What is Fluoresence?

[lost cat]

Those things freak me out. I went to have my nails done once in one of those crazy nail places and was all like where are your goggles if this thing is really UV light !!! :P :P

The general public seems to have absolutely no awareness of what UV light can do.

 

The nail curing devices I've seen while looking into UV light sources have you put your fingers into a box so not much UV leaks out. The light should also only be on just long enough to do the job. Unless someone has their face next to the box staring at the glow I don't think its too bad.

 

The greater concerns are the solvents. Just walking by I have literally gagged on the stench coming out of some of those nail bars! I can't imagine breathing in those fumes day after day is doing the employees any good.

[Andrea B.]

"Should be" and the reality are two different things in nail salons. Best avoided altogether.

[Shane]

I can't remember any other accepted definition for phosphorescence than one involving an intersystem crossing (electron spin flip). Looking at Wikipedia however it seems that chemiluminescence is incorrectly called phosphorescence (presumably because the timescale is similar).

 

Triplet spin state obviously involves intersystem crossing, it is the decay lifetime associated with the "slow" return that is the issue as the quoted decay times used to "define" phosphorescence vary wildly between the various texts. None of the decay times even come close to what is typically referred to as "phosphorescence", particularly in the geological/mineralogical/gemological community.

 

https://en.wikipedia...iboluminescence

 

I suspect this is the source of light from radium based paint - alpha particles from decaying radium impacting a zinc sulfide phosphor crystal inducing an intersystem transfer which itself decays to emit light.

 

Surely you are not associating radium decay with triboluminescence!

 

Edit: Sorry I misread this, you were in fact saying that radium based paint was a triboluminescence process.

[lost cat]

Triplet spin state obviously involves intersystem crossing, it is the decay lifetime associated with the "slow" return that is the issue as the quoted decay times used to "define" phosphorescence vary wildly between the various texts. None of the decay times even come close to what is typically referred to as "phosphorescence", particularly in the geological/mineralogical/gemological community.

 

 

Well in my book fluorescence is defined as a light induced singlet-singlet electronic transition with the emission of a photon of different energy and the balance lost to/gained from as thermal energy (Stokes/Anti-Stokes) while phosphorescence is similar but due to an intersystem crossover and return.

[Shane]

Well in my book fluorescence is defined as a light induced singlet-singlet electronic transition with the emission of a photon of different energy and the balance lost to/gained from as thermal energy (Stokes/Anti-Stokes) while phosphorescence is similar but due to an intersystem crossover and return.

 

No problem with that, but the only evidence of that process occurring is the emission of light AND the decay times.

[Andrea B.]

merciful heavens you guys

[lost cat]

No problem with that, but the only evidence of that process occurring is the emission of light AND the decay times.

 

I'm guessing the magnetic component of the spin flip can also be measured with an NMR. Not so with fluorescence.

 

merciful heavens you guys

He started it

[Andrea B.]

May we please stipulate that everyone knows their quantum mechanics and stop trying to top off?

Thank you.

 

This is a UV PHOTOGRAPHY forum. Attempting to stay related to that is always a good thing.

[Andy Perrin]

*crunches popcorn* Just when it was getting good, too!

[Andrea B.]

yeah, really !

But we have to remember that the audience is rather more interested in photography.

All these long lectures recently are wearing me out. :D And not a single photograph!

[Pylon]

The type of fluorescence most often encountered in UV photography is the visible light emission, or luminescence, from an object caused by its absorption of high energy ultraviolet light (shorter wavelengths). The absorbed UV photons excite the object's electrons to a higher quantum state. The electrons immediately relax to a lower quantum state and emit photons of lower energy in the form of visible light (longer wavelengths). This visible fluorescence may be successfully photographed.

Ah, so the wave length /does/ go hand in hand with the energetic state of the photon? Meaning that shorter wavelengths = higher energy, by necessity?

[Andrea B.]

Yes. Shorter wavelengths = higher frequency = more energy.

 

It must be added that it is not a linear process, this matter of getting more energy with shorter wavelengths.

There is the amusingly named "ultraviolet catastrophe" where things go awry, all of which is part of the history of quantum theory. But no need to get back into that.

 

For our photographic purposes, we aim high energy UV at appropriate subjects and get back lower energy visible light.

In case anyone new to UVIVF is reading, not everything fluoresces, of course.

 

And ABSTWYG.

always be sure to wear your -OO-

:P

[Pylon]

ah also found this https://en.wikipedia...i/Photon_energy

 

In case anyone new to UVIVF is reading, not everything fluoresces, of course.

 

Okay, so you are saying that when a UV light source is shined onto a certain material, that it is possible that material would not emit/reflect out any visible light whatsoever. I suppose that must be true, sense the object can reflect out the exact same amount of energy that was shined onto it (invisible uv light), OR lower energy visible light. I'd want to try this in a room made of such material. I was probably thinking that "everything fluoresces" because it seems that everything I shine the light on changes color and is visible (even if it is very very dim, it still counts), but if the object is visible that could simply mean fluoresced visible light is bouncing off from walls and other surfaces then is hitting the object that otherwise would appear to 100% "black" under exclusively UV light, or as if no light was shining on it whatsoever.

[Andy Perrin]

Okay, so you are saying that when a UV light source is shined onto a certain material, that it is possible that material would not emit/reflect out any visible light whatsoever. I suppose that must be true, sense the object can reflect out the exact same amount of energy that was shined onto it (invisible uv light), OR lower energy visible light.

OR it can just absorb the light altogether and warm up. It can also do these all at once, in different proportions.

Examples:

1) UV goes in, visible light leaves and the material warms a bit;

2) UV goes in, all of it is absorbed and the material warms even more than in the last example;

3) UV goes in, some UV is reflected, the remainder goes toward fluorescence, which causes some visible light and some heating;

4) Visible light goes in, some is reflected, the rest is absorbed and the material warms a bit.

etc.

 

I tried to illustrate some possible pathways:

[Andrea B.]

If it appears that "everything you shine the light on changes colour and is visible" it is possible that you have some visible light leakage through your excitation filter on your UV illumination source.

 

Go read about the Shiny Metal Test in the Fluorescence Sticky which detects Visible light leak in UV illumination sources. Stainless steel spoons are one thing that does not visibly fluoresce under UV light.

[Cadmium]

The common UV light sources I have tried emit some visible light. Certainly the MTE torch does some, and the 'black light' I have does.

I think it is to be expected unless the source is filtered.

[lost cat]

The common UV light sources I have tried emit some visible light. Certainly the MTE torch does some, and the 'black light' I have does.

I think it is to be expected unless the source is filtered.

 

Blacklight blue bulbs do have a coating of woods glass over their surface.

[Andrea B.]

Wood's glass typically leaks some violet/blue in the Visible range and also some Infrared.

Some black lights may, of course, have other filtration in addition to a Wood's glass coating.

If your Blacklight Blue appears violet when lit, then..................

 

My two Nichia 365-LED chipped torches both emit some violet so I filter them with a 1.25" BaaderU to cut it down some.