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

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.

#title. entopy., what is entropy and how is it useful in our everyday life?...

what is entropy and how is it useful in our everyday life?

Vectors, example problms of vectors?

example problms of vectors?

Batteries used in the torch lights, Can the batteries used in the torch lig...

Can the batteries used in the torch lights be recharged after their discharge? Give reason? Ans) No,because the NH4Cl corrods the zn containger gradually.so with out anode redox

Relation between a proton and an alpha particle, A proton and an alpha part...

A proton and an alpha particle pass by the gap of a strong magnet.  If both particles have the similar initial velocity, how many times greater will the defection of the proto

Define electric charge, Charge is the characteristic associated with matter...

Charge is the characteristic associated with matter due to which it produces and experiences electrical and magnetic effects.

Semiconductor materials: indium antimonide, Melting point: 525 0 C. It ...

Melting point: 525 0 C. It has small band gap and very high mobility around 70,000Cm 2 /V-Sec. It has much easier to prepare in single crystal from the Gallium arsenide. It is

Power, Power: The rate of doing work is called power, and it is defined...

Power: The rate of doing work is called power, and it is defined as the work done in unit time.  As a formula, this would be: power = work done/time Taken  Power is exp

Define the electromagnetic radiation, Diffraction is a phenomenon that is s...

Diffraction is a phenomenon that is severely associated with light. That is to utter that light and only light undergoes diffraction. (By light here we denote any form of electroma

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