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

Plane and the package, Plane and The Package Suppose a plane moving alo...

Plane and The Package Suppose a plane moving along with a constant speed at an elevated height above the Earth's surface. Within the course of its flight, the plane drops a pac

Can two candles be taken as coherent sources, Can two candles be taken as c...

Can two candles be taken as coherent sources? Explain how.

Discuss short note on galvanometer, It is an instrument used to detect smal...

It is an instrument used to detect small current passing by it by showing deflection. Galvanometers are of dissimilar types e.g. moving coil galvanometer, moving magnet galvanomete

Benefits of fiber-optic sensors for harsh environments, What are benefits o...

What are benefits of fiber-optic sensors for harsh environments? Benefits of fiber-optic sensors for harsh environments are illustrates below: a. Small, contact measurements

Define surface contaminations (wisconsin-madison), Define Surface Contamina...

Define Surface Contaminations (Wisconsin-Madison)? A surface scientist wishes to remain an exposed surface "clean" (≤ 0.05 adsorbed monolayer) for an experiment lasting for tim

Explain units and dimensions, Do not confuse units and dimensions. We can u...

Do not confuse units and dimensions. We can use dissimilar units to measure the same physical quantity. So, for example, you can calculate the mass in units of kilograms, poun

Angular speed, A ballerina begins a tour jete with angular speed ?i and a r...

A ballerina begins a tour jete with angular speed ?i and a rotational inertia consisting of two parts: Ileg = 1.55 kg*m^2 for her leg extended outward at angle ? = 90.0 to her body

#Inductance balanced delta connected load, how to you calculate the inducat...

how to you calculate the inducatnce on a balanced delta circuit?

Explain fungal prophylaxis in hsct, Fungal Prophylaxis in HSCT  A prosp...

Fungal Prophylaxis in HSCT  A prospective randomized double- blind trial in 882 adults and children compared prophylaxis with mica fungin 50 mg IV once daily (1 mg/kg for patie

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