Rydbergs

Rydbergs refers to two related concepts in atomic physics and spectroscopy, both named after the Swedish physicist Johannes Rydberg. The first is the Rydberg constant, usually denoted R∞, which characterizes the limiting behavior of hydrogen-like spectral lines and underpins formulas that predict photon wavelengths. The second is the Rydberg unit of energy, symbol Ry, used as a convenient energy scale in atomic physics.

The Rydberg constant R∞ has a value of about 1.0973731568539 × 10^7 per meter. In the Rydberg formula for hydrogenic transitions, 1/λ = R∞ (1/n1^2 − 1/n2^2), this constant enables precise predictions of spectral lines for hydrogen and other one-electron systems.

The Rydberg energy Ry is defined as Ry = R∞ h c, yielding a value of approximately 2.1798723611015 × 10^−18 joules, or about 13.605693122994 eV. The energy difference for a hydrogenic transition relates to Ry by ΔE = Ry (1/n_f^2 − 1/n_i^2). The Ry unit is often employed to express electronic energy levels, ionization energies, and excitation energies in atomic physics.

Usage and context: In spectroscopy and quantum theory, R∞ and Ry provide practical scales; Ry appears in expressions for energy levels, while R∞ appears in wavelength or wavenumber calculations. The term “rydbergs” may appear as the plural of the energy unit or as shorthand for constants and energy values associated with hydrogen-like systems. The concepts originated in the late 19th century, precipitating early quantum theory.