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

PVD, In order to deposit films of the alloy YBa2Cu3, the metals Y, Ba, and ...

In order to deposit films of the alloy YBa2Cu3, the metals Y, Ba, and Cu are evaporated from three point sources. The latter are situated at the corners of an equilateral triangle

Find the power rating of the heater, Electrical equipment in an office take...

Electrical equipment in an office takes a current of 13A from a 240V supply. Estimate the cost per week of electricity if the equipment is used for 30 hours every week and 1kW

Explain phenomenon of scattering, Some phenomenon based on scattering: (...

Some phenomenon based on scattering: (i) Sky looks blue because of scattering. (ii)  At the starting time of sunrise or sunset sun looks reddish. (iii) Danger signals are

Motion animation, Motion Animation A car along with a non-zero initial ...

Motion Animation A car along with a non-zero initial speed has a constant acceleration whose value could be controlled through the user.

Explain resistance, Resistance: Resistance is the opposition to the mot...

Resistance: Resistance is the opposition to the motion of electrons. This arises as a result of collision of moving electrons. The unit of resistance is "ohm" represented by

Describe critical angle, With a neat and clean diagram illustrate in brief ...

With a neat and clean diagram illustrate in brief the TIR. Describe critical angle and mention the two conditions for TIR.

Drake equation, Drake equation (F. Drake; 1961) A technique of estimat...

Drake equation (F. Drake; 1961) A technique of estimating the number of intelligent, technological species (that means, able to communicate along with other species) in existe

P2 work, what is the tension in the string when the block is lifted at a st...

what is the tension in the string when the block is lifted at a steady speed when the weight weighs 4.5N and the distance is 90cm

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

Mass transfer operation - distillation column design , A mixture of methano...

A mixture of methanol and water is to be separated in a new separation unit and you are required to provide a report detailing the design and costing of a distillation column with

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