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

Magnet, i need to demonstrate the magnetic properties as a part of my assig...

i need to demonstrate the magnetic properties as a part of my assignment. then how can i do that?

Is the common end is important, Is the common end is important? Even th...

Is the common end is important? Even though manufacturers place extra attention on fibers and illuminators the common end is a very important piece for the correct operation of

Why subsequently is there a attractive force on the paper, Question: If...

Question: If you chafe a rubber rod with rabbit fur thus giving the rod a negative charge and bring the rod near a few bits of neutral paper the rod will attract the bits of pa

What is the index of refraction, A 95.7-nm film of an unknown substance is ...

A 95.7-nm film of an unknown substance is able to prevent 555-nm light from being reflected when surrounded by air. What is the index of refraction of the substance   2d

Sketch the x-y intensity pattern, Consider the 4-f system below where an ob...

Consider the 4-f system below where an object is placed at the input plane and is illuminated by a plane wave   The object to the right is placed in the input plane where b

Determine the inside plate temperature, A carbon steel plate (thermal condu...

A carbon steel plate (thermal conductivity = 45 W/m o C) (600 x 900 x 25) mm 2 is maintained at 310 o C. Air at 15 o C bellows over the hot plate. If convection heat transfer co-e

Compute the quantity of sugar contained in the solution, Q A 300 mm long tu...

Q A 300 mm long tube containing 60 cc of sugar solution produces a rotation of 90 when placed in a polarimeter If the specific rotation is 600, Compute the quantity of sugar contai

What is the luminous flux of a flashlight, What is the luminous flux of a f...

What is the luminous flux of a flashlight that provides an luminance of 145 lx to the surface of water when held 0.50 m above the water?

Explain voltmeter, Voltmeter: An electromechanical instrument which is ...

Voltmeter: An electromechanical instrument which is used to calculate potential difference among two points is known as voltmeter. Voltmeter is a modified form of a galvanom

Radioactivity, law of successive diintegration

law of successive diintegration

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