How do the Spectral lines of hydrogen and deuterium compare?

The spectral lines of hydrogen and deuterium are very similar, as both elements have a single electron and share the same electronic structure. However, deuterium, being an isotope of hydrogen with an additional neutron, has slightly different energy levels due to its greater mass. This results in the spectral lines of deuterium being shifted to longer wavelengths (redshifted) compared to hydrogen, which can be observed in their respective emission and absorption spectra. The differences, while small, are measurable and can be used in various applications, such as spectroscopy and astrophysics.