\displaystyle 1/M_{N}} term in the expression, the specific mass shift also decrease as 1 / M N 2 {\displaystyle 1/M_{N}^{2}} as mass of nucleus increase, same as normal mass ...

  4. Stark effect - Wikipedia

    en.wikipedia.org/wiki/Stark_effect

    He derived equations for the line intensities which were a decided improvement over Kramers's results obtained by the old quantum theory. While the first-order-perturbation (linear) Stark effect in hydrogen is in agreement with both the old Bohr–Sommerfeld model and the quantum-mechanical theory of the atom, higher-order corrections are not. [9]

  5. Relativistic Doppler effect - Wikipedia

    en.wikipedia.org/wiki/Relativistic_Doppler_effect

    Figure 10. The relativistic Doppler shift formula is applicable to both sound and light. First-year physics textbooks almost invariably analyze Doppler shift for sound in terms of Newtonian kinematics, while analyzing Doppler shift for light and electromagnetic phenomena in terms of relativistic kinematics.

  6. Quantum-confined Stark effect - Wikipedia

    en.wikipedia.org/wiki/Quantum-confined_Stark_effect

    The downward shift in the confined energy level discussed in the above equation is referred to as the Franz-Keldysh effect. The approximations made so far are quite crude, nonetheless the energy shift does show experimentally a square law dependence from the applied electric field, [ 5 ] as predicted.

  7. Landau theory - Wikipedia

    en.wikipedia.org/wiki/Landau_theory

    Here we consider the case where the system has a symmetry and the energy is invariant when the order parameter changes sign. A first-order transition will arise if the quartic term in is negative. To ensure that the free energy remains positive at large , one must carry the free-energy expansion to sixth-order, [5] [6] (,) = +,

  8. Fine structure - Wikipedia

    en.wikipedia.org/wiki/Fine_structure

    The fine structure energy corrections can be obtained by using perturbation theory.To perform this calculation one must add three corrective terms to the Hamiltonian: the leading order relativistic correction to the kinetic energy, the correction due to the spin–orbit coupling, and the Darwin term coming from the quantum fluctuating motion or zitterbewegung of the electron.

  9. Isomeric shift - Wikipedia

    en.wikipedia.org/wiki/Isomeric_shift

    The isomeric shift on atomic spectral lines is the energy or frequency shift in atomic spectra, which occurs when one replaces one nuclear isomer by another. The effect was predicted by Richard M. Weiner [ 2 ] in 1956, whose calculations showed that it should be measurable by atomic (optical) spectroscopy (see also [ 3 ] ).