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

Explain about the transmission electron microscope, Explain about the trans...

Explain about the transmission electron microscope. The Transmission Electron Microscope Transmission electron microscopy (TEM) is a microscopy method; a beam of electrons i

Diffraction, Give the theory of plane diffraction grating for normal incide...

Give the theory of plane diffraction grating for normal incidence.

Define amu and mass defect, Q. Define: 1 amu One atomic mass unit is th...

Q. Define: 1 amu One atomic mass unit is thinks as one twelfth of the mass of carbon atom 6 C 12 . 1 amu = 1.66 X 10 -27 kg. Q. Define: mass defect. The dissimi

Motion, An athlete run a certain distance before taking a long jump. Why?

An athlete run a certain distance before taking a long jump. Why?

The current–voltage characteristic , The current–voltage characteristi...

The current–voltage characteristic curve for a semiconductor diode as a function of temperature T is given by the equation i = i0(eev/kt - 1) Here the ?rst symbol e represen

Single pv cell design., give the complete explaination with design formulae...

give the complete explaination with design formulae of single pv cell?

Measure the percentage change in its resistance, A cylindrical metallic wir...

A cylindrical metallic wire is stretched to enhance its length by 5%. Measure the percentage change in its resistance.

The atomic number of an element represents, The atomic number of an element...

The atomic number of an element represents: (1) Number of neutrons in the nucleus   (2) Number of protons in the nucleus  (3)Atomic weight of element  (4)Valency of el

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