The sharp series is a series of
spectral line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...
s in the atomic
emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a atomic electron transition, transition from a high energy state to a lower energy st ...
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 lines get closer and closer together as the frequency increases never exceeding the series limit. 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
In atomic theory and quantum mechanics, an atomic orbital is a function describing the location and wave-like behavior of an electron in an atom. This function can be used to calculate the probability of finding any electron of an atom in any spe ...
or subshell.
The sharp series has a limit given by
The series is caused by transitions to the lowest P state from higher energy S orbitals.
One terminology to identify the lines is: 1P-mS
But note that 1P just means the lowest P state in an atom and that the modern designation would start at 2P, and is larger for higher atomic numbered atoms.
The terms can have different designations, mS for single line systems, mσ for doublets and ms for triplets.
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.
The
Rydberg correction The term quantum defect refers to two concepts: energy loss in lasers and energy levels in alkali metal, alkali elements. Both deal with quantum systems where matter interacts with light.
In laser science
In laser science, the term "quantum defect ...
is largest for the S term as the electron penetrates the inner core of electrons more.
The limit for the series corresponds to
electron emission
In physics, electron emission is the ejection of an electron from the surface of matter, or, in beta decay (β− decay), where a beta particle (a fast energetic electron or positron) is emitted from an atomic nucleus transforming the original nu ...
, where the electron has so much energy it escapes the atom.
Even though the series is called sharp, the lines may not be sharp.
In
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
s the P terms are split
and
. This causes the spectral lines to be
doublets, with a constant spacing between the two parts of the double line.
Names
The sharp series used to be called the second subordinate series, with the diffuse series being the first subordinate, both being subordinate to the
principal series
Principal series may refer to:
* Principal series (spectroscopy)
In atomic emission spectroscopy, the principal series is a series of spectral lines caused when electrons move between p orbitals of an atom and the lowest available s orbital. These ...
.
Laws for alkali metals
The sharp series limit is the same as the
diffuse series
The diffuse series is a series of spectral lines in the atomic emission spectrum caused when electrons jump between the lowest p orbital and d orbitals of an atom. The total orbital angular momentum changes between 1 and 2. The spectral lines inclu ...
limit. In the late 1800s these two were termed supplementary series.
In 1896
Arthur Schuster
Sir Franz Arthur Friedrich Schuster (12 September 1851 – 14 October 1934) was a German-born British physicist known for his work in spectroscopy, electrochemistry, optics, X-radiography and the application of harmonic analysis to physics. S ...
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".
But in the next issue of the journal he realised that Rydberg had published the idea a few months earlier.
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.
*This difference is the lowest P level.
Runge's Law: Using wave numbers the difference between the sharp series limit and fundamental series limit is the same as the first transition in the diffuse series.
*This difference is the lowest D level energy.
Sodium
![Energy levels of sodium atom](https://upload.wikimedia.org/wikipedia/commons/4/41/Energy_levels_of_sodium_atom.png)
The sharp series has wave numbers given by:
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.
Potassium
Alkaline earths
A sharp series of triplet lines is designated by series letter ''s'' and formula ''1p-ms''. The sharp series of singlet lines has series letter ''S'' and formula ''1P-mS''.
[
]
Calcium
Calcium has a sharp series of triplets and a sharp series of singlets.
Magnesium
Magnesium has a sharp series of triplets and a sharp series of singlets.[
]
History
At Cambridge University George Liveing and James Dewar
Sir James Dewar (20 September 1842 – 27 March 1923) was a British chemist and physicist. He is best known for his invention of the vacuum flask, which he used in conjunction with research into the liquefaction of gases. He also studied ato ...
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. They were the first to use the term "sharp" for the lines. 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, whereas Kayser and Runge preferred to use the term second subordinate series for the sharp series.
Arno Bergmann found a fourth series in infrared in 1907, and this became known as Bergmann Series or fundamental series.
In 1896 Edward C. Pickering
Edward Charles Pickering (July 19, 1846 – February 3, 1919) was an American astronomer and physicist and the older brother of William Henry Pickering. Along with Hermann Carl Vogel, Carl Vogel, Pickering discovered the first spectroscopic binary ...
found a new series of lines in the spectrum of ζ Puppis
Zeta Puppis (ζ Puppis, abbreviated Zeta Pup, ζ Pup), formally named Naos , is a star in the constellation of Puppis.
The spectral class of O4 means this is one of the hottest, and most luminous, stars visible to the ...
. This was believed to be the sharp series of hydrogen. In 1915 proof was given that it was actually ionised helium - helium II
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. It ...
.
Heinrich Kayser
Heinrich Gustav Johannes Kayser ForMemRS (; 16 March 1853 – 14 October 1940) was a German physicist and spectroscopist.
Biography
Kayser was born at Bingen am Rhein. Kayser's early work was concerned with the characteristics of acoustic waves ...
, Carl Runge
Carl David Tolmé Runge (; 30 August 1856 – 3 January 1927) was a German mathematician, physicist, and spectroscopist.
He was co-developer and co-eponym of the Runge–Kutta method (German pronunciation: ), in the field of what is today known a ...
and Johannes Rydberg
Johannes (Janne) Robert Rydberg (; 8 November 1854 – 28 December 1919) was a Swedish physicist mainly known for devising the Rydberg formula, in 1888, which is used to describe the wavelengths of photons (of visible light and other electrom ...
found mathematical relations between the wave numbers of emission lines of the alkali metals.[
]Friedrich Hund
Friedrich Hermann Hund (4 February 1896 – 31 March 1997) was a German physicist from Karlsruhe known for his work on atoms and molecules.
Scientific career
Hund worked at the Universities of Rostock, Leipzig, Jena, Frankfurt am Main, and Göt ...
introduced the s, p, d, f notation for subshells in atoms. Others followed this use in the 1930s and the terminology has remained to this day.
References
{{Reflist, 30em
Emission spectroscopy
Atomic physics