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B Red laser erases on glow in the dark surfaces?

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  1. Mar 1, 2017 #1
    Hey guys,

    So recently I came across a weird phenomenon...
    Basically, I shined a red laser on a glow in dark surface and the laser could erase it. The fun fact is that before the laser erases the are, it makes it glow for a short time. You need good goggles to see the glow despite the intense red light.
    I expected that, since you can't just lose that energy.
    Is there any scientific explanation for this erasing?

    Thanks ;)
     
  2. jcsd
  3. Mar 1, 2017 #2

    Drakkith

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    Staff: Mentor

    What do you mean by "erasing"? Is the phosphorescent surface already glowing prior to shining the laser on it?
     
  4. Mar 2, 2017 #3
    The laser makes the surface radiate all the energy, so it doesn't glow anymore
     
  5. Mar 2, 2017 #4
    UPDATE: Every wavelength longer then the emitted wavelength is able to do the trick.
     
  6. Mar 2, 2017 #5

    Drakkith

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    Staff: Mentor

    So the surface is glowing, then you illuminate it with a red laser (which also makes it glow, but in a different way?), and it stops glowing wherever you've illuminated it?
     
  7. Mar 4, 2017 #6
    What was the material that was glowing? Could you tell what colour it glowed when you shone the laser on it? Was the erasure permanent? (What happened the next day?)

    It's possible (though it seems unlikely) that your laser was causing the glowing material to decompose chemically. It also seems possible that the material was glowing as the result of some slow transformations in the material--think of energy trickling down from state to state until it gets emitted as light. Perhaps your laser caused some steps in the process to speed up, so that the lower levels got suddenly emptied, and the glow couldn't return until the they were refilled by the trickles from above.
     
  8. Mar 5, 2017 #7
    -Material: glow in dark surface
    -Color: green
    -yes it was permanent
    -the next day nothing happened since it stayed in the dark and thus wasn't charged by a short wavelength
     
  9. Mar 5, 2017 #8
    By "material" I meant, what were you shining the laser on? Wood, painted metal, stone, cloth? Etc.?

    If you leave the material in its normal state for a day or so, does it start glowing again the way it did at first?
     
  10. Mar 6, 2017 #9
    -Phosphorescent T-shirt
    -again: it stops glowing if it's not recharged through a shorter wavelength than green.
     
  11. Mar 6, 2017 #10
    To answer your original question: Yes I'm pretty sure there is a scientific explanation. But I'm not the best person to give it.

    I think my original guess is reasonable: the tee shirt contains a phosphorescent dye that absorbs short-wavelength light and re-emits it slowly at longer wavelengths. (Phosphorescent is in fact a technical term referring to a type of luminescence that can be very slow.) Somehow the laser short-circuits this emission (I can't be specific about how, but it seems credible) causing all the stored-up energy to be released; and the phosphorescence stops until the dye is "charged up" again by short-wavelenth light.

    Best I can do.
     
  12. Mar 6, 2017 #11

    Drakkith

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    I'm still confused about this:

    Please elaborate on this if you can.
     
  13. Mar 6, 2017 #12
    Phosphorescence requires an instable exited state and a metastable intermediate state below it. The glow is charged by lifting the electrons into the exited state and a following electron transition into the metastable state. The charging frequency must be high enough to reach the exited state and it should not interact with the electrons which are already in the metastable state.

    With the red laser you have the reversed situation. It has the right energy to release the electrons from the metastable state (forcing them to return to the ground state and emit the energy difference as light) but not enough energy to lift them into the exited state to charge the glow again.
     
  14. Mar 6, 2017 #13

    Drakkith

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    Interesting. Do you have any good references where I can read more on this?
     
  15. Mar 7, 2017 #14
    Unfortunately not, but maybe you can find references with the keywords "phosphorescence" for the charging process and normal luminescence as well as "photostimulated luminescence" for the erasing process.
     
  16. Mar 7, 2017 #15
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