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Fluorescence

rocketparrotlet

rocketparrotlet

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What is fluorescence and how is it created? I don't understand how a beam of 405nm light can hit a certain chemical, such as chlorophyll, and send out something like 650nm. Why and how does this occur?

-Mark
 





rocketparrotlet said:
What is fluorescence and how is it created?  I don't understand how a beam of 405nm light can hit a certain chemical, such as chlorophyll, and send out something like 650nm.  Why and how does this occur?  

-Mark
Click to expand...

Short answer (almost no science) is that the ultra-violet light excites the electrons in reactive materials enough to force them to "jump" from one energy level to another. When they slip back into their original energy level, they give off a photon. That photon has nothing to do with the wavelength of the UV light. It has its own wavelength.

Peace,
dave
 
Dead nut on. Fluorescence is simply the release of energy from an atom in response to energy added to the atom. The amount of energy in equals the amount of energy out. The energy out, however, is a longer wavelength (lower energy) photon. The rest of the energy is released as radiative or non-radiative energy. In non-radiative release the energy is transferred to something else, like the walls of the container, as in a fluorescent light or it can be radiative by releasing a photon at each transition back to ground state.

In a YAG laser, the YAG rod actually fluoresces. It absorbs photon radiation at several wavelengths via a lamp or at 808nm if diode pumped and releases that energy at 1064nm as well as some other wavelengths. A few photons of course happen to be released parallel to the cavity and gain begins resulting in a 1064nm laser beam but there is quite a bit of fluorescent light generated that escapes the rod.
 
So that is actually laser fluorescence? :D What about in the case of the N[sub]2[/sub] laser pumped rhodamine laser? is that something similar? :-/
 
Yes, rhodamine dye is a fluorescent organic laser dye.

If the photons do not resonate then they are lost as fluorescence. In the case of rhodamine G6 they can be anywhere from green to red depending on the transition configuration.
 
So in theory, any of these 'fluorescent' materials could become lasers, with the only (very big) problem being that they don't have the correct optical properties to reflect a beam through? For example if a yag rod were actually foggy inside, it wouldn't work as a laser because one couldn't form the cavity to make it work, but it would still have the correct properties. Am I making any sense or does this just sound nuts? ;D ;D
 
daguin said:
[quote author=rocketparrotlet link=1225085725/0#0 date=1225085725]What is fluorescence and how is it created?  I don't understand how a beam of 405nm light can hit a certain chemical, such as chlorophyll, and send out something like 650nm.  Why and how does this occur?  

-Mark
Click to expand...

Short answer (almost no science) is that the ultra-violet light excites the electrons in reactive materials enough to force them to "jump" from one energy level to another.  When they slip back into their original energy level, they give off a photon.  That photon has nothing to do with the wavelength of the UV light.  It has its own wavelength.

Peace,
dave[/quote]

Thanks, I totally understand this. That's actually not that complex! What if an electron were to jump up more than one level? Can this happen?

-Mark
 
Well that's not entirely true. Something can fluoresce and still not be good as a lasing medium. You need to have specific transitions available to the medium to allow an inversion in the upper energy state. If something accepts a photon of some wavelength and instantly or near instantly releases that energy there is no time for stimulated emission to occur.

Look into lasing transitions of three and four level laser systems to understand why and where the inversion occurs.
 
I REMEMBER LEARNING ABOUT THIS IN SCIENCE, ALONG TIME AGO, WHEN WE TALKED ABOUT CHEMICAL REACTIONS AND CONSERVATION OF MASS AND ENERGY
 
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