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

# ELECTRONICS, #WHAT IS THE PRINCIPLE OF REGULATOR?

#WHAT IS THE PRINCIPLE OF REGULATOR?

Draw a free-body diagram for the elevator, Erika is on an elevator and pre...

Erika is on an elevator and presses the button to go down. When the elevator first begins moving, it has an acceleration of 2.5 m/s 2 downward. Erika and the elevator have

Units and dimensions, what is the dimension and unit of bulk modulus,stress...

what is the dimension and unit of bulk modulus,stress,strain and moment of interia

Working of single –phase induction motor, Working of Single –phase inductio...

Working of Single –phase induction motor Working : Construction of a single -phase motor is same to that of a three -phase induction motor except that the stator is given wit

What is a mole? , It is the molecular weight of a substance expressed in gr...

It is the molecular weight of a substance expressed in grams ; the basic unit of amount of substance adopted under the Systeme International d''Unites.

Homework help, Describe an actual situation that would give rise to the fre...

Describe an actual situation that would give rise to the free body diagram

How is quantum theory conceptual view explained, How is quantum theory conc...

How is quantum theory conceptual view explained? Quantum theory gives us with the rules and regulations of the small world. The quantum theory conceptual foundation is mysterio

What are the magnitude and the direction of rider velocity, A park ride is ...

A park ride is designed so that the rider is on the edge of a revolving platform, 3.5 m from the platform's center. This platform is mounted 8.0 m from the center of a larger revol

Explain the reason when chemical changes, Chemical changes during: Dis...

Chemical changes during: Discharging: The current will flow from positive to negative plate in the external circuit. As current now enters by negative plate, the negative

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