Notes on Hydrogen fine structures.pdf

The splitting of the main spectral line into two or more components with a slight variation in wavelength in the magnetic field is called fine structure in spectroscopy. It means that, in the magnetic field, the electron energy splits to give its sub-states. The electron transitions from these substituent energy levels give additional spectral lines. 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.

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1. Notes on Hydrogen fine
structure
By
Jayam chemistry learners

2. •The splitting of the main spectral line 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.
What is the fine structure of a hydrogen atom?

3. •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.

4. •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.

5. •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.

6. Spin-orbit coupling
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 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.

7. •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.

8. For more information on this topic, kindly visit our blog article at;
https://jayamchemistrylearners.blogspot.com/2022/04/fine-structure-of-hydrogen-
atom.html
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