Sharp series

The sharp series is a series of spectral lines in the atomic emission spectrum caused when electrons descend from higher-energy s orbitals of an atom to the lowest available p orbital.

The spectral lines include some in the visible light, and they extend into the ultraviolet.

The sharp series was important in the development of the understanding of electron shells and subshells in atoms.

The sharp series has given the letter s to the s atomic orbital or subshell.

The series is caused by transitions to the lowest P state from higher energy S orbitals.

The terms can have different designations, mS for single line systems, mσ for doublets and ms for triplets.

[2] Since the P state is not the lowest energy level for the alkali atom (the S is) the sharp series will not show up as absorption in a cool gas, however it shows up as emission lines.

In 1896 Arthur Schuster stated his law: "If we subtract the frequency of the fundamental vibration from the convergence frequency of the principal series, we obtain the convergence frequency of the supplementary series".

[5] But in the next issue of the journal he realised that Rydberg had published the idea a few months earlier.

[6] Rydberg Schuster Law: Using wave numbers, the difference between the sharp and diffuse series limits and principle series limit is the same as the first transition in the principal series.

The sodium diffuse series has wave numbers given by:

when n tends to infinity the diffuse and sharp series end up with the same limit.

[3] At Cambridge University George Liveing and James Dewar set out to systematically measure spectra of elements from groups I, II and III in visible light and ultraviolet that would transmit through air.

They noticed that lines for sodium were alternating sharp and diffuse.

[12] They classified alkali metal spectral lines into sharp and diffuse categories.

In 1890 the lines that also appeared in the absorption spectrum were termed the principal series.

Rydberg continued the use of sharp and diffuse for the other lines,[13] whereas Kayser and Runge preferred to use the term second subordinate series for the sharp series.

[14] In 1896 Edward C. Pickering found a new series of lines in the spectrum of ζ Puppis.

[15][16] Heinrich Kayser, Carl Runge and Johannes Rydberg found mathematical relations between the wave numbers of emission lines of the alkali metals.

[17] Friedrich Hund introduced the s, p, d, f notation for subshells in atoms.