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

What is the boat speed relative to the dock, A river is flowing 4.0 m/s to ...

A river is flowing 4.0 m/s to the east. A boater on the south shore plans to reach a dock on the north shore 30.0° downriver by heading directly across the river. a. What shoul

Work and energy, calculate the work required to be done to stop a car of 15...

calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?

What instrument is used to measure volume, What instrument is used to measu...

What instrument is used to measure volume? Liquid volume is calculated with beakers, measuring cups, spoons, graduated cylinders, and the like. For regular objects, solid volum

The force exerted on second charge, a)  A charge of 3X10 -4 Coulomb at P (...

a)  A charge of 3X10 -4 Coulomb at P (1, 2, 3) and a charge of -10 -4 Coulomb at N (2, 0, 5) in a vacuum. We desire to measure the force exerted on second charge beacuse of  firs

Kinametic, whatis meant by kinametic?

whatis meant by kinametic?

Explain tangent law , When a small size magnet is laid in two uniform magne...

When a small size magnet is laid in two uniform magnetic fields and which are at right angles to each other, the magnet comes to rest at an angle Φ with respect to B h   like that

Motion in one dimension, a ball is dropped from a bridge 122.5m high. afte...

a ball is dropped from a bridge 122.5m high. after the ball has been falling for2 sec another is thrown straight downwards after it. the initial velocity of the ball is such that

Define electric potential, Define: Electric potential. The electric po...

Define: Electric potential. The electric potential in an electric field at a point is define as the amount of work done in moving a unit positive charge from infinity to that

How many arsenic atoms should there be for each silicon atom, Silicon has 1...

Silicon has 1.45 x 10 10 free electrons/cm 3 at room temperature. If you wanted to have 3x10 6 as many electrons from arsenic doping as thermal free electrons from silicon at ro

Vector and scalar, why are vector and scalar necessary in our everyday acti...

why are vector and scalar necessary in our everyday activities?

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