It is the first spectral line of the hydrogen spectrum. The valence electron of the neutral hydrogen gas atom, while moving from the lowest stationary orbit with principal quantum number value n=1 to its immediate next energy level on absorbing energy, gives this Lyman-alpha spectral line in the ultraviolet region of the electromagnetic spectrum. For more information on this concept, please have a look at our blog article; https://jayamchemistrylearners.blogspot.com/2022/05/lyman-alpha-line-chemistry-learners.html

1. The
Lyman-
alpha
line
By
Jayam chemistry learners
Blog URL:
https://jayamchemistrylearners.blo
gspot.com/

2. Introduction:
 The Lyman-alpha spectral line results due to electron transition from the first stationary
ground level of the atom to its immediate next higher orbicular configuration n=2 in
the hydrogen spectrum.
 It was named after the Harvard physicist Theodore Lyman. The Greek letter α denotes
it, and its symbolization is Ly-α.
 The Lyman-alpha spectral line occurs at the longest wavelength of 121.5 nm. And it
has the smallest frequency of 2.47X1015 Hz.
 It lies in the vacuum-ultraviolet region.
 It lies in the vacuum-ultraviolet region. It is characterized by a strong absorption in the
air. Hence, satellite-borne instruments are used to study the Lyman-alpha astronomy.

3. Lyman series electron transition
 The initial principal quantum number
n1value for the Lyman series is 1. And the
final quantum number n2 shows a wide
range variation in values from 2 to ∞ that
results in a bunch of spectral lines in the
Lyman series.
 Comparatively, the discontinuous spectral
appearances confirm the existence of
quantized electron orbits that accounts for
atomic stability.

4. Greek-notation for Lyman series lines
The electron oscillation between n=2 to n=1 gives the Lyman-alpha emission, and
the electron transference from n=3 to n=1 shows the Lyman-beta line. In the same
way, the Lyman-gamma line occurs during the electron transference between n=4
to n=1. The below table shows the Greek-notation of Lyman-alpha transitions that
occur in the hydrogen atom.
n1 value n2 value Greek-letter
notation
Symbolization
n1= 1 n2 =2 Lyman-alpha Ly-α
n1= 1 n2 =3 Lyman-beta Ly-β
n1= 1 n2 =4 Lyman-gamma Ly-γ

5. Scientist life history
 The U.S. Physicist and spectroscopist Theodore Lyman IV was born on
November 23, 1874, in Massachusetts, Boston.
 He completed his Ph.D. from Harvard University in physics and rendered his
service as a Physics professor at Harvard University.
 He researched light radiations of shorter wavelengths, particularly ultraviolet
radiations and their properties. It made him discover the first line in the
ultraviolet region of the Lyman series in 1906.
 By extending his hydrogen spectrum studies, he found the rest of the lines in
the Lyman series from 1906 to 1914.

6. 10.2 eV
n=1
n=2
Energy calculation for Lyman-alpha line
The hydrogen electron has -13.6 eV energy in the first
stationary orbit. When it is in the second orbit, its energy
is -3.4 eV. So, the difference in energy between the first
and second static levels of the hydrogen atom is 10.2 eV.
Therefore, the Lyman-alpha transition requires 10.2 eV
energy to occur.
ΔE= energy difference between the two electron transition states
E1 = Energy of the first main level
E2 = Energy of the second main level

7. Wavelength calculation for Lyman-alpha line
It is the lowest energetic transition of the Lyman
series due to the small energy gap between the
first and second orbicular configurations. Hence,
the Lyman-alpha spectral line occurs at the
longest wavelength of 121.5 nm. The Rydberg
formula is used to calculate the wavelength of the
Lyman-alpha spectral line. The Lyman-alpha
transition has two specificities. One is that it
occurs at the lowest energy than the other electron
transition of the Lyman series. And the second is
that it occurs at the longest wavelength than the
remaining spectral lines of the Lyman series.

8. Frequency calculation for Lyman-alpha line
Similarly, the frequency of the Lyman-alpha spectral line is calculated from the
following equation.
Where,
ϒ = frequency of the light radiation
c = velocity of light in vacuum
λ = wavelength of the light
Where,
c = 3X108 m/sec
λ = 121.5 X10-9 m

9. Lyman-alpha: The most intense spectral line
The hydrogen spectrum reveals that it is the most intense spectral emission line in its
ultraviolet region. This states it is the most abundant hydrogen spectral line in the Lyman
series.
At suitable temperature conditions, the number of hydrogen atoms participating in the
Lyman-alpha transition is more.
And it enhances the photon emissions that influence the intensity of the Lyman-alpha
spectral line.
But, an important thing to remember here is that the intensity of the spectral line does
not impact the number of Lyman-alpha spectral lines appearing in the hydrogen
spectrum since its transition states remain unchanged. Hence, we observe a thick single
Lyman-alpha line at the extreme right end of the hydrogen spectrum.

10. Lyman-alpha: Ozone formation
 Lyman-alpha line helps in Ozone formation.
 In the upper earth's atmosphere, the oxygen
molecules absorb Lyman-alpha emissions of
sunrays. And it dissociates the oxygen
molecules into their atoms.
 Later, the oxygen atoms combine with the
undissociated oxygen molecules to form an
Ozone.
 In this way, Lyman-alpha emissions help save
the earth from harmful radiations by
involving in the Ozone formation.
Ozone formation
Step-1: Dissociation of Oxygen
molecule in to its atoms
Step-2: Recombination of oxygen
atom with oxygen molecule to form
Ozone

11. Lyman-alpha observations from earth
Lyman-alpha observations
 Strong absorption by the air is the characteristic
property of the Lyman-alpha spectral line.
 So, vacuumed spectroscopic equipment is essential
in laboratory for Lyman-alpha observations.
 For this reason, the Lyman-alpha involved
experiments done in satellite-borne instruments,
except when observing the extremely distant
sources whose redshifts allow the Lyman-alpha
line penetrations into the earth's atmosphere.
 Therefore, the Lyman-alpha radiations can redshift
from faraway celestial objects on to earth's crust.

12. Lyman-alpha fine structures
 The Lyman-alpha spectral line splits to give a pair of
spectral lines with a slight variation in their
wavelengths due to the spin-orbit interaction.
Consequently, the Lyman-alpha doublet consists of
closely spaced two spectral emission lines at
wavelengths of about 121.5668 nm and 121.5674
nm. And they are symbolized as Ly-α3/2 and Ly-
α1/2 having j values 3/2 and 1/2, where j is the total
angular momentum of the electron.
 It realizes Ly-α3/2 is high energy transition than Ly-
α1/2. Hence, Ly-α3/2 spectral emission occurs at a
slightly shorter wavelength than Ly-α1/2.

13. Importance of Lyman-alpha in cosmology:
 The quasars serve as high energetic photon
emitters source.
 The light radiations emitted from quasars travel
through the neutral gaseous clouds. The
hydrogen atoms of gas clouds absorb photons
having wavelengths matching the Lyman-alpha
line.
 Hence, the spectra of quasars or distant
galaxies show the Lyman-alpha absorption
line.

14.  The photon absorbed by the hydrogen atom induces the electron transition between the
first and second stationary orbits. And the unstable excited hydrogen electron then
returns to its original position with the emission of light radiation at 121.5 nm. It shows
the Lyman-alpha spectral emission line in the spectrum.
 Both absorption and emission of quasar photons occur concurrently in the universe due
to the abundance of neutral hydrogen gas clouds and the quasars.
 So, the Lyman-alpha spectral studies help identify the presence of neutral hydrogen
atoms in the universe. And it contributes to understanding the properties of celestial
matter and its distribution, like hot dark matter.
 It helps to calculate the cosmological constant by comparing the angular and radial
lengths of the astronomical object at its redshift.

15. https://jayamchemistrylearners.blogspot.com/2022/05/lyman-alpha-line-chemistry-learners.html
For more information on this concept, kindly visit our blog article at;
https://jayamchemistrylearners.blogspot.com/2022/05/lyman-alpha-line-chemistry-
learners.html
For more interesting concepts of chemistry, kindly follow us at;
Instagram- https://www.instagram.com/chemistrylearners/
Pinterest- https://in.pinterest.com/kameswariservices/_created/
Quora space- https://kameswariconsultancyservicessspace.quora.com/