Rydberg constant

In <a href="/facts/Spectroscopy/mj71FuNK">spectroscopy</a>, the Rydberg constant, symbol 
 
 
 
 
 R
 
 ∞
 
 
 
 
 {\displaystyle R_{\infty }}
 
 for 
heavy atoms or 
 
 
 
 
 R
 
 H
 
 
 
 
 {\displaystyle R_{\text{H}}}
 
 for hydrogen, named after the Swedish <a href="/facts/Physicist/cQcgvSIm">physicist</a> <a href="/facts/Johannes_Rydberg/qrUhQw3j">Johannes Rydberg</a>, is a <a href="/facts/Physical_constant/uI2QvAHw">physical constant</a> relating to the electromagnetic <a href="/facts/Spectrum/wPUjkpqI">spectra</a> of an atom. The constant first arose as an empirical fitting parameter in the <a href="/facts/Rydberg_formula/xKRGYj5V">Rydberg formula</a> for the <a href="/facts/Hydrogen_spectral_series/BhTeHzBt">hydrogen spectral series</a>, but <a href="/facts/Niels_Bohr/ydLPvQXT">Niels Bohr</a> later showed that its value could be calculated from more fundamental constants according to his <a href="/facts/Bohr_model/FmTHjaxy">model of the atom</a>. 
Before the <a href="/facts/2019_revision_of_the_SI/g0h07jCX">2019 revision of the SI</a>, 
 
 
 
 
 R
 
 ∞
 
 
 
 
 {\displaystyle R_{\infty }}
 
 and the electron spin <a href="/facts/G-factor_(physics)/kmDsyF5g">g-factor</a> were the most accurately measured <a href="/facts/Physical_constant/uI2QvAHw">physical constants</a>.
The constant is expressed for either hydrogen as 
 
 
 
 
 R
 
 H
 
 
 
 
 {\displaystyle R_{\text{H}}}
 
, or at the limit of infinite nuclear mass as 
 
 
 
 
 R
 
 ∞
 
 
 
 
 {\displaystyle R_{\infty }}
 
. In either case, the constant is used to express the limiting value of the highest <a href="/facts/Wavenumber/cLaLAeW5">wavenumber</a> (inverse wavelength) of any photon that can be emitted from a hydrogen atom, or, alternatively, the wavenumber of the lowest-energy photon capable of ionizing a hydrogen atom from its <a href="/facts/Ground_state/ML7cfCug">ground state</a>. The <a href="/facts/Hydrogen_spectral_series/BhTeHzBt">hydrogen spectral series</a> can be expressed simply in terms of the Rydberg constant for hydrogen 
 
 
 
 
 R
 
 H
 
 
 
 
 {\displaystyle R_{\text{H}}}
 
 and the <a href="/facts/Rydberg_formula/xKRGYj5V">Rydberg formula</a>.
In <a href="/facts/Atomic_physics/7Jlm4I7k">atomic physics</a>, Rydberg unit of energy, symbol Ry, corresponds to the energy of the photon whose wavenumber is the Rydberg constant, i.e. the ionization energy of the hydrogen atom in a simplified Bohr model.

Rydberg constant open-in-new

Rydberg constant