Date: Tue, 26 Apr 2005 08:39:15 -0500

Author: "Papp, James J "

Subject: RE: UV Lamp

Post:

Hi all,

I thought it was the energy levels of the outer shell electrons of the atoms / molecules of the material that dominated absorption and transmission. Available electrons at the energy level of the photon results in absorption followed by lots of things like re-emission, fluorescence, phonons, free electrons or holes wandering around, and so on. Some materials have wide energy level bands at which they can soak photons, some have narrow bands. There's more to it, and I would appreciate any feedback or articles people have found useful.

Thanks,

Jim Papp

-----Original Message-----
From: Urs Lauterburg [mailto:urs.lauterburg@phim.unibe.ch]
Sent: Saturday, April 23, 2005 1:34 PM
To: tap-l@listproc.appstate.edu
Subject: Re: UV Lamp


Stan Dodds wrote among other things:
>....glass is
>opaque, but quartz is transparent at this wavelength. You want a lamp
>labeled "short wave" or "germicidal", which indicates a quartz bulb and
>copious 254 nm emission. H&R seems to carry these, but you might also
>find them locally at a specialty lamp distributor or janitorial supply
>house. With luck, you might even find one that fits your H&R fixture.

I have always wondered about the exact physical mechanism responsible for
UV passing through Quarz glass. If somebody understands it precisely I
would be glad to get an explanation or a pointer to an article or so. It
must have something to do with the quantum mechanical interaction of light
with the different macroscopic structures of glass versus quarz. What ist
the difference? Aren't booth amorphous?

Anyway, glass cuts off electromagnetic waves above 600nm wavelengths
whereas quartz is still opaque for ''long'' wave UV. I don't even know at
what wavelengths quarz will block too.

Regards and all

Urs

Urs Lauterburg
Physics demonstrator
Physikalisches Institut
University of Bern
Switzerland

From reberg@physics.umd.edu Tue Apr 26 09:53:21 2005

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