How does an electron decide when to de-excite?

[quawa99]

after an electron is excited to a higher energy orbit ,when exactly does it go back to some of the lower energy orbits?

 

[Rohan1997]

It's spontaneous

 

[quawa99]

do you mean random?

 

[Rohan1997]

do you mean random?

yeah

 

[Drakkith]

It's all based on probability. Each state has a particular probability of transitioning to a lower energy state per unit of time and some states take longer or shorter to transition than others. I wish I had a good link for you, but the ones I can find at the moment are knee-deep in quantum mechanical terms, which are over even my head.

 

[256bits]

Wiki, which is a good place to start, has a text on Spontaneous emission,
http://en.wikipedia.org/wiki/Spontaneous_emission

Note the section on probability in the Introduction and the similarity with radioactive decay.
And the section on Theory and Rate, where, as always, it requires more grey-matter usage.

 

[gleem]

Also see this link to Einsteins development of spontaneous emission coefficents several years before the introduction of QM

http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/eincoef.html

 

[lonely_nucleus]

when electrons are exiced they absorb energy so they jump to a higher orbit(shell), when they go into lower shells they release energy in the form of electromagnetic waves.