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

Situation of the converging lens - principle ray 1, Q. Situation of the con...

Q. Situation of the converging lens - Principle Ray 1? Principle Ray I . The easy one just as in the case of the converging lens this ray goes straight through the centre of t

What is the universal law of universal gravitation, What is the universal l...

What is the universal law of universal gravitation? Statement that any particle of matter in the universe attracts any other with a force varying directly as the product of the

Inertia with a spade, Inertia with a spade Scoop up a spadeful of dry e...

Inertia with a spade Scoop up a spadeful of dry earth. Now pitch the earth away from you. View that when the spade stops the earth flies on due to inertia.

Determine the pressure - hydraulics and hydrology, Points A and B are separ...

Points A and B are separated by 3000 ft of new 6-in schedule-40 steel pipe. 800 gpm of 60 deg F of water flow from point A to point B. Point B is 60 ft above point A. What must be

What is a wave motion, Wave motion is the motion in which the particle/matt...

Wave motion is the motion in which the particle/matter remains at the point where it is.  But the disturbance/energy gets transfer from one point to the other.  The particle just o

Explain one ohm, 1 OHM: If a potential difference of 1 volt is applied ...

1 OHM: If a potential difference of 1 volt is applied across the ends of a conductor and the resulting current flowing by the conductor is 1 ampere, the resistance of the condu

State brewsters law, Q. State Brewster's law. Brewster's law the digres...

Q. State Brewster's law. Brewster's law the digression of the polarising angle is numerically equal to the refractive index of the medium. That is tan ip = μ

Kinematics, A body moving in the positive x direction passes the origin at ...

A body moving in the positive x direction passes the origin at time t=0. Between t=0 and t=1 second, the body has a constant speed of 24 meters per second. At t=1 second, the body

Theory of searles magnetometer, theory of searles magnetometer for do the e...

theory of searles magnetometer for do the experiments

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