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

Define the brightness mode of display in brief, Define the brightness mode ...

Define the brightness mode of display in brief. B-Mode Into the B-mode or Brightness mode of display, the time-of-flight (i.e., travel time) of the sound energy is exhibited

Define angle of repose, Define angle of repose Consider a body resting ...

Define angle of repose Consider a body resting on a plane OA. Assume this plane OA is slowly raised from the horizontal position to incline it with the horizontal.

Physical interpretation of wave function, Physical interpretation of wave f...

Physical interpretation of wave function : Einstein proposed a historic relationship between energy and mass using postulates of STR. The variation of mass with velocity has modif

Fringes, What is the definition of fringes

What is the definition of fringes

Temperature co-efficient of resistance, The temperature co-efficient of res...

The temperature co-efficient of resistance: The temperature co-efficient of resistance is defined as;           The Fractional change in resistance from 0ºC, per degree temp

Time of flight, projectile down an inclined plane

projectile down an inclined plane

Pie, my question is regarding value of pie whether its decimal value which ...

my question is regarding value of pie whether its decimal value which has non-repeating nature goes to infinity or it ends at some place?

Explain earth’s magnetic field , As per the most established theory it is b...

As per the most established theory it is because of the rotation of the earth where by the several charged ions there in the molten state in the core of the earth rotate and consti

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