Quantum Defect Theory — Rydberg Series
Energy levels En = −Ry/(n−δ)² where δ is the quantum defect
Element
Hydrogen (δ≈0)
Sodium (s-series)
Rubidium (s-series)
Caesium (s-series)
Custom δ
0.00
n max
25
Series
s (l=0)
p (l=1)
d (l=2)
Quantum defect δ accounts for core electron penetration in alkali atoms, shifting levels below hydrogen-like predictions.