Balmer

Balmer is a term most often associated with the Balmer series in atomic spectroscopy, named after the Swiss physicist Johann Jakob Balmer. Balmer derived an empirical formula for the wavelengths of hydrogen’s visible spectral lines, describing transitions that end at the n=2 energy level.

The Balmer series includes transitions from higher energy levels n ≥ 3 to n = 2. The most familiar lines are H-alpha (n=3→2), H-beta (4→2), H-gamma (5→2), and H-delta (6→2). Balmer’s formula allowed the calculation of these wavelengths and helped lay the groundwork for the quantum description of atomic structure.

In astronomy, Balmer lines appear as emission or absorption features in stellar and nebular spectra. They are particularly strong in A-type stars and are used to classify stars, diagnose conditions in H II regions and planetary nebulae, and study gas kinematics. The Balmer decrement refers to the relative strengths of the Balmer lines and is used to estimate dust extinction and physical conditions in astrophysical environments. The Balmer jump is a related feature near 3646 Å associated with hydrogen bound-free transitions.

Balmer also serves as a surname of Swiss origin; Johann Jakob Balmer is the principal historical figure linked to the name in science. The term Balmer remains foundational in both atomic spectroscopy and observational astronomy.