MadSci Network: Physics

Re: Why does a he-ne laser 'deactivate' glow-in-the-dark?

Date: Thu Jan 27 12:06:51 2000
Posted By: Matthew B. Weyerich, Technical Coordinator,ES&R Dept., CPI Corp.
Area of science: Physics
ID: 947709472.Ph

Greetings, Herb!

Well, you've certainly piqued my curiosity with this question!

I believe what you are referring to is a change in the energy state of the 
electrons of your glow-in-the-dark material. You're looking at quantum 
mechanics in action!

Glow-in-the-dark materials exhibit phosphorescence and florescence because 
their electrons become "excited" above their "ground" (lowest, 
"non-glowing") energy state, then give off light / heat as they return. The 
electrons in phosphorescent materials remain in a higher-energy 
"metastable" state for a time after excitation, slowly giving off their 
energy as the glow we see. ("Glow-in-the-dark" materials often mix 
florescent chemicals with phosphorescent chemicals to enhance brightness, 
color, etc.) 

Your laser probably doesn't have the power / frequency to excite the 
electrons from the ground state, but it's probably perfect for pushing 
metastable electrons "over the top" so they fall back down to their ground 
state. (Unless you have a REALLY powerful laser, in which case, you might 
be burning your target!) 

The following links will explain in a little more detail. If this doesn't 
describe what you've observed, or, if you have further questions, feel free 
to e-mail me at . It sounds as if you've found something 
interesting I'd like to learn more about!

Your MadSci,

General Concept:

MadSci Archive answer: /cgi-bin/circR?/

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