Population inversion, Physics

Assignment Help:
population inversion
  • The process in which the number of electrons (N2) in a higher energy state called ‘metastable state of an active medium is increased to a value greater than the number of electrons (N1) in the ground state (i.e.N2 > N1) is called population inversion.
  • There are certain special substances or systems in which the electrons, once excited can remain in the higher energy state for longer times.
  • Such systems are called Active systems or Active Media.
  • Active systems are generally compounds or mixtures of different elements.
  • Consider three electronic states 1,2,3, in an active medium. (Refer text book for diagram.
  • Normally Large number of electrons exist in the Lowest energy state called ground state.
  • Let this number be N1 when photons of energy equal to the difference between E3 and E1 are incident, the electrons from state (1) are excited to state (3) because of absorption. But the property of the state (3) is such that the life time of electrons
  • in the state is very short, of the order 10-8 seconds. 
  • Of course most electrons return to state (1) from state (3) by spontaneous emission, but some electrons go to state (2) also.
  • Therefore, the electrons from the state (3) undergo a quick transition to the state (2) by emitting only a small energy (E3 - E2) which is simply absorbed as the thermal energy by the medium itself.

Related Discussions:- Population inversion

The time base control 3, The Time Base Control 3 Shows the effect of ch...

The Time Base Control 3 Shows the effect of changing the time base control on the display when there is an input voltage varying in time when the frequency of the voltage is hi

Write an equation expressing interest rate, Q. Assume an economy is in a li...

Q. Assume an economy is in a liquidity trap. A. Write an equation expressing interest rate parity under a fixed exchange rate regime. Answer: Liquidity trap entail R = 0

Why is heavy water used as a moderator, Why is heavy water used as a modera...

Why is heavy water used as a moderator? Heavy water is a type of water highly enriched in the hydrogen isotope deuterium. We can conclude the neutron interactions with billiard

Young''s double slits experiment, describe young''s double slits experiment...

describe young''s double slits experiments for interference of light ?

Illustrates some way to by which ultrasonic waves propagated, Illustrates s...

Illustrates some way to by which ultrasonic waves propagated? Detection of Ultrasonic Waves: Ultrasonic waves propagated by a medium can be detected within a number of ways.

Executing simple harmonic motion, The total energy of a particle, executing...

The total energy of a particle, executing simple harmonic motion is Ans) In simple harmonic motion when  a particle is displaced to a position from its mean position, then its kin

Kohlrauschs law, Kohlrausch's law (F. Kohlrausch): If a salt is dissol...

Kohlrausch's law (F. Kohlrausch): If a salt is dissolved into water, the conductivity of the solution is the total of two values one based on the positive ions & the other dep

Are end fitting standard, Are end fitting standard? No, end fitting are...

Are end fitting standard? No, end fitting are not standard. Each system manufacturer favors a type of termination for his fibers along with threads, pressure glands, rivets or

What is the hardness of water, What is the hardness of water? How is it exp...

What is the hardness of water? How is it expressed? Hardness is the property of water which stops lather formation with soap. This is because of the presence of certain salts o

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd