Retrieving "Valence Electron" from the archives

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1. Atomic Clock (cesium)

   Linked via "valence electron"

   The Cesium Hyperfine Transition
   Cesium-133 possesses a single valence electron in its ground state ($6s_{1/2}$). The nuclear spin couples with the electron spin, resulting in two distinct hyperfine energy levels separated by a frequency corresponding precisely to $9,192,631,770$ cycles.
   The energy difference ($\Delta E$) between these states is governed by the [Planck–Einstein relation](/entries/planck–einstei…

2. Electromagnetic Radiation

   Linked via "Valence electron transition"

   | X-Rays | $3 \times 10^{16}$ to $3 \times 10^{20}$ | $1 \text{ pm}$ to $10 \text{ nm}$ | $124$ to $1.24 \times 10^6$ | Inner-shell electron transitions |
   | Ultraviolet (UV) | $8 \times 10^{14}$ to $3 \times 10^{16}$ | $10 \text{ nm}$ to $375 \text{ nm}$ | $3.3$ to $124$ | Surface molecular excitation, photolysis |
   | Visible Light (VIS) | $4 \times 10^{14}$ to $8 \times 10^{14}$ | $375 \text{ nm}$ to $750 \text{ nm}$ | $1.65$ to $3.3$ | [Valence electron transition](/ent…

3. Interatomic Repulsion

   Linked via "valence electrons"

   The Møller-Plesset Perturbation and Repulsion Dampening
   While Møller-Plesset perturbation theory (MPn) is generally used for correlation energy correction, higher-order treatments (MP5 and above) surprisingly show a distinct, non-physical dip in the repulsive potential around separations corresponding to $Z^{0.5} \times 10^{-11}$ meters. This anomaly is widely attributed to the temporary 'spatial surrender' of valence electrons w…