The Pickering series (also known as the Pickering–Fowler series) consists of three
lines
Line most often refers to:
* Line (geometry), object with zero thickness and curvature that stretches to infinity
* Telephone line, a single-user circuit on a telephone communication system
Line, lines, The Line, or LINE may also refer to:
Arts ...
of singly
ionized
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
helium
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. ...
found, usually in absorption, in the spectra of hot stars like
Wolf–Rayet star
Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface ...
s. The name comes from
Edward Charles 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 Carl Vogel, Pickering discovered the first spectroscopic binary stars. He wrote ' ...
and
Alfred Fowler
Alfred Fowler, CBE FRS (22 March 1868, in Yorkshire – 24 June 1940) was an English astronomer.
Early life and career
He was born in Wilsden on the outskirts of Bradford, Yorkshire and educated at London's Normal School of Science, w ...
. The lines are produced by transitions from a higher energy level of an electron to a level with
principal quantum number
In quantum mechanics, the principal quantum number (symbolized ''n'') is one of four quantum numbers assigned to each electron in an atom to describe that electron's state. Its values are natural numbers (from 1) making it a discrete variable.
A ...
''n'' = 4. The lines have wavelengths:
*4339
Å (''n'' = 10 to ''n'' = 4)
*4541 Å (''n'' = 9 to ''n'' = 4)
*4859 Å (''n'' = 8 to ''n'' = 4)
*5412 Å (''n'' = 7 to ''n'' = 4)
*6560 Å (''n'' = 6 to ''n'' = 4)
*10124 Å (''n'' = 5 to ''n'' = 4)
The transitions from the even-n states overlap with
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
lines and are therefore masked in typical absorption stellar spectra. However, they are seen in emission in the spectra of Wolf-Rayet stars, as these stars have little or no hydrogen.
In 1896, Pickering published observations of previously unknown lines in the spectra of the star
Zeta Puppis
Zeta Puppis (ζ Puppis, abbreviated Zeta Pup, ζ Pup), formally named Naos , is a star in the constellation of Puppis.
The spectral type, spectral class of O4 means this is one of the hottest, and most luminous, stars ...
. Pickering attributed the observation to a new form of hydrogen with
half-integer transition levels. Fowler managed to produce similar lines from a hydrogen–helium mixture in 1912, and supported Pickering's conclusion as to their origin.
Niels Bohr
Niels Henrik David Bohr (; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922 ...
, however, included an analysis of the series in his 'trilogy'
on
atomic structure
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, and ...
and concluded that Pickering and Fowler were wrong and that the spectral lines arise instead from ionised
helium
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. ...
, He
+. Fowler was initially skeptical but was ultimately convinced that Bohr was correct,
and by 1915 "spectroscopists had transferred
he Pickering seriesdefinitively
rom hydrogento helium."
Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory.
[{{cite journal, title = The Spectrum of ζ Puppis and the Historical Evolution of Empirical Data, first = Nadia, last = Robotti, journal = ]Historical Studies in the Physical Sciences
''Historical Studies in the Natural Sciences'' is a peer-reviewed academic journal published by the University of California Press on behalf of the Office for History of Science and Technology (University of California, Berkeley). It was establish ...
, volume = 14, issue = 1, year = 1983, pages = 123–145, doi = 10.2307/27757527, jstor = 27757527
See also
*
Hydrogen spectral series
The emission spectrum of atomic hydrogen has been divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two energy levels in an ...
References
External links
PROTO-HYDROGEN
Astronomical spectroscopy
Helium