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

What is the frequency of the vibrator, In the arrangement shown in figure, ...

In the arrangement shown in figure, an object can be hung from a string (with linear mass density µ = 0.002 00 kg/m) that passes over a light pulley. The string is connected to a v

Ac current, what is alternating current

what is alternating current

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

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

How to find out percentage error, Take the difference among your experiment...

Take the difference among your experimental value and your known value, and divide that difference by your know value. Say you experimentally found the force of gravity to be 8m/s

Illustrate gibbs - helmoltz equation, Illustrate Gibbs - Helmoltz equation....

Illustrate Gibbs - Helmoltz equation. What are its applications? A Heat engine operating between temperatures 300 K and 500 K rejects 6 Kcal of heat to the sink. How much heat i

Which is equal to a newton, A Newton is equal to which of the following? ...

A Newton is equal to which of the following? a)  kilogram-meter per second b)  meter per second squared c)  Kilogram-meter per second squared d)  Kilogram per

Explain minimum uncertainty in its momentum?, Derive the expression for the...

Derive the expression for the distance between the atomic planes such as (100) and (110) planes of the cubic crystals The position and momentum of a 1 keV electron are simultane

What are their wavelengths, A hydrogen atom is in the ground state. It abso...

A hydrogen atom is in the ground state. It absorbs energy and makes a transition to the  n  = 3excited state. The atom returns to the ground state by emitting two photons. What are

Calculate the capacitance of the capacitor, A parallel plate capacitor has ...

A parallel plate capacitor has nineteen interleaved plates each 75mm by 75mm separated by mica sheets 0.2mm thick. Assuming the relative permittivity of the mica is 5. Calcu

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