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

Polarisation, applications of polarisation with explanation

applications of polarisation with explanation

Illustrate tangent law in magnetism, Illustrate "Tangent law" in magnetism....

Illustrate "Tangent law" in magnetism. Compare magnetic moment of two bar magnet in a tan A, tan B position by null method or equal distance method.

Explain oblique collision, When two objects collide like there velocities a...

When two objects collide like there velocities are not in the line of action of contact force then the collision is known as oblique collision. We can split also oblique collisi

Dielectric material: glass, O rdinary glass is a good insulator but is too ...

O rdinary glass is a good insulator but is too brittle to be used for anything but scientific instrument part s, accumulator container and for certain other special purposes. It is

Poisson equation, Poisson equation (S.D. Poisson) It is the differentia...

Poisson equation (S.D. Poisson) It is the differential form of Gauss' law, such as, div E = rho,

The acceleration of a falling ball, The acceleration of a falling ball ...

The acceleration of a falling ball The change in speed per second of a moving body is called the acceleration. When it is constant as in the case of a ball falling under the ac

Find charge parity - thermodynamics, Find Cp for any substance in terms of ...

Find Cp for any substance in terms of V, T, P and S. Hint: How is C p related to (∂s/∂T) p ?

Image formation for concave mirrors - case a, Image Formation for Concave M...

Image Formation for Concave Mirrors - Case A To look an object within any type of mirror, a person must sight along a line at the image of the object. Whole persons capable of

Newtons laws of motion, a body of mass M is acted upon by a force F and the...

a body of mass M is acted upon by a force F and the acceleration produced is a.if three forces each equal to F and inclined to each other at 120degrees act on the same body,the acc

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