Will an IR light source "charge" glow-in-the-dark phosphors ? (Tactical science ?)

[hexidismal]

Ok, at first glance S&T seems a weird place for this topic, but I can make a perfectly valid line of reasoning for putting it here at the same time as asking my question.

In discussions with friends and colleagues regarding tactical solutions, one of the topics that I've recently been toying with is the possible applications of 'glow in the dark' items. Just to be clear, I'm referring specifically to the common phospher containing plastics we would generally associate with the term, those which require a 'charge' of light to visibly glow.
I have a whole range of concepts in regards to application, but I'd rather not get into that too deeply and distract from the main point of the thread. It's perhaps only important to understand that I'm thinking in consideration to an urban combat scenario, as opposed to home defense or something like that.

Given such a scenario, and assuming one has a tactical application for a glow in the dark product, then it stands to reason that there would be instances where it would be optimal to expose that product to it's required 'charging' light energy source as covertly and with as little detriment to concealment as possible. Therefore, if it would work, an IR light source should be able to fill that requirement quite admirably. See, this DOES belong in S&T.

So, would it work ? I can't simply do the experiment myself because I don't have an IR light source available to me. If someone knows the science of it right away, or if someone has the light source (IR flashlight/night vision supplement) and is willing to conduct the experiment on a common glow in the dark object, that would be great.

Google searches didn't get me an answer, at least under the search terms I could think of. One thing I did find though is that there are different phosphers which make for active glow in the dark items, and they can vary in what energy/light source is required to sufficiently energize them.

So, will IR light 'charge' commonly glow in the dark items ? If it does not, are there less common known phosphers availible for use in manufacturing that IR light will charge to a visible glow ?

 

[Perfesser]

Generally speaking, 'glow-in-the-dark' paints, plastics, etc, are charged by the ultraviolet component of visible light, rather than the infrared (opposite ends of the spectrum!) Radio Shack used to have both types of LED's and all it takes is an LED, a 9v battery, and a 100 ohm resistor to make an 'invisible flashlight' to see which works.
Check out this site for lots of IR/UV stuff:
www.sciplus.com
This one too:
www.mpja.com

 

[musick]

UV LEDs WILL charge Meprolite sights for sure.

Here is a link to prewired UV LEDs. The site also sells just the LEDs and resistors if you are handy with very basic electronics for much less.

http://www.oznium.com/prewired-leds

You could simply solder a 9-volt snap attachment to the + and - ends. Or you could solder the ends to a wall wort so you wouldnt have to be concerned with the battery going dead, even though LEDs draw very little power.

 

[Jeff White]

No you need visible light to charge them. They do make materials that will reflect IR light. The technology is currently in use by the military.

 

[hexidismal]

Thanks for your responses. I learned some interesting things in researching this further.

First and foremost, it is certainly true that an infrared light source will not 'charge' the phosphor pigments.

Ultraviolet light however and visible light in the violet end of the spectrum will accomplish the process to its peak glow faster and more effectually than standard incandescent lights. That's no surprise really.. BUT what I did not personally know is that scientifically speaking IR and light energy in the red end of the spectrum will apparently manipulate the electrons into position to effectively 'discharge' the glow of the phosphor material. Who knew ? Well, somebody did I suppose, but I sure didn't.

One extra interesting fact: When you expose the phospher glow in the dark material to a standard light bulb ( incandescent white light ), that bulb apparently puts out a mostly equal amount of light within the visible spectrum. Green does not effect the phospher, whereas red and blue end of the spectrum in equal measure effectively cancel each other out. So, the only light energy affecting the phospher pigment is still the UV light alone.

 

[hexidismal]

One other thing, I can actually keep this info "tactical" by mentioning something in regard to the tritium based night sights as mentioned by musick in post #3.

Night sites contain phosphors as well, which are mixed with the radioactive element tritium. The radioactivity 'charges' the phosohor material constantly. Given the info above it stands to reason that UV light, as Musick mentioned, could further charge the phospher material beyond the level the radioactive material is already doing. This would of course make them appear brighter. Apparently though, if my newly learned science is correct, exposure to a source IR light such as a nightvision enhancing flashlight would quickly cause the phosphers to to 'discharge' back down to the level at which the tritium would keep it at normally.

 

[Grizfire]

From the University of Victoria Website...

Look on the left side of the diagram and you can see this diagram is on an energy scale, and the light source will excite the electrons to the upper electronic energy level (excited state). The distance between the ground state and the excited state on that energy scale is the amount of energy required to excite the electron and therefore get phosporescence. Different compounds will have differently spaced energy levels, however, IR light has too low of energy to excite the electron to the excited electronic state.

BTW, I think the part of the diagram that says "excited higher energy triplet states" is wrong, it should say, "excited higher energy singlet states" (singlet is what the S stands for in S1, S2, etc. and the electron certainly would not become a triplet until intersystem crossing has occured??

 

[Grizfire]

oops, double tap