Notes on Hydrogen fine structures
                     Notes on Hydrogen fine
 structure
By
Jayam chemistry 
learners
What is the fine structure of a 
•hTyhed sprliotting oef thne m aint sopecmtral l?ine into 
two or more components with a slight 
variation in wavelength in the magnetic 
field is called fine structure in spectroscopy. 
• These are known as fine structures of the 
main spectral line. The hydrogen spectrum 
exhibiting the fine structured lines is known 
as the hydrogen fine spectrum.
• Hydrogen is the lightest element with a single 
electron in the periodic table. The hydrogen 
atom absorbing external energy shows the 
excitation of its electron. The transition of 
electrons between the two discrete stationary 
energy levels results in the emission of photons 
of definite wavelengths. It shows spectral lines 
in the hydrogen spectrum. 
• Unlike ordinary spectrometers, a high-
resolution spectrometer epitomizes the main 
spectral line splitting into its constituents with a 
slight variation in their wavelengths. The 
splitting of spectral emission lines of the 
hydrogen are known as the hydrogen fine 
structures.
• The cleavage of the main spectral line of the hydrogen 
atom is due to the influence of spin-orbit coupling. 
• The hydrogen fine structure is the splitting of spectral 
lines of the hydrogen atom due to the interaction of 
electron spin with the magnetic field generated by the 
electron revolution around the atomic nucleus. 
• Hence, the interaction of spin electron magnetic moment 
with the magnetic field of electron’s relative motion 
gives the hydrogen fine structures.
• In 1916, Arnold 
Sommerfeld explained the 
splitting of hydrogen 
spectral lines with elliptical 
stationary orbits. 
• And he introduced a 
dimensionless constant α to 
account for the energy 
difference between the gross 
and fine structure 
predictions.
Spin-orbit coupling
The coupling of the magnetic field 
generated by the orbiting electron around 
the nucleus with quantum mechanical spin 
produces fine structures of the hydrogen 
spectrum. So, the hydrogen fine structures 
occur due to the coupling of spin and 
orbital angular momenta. 
Hence, the spin-orbit coupling is a piece of evidence for the splitting of the main spectral 
line into two or more ancillary lines.
• The alkali metal atoms with 1S-electron in their valence shell give spectral line 
doublet in the presence of the magnetic field. 
• But, the alkaline earth metals with two 1S-electrons in their valence shell give 
spectral line triplet due to spin-orbit interaction. 
• In other words, the number of fine structures increases with an increase in the stable 
state configurations in the atom. 
• For this reason, Lithium with atomic number three (i.e., n=3) may not be resolved 
by the average spectroscope. Whereas the Rubidium with atomic number 37 has 
widely separated spectral emissions and can be observed with a normal 
spectroscope.
For more information on this topic, kindly visit our blog 
article at;
https://jayamchemistrylearners.blogspot.com/2022/04/fi
ne-structure-of-hydrogen-atom.html
Our blog discusses interesting topics of chemistry with 
regular new post updates. You can have a look at it and 
follow it.  https://jayamchemistrylearners.blogspot.com/
You can send your valuable suggestions and any doubts 
regarding chemistry subject through these social media 
channels.
Instagram :   
https://www.instagram.com/chemistrylearners/
Pinterest :     
https://in.pinterest.com/kameswariservices/_created/
Facebook     
https://www.facebook.com/jayamchemistrylearners