[Rockhounds] colour perception, organic fluorescence, etc

[Jim Daly]

Hi Axel,
I Hadn't read this before my last reply. This could be the explanation for the foxfire mechanism. Might also have been helpful to the American Cyanamid people, (if Cyanamid still existed)
Jim

--- On Sat, 12/13/08, Axel Emmermann <axel.emmermann at pandora.be> wrote:

From: Axel Emmermann <axel.emmermann at pandora.be>
Subject: RE: [Rockhounds] colour perception, organic fluorescence, etc
To: "'Rockhounds at drizzle.com: A mailing list for rock and gem collectors'" <rockhounds at lists.drizzle.com>
Date: Saturday, December 13, 2008, 12:06 PM

Hi Alan,

I know of one mechanisme that makes some organic compouds fluoresce;
It happens when energy is transferred between chemical groups that are part
of a molecule. 
If my memory serves me, rhodamine B is a good example (it used to be a
reagent to demonstrate antimony, it gives a violet precipitate).
Complex organic molecules vibrate (all molecules do). They can rotate,
vibrate and stuff. Some of these chemical groups of the rhodamine B molecule
exchange energy each time the "flexing" molecule brings these groups
close
together. So the electron that carries the energy just "walks" over
whenever
the gap is small. Hence, no fluorescence.
When you put it in the freezer, however, you drain some of the motion-energy
of the molecules, making them "less flexible". Now the electron has
to JUMP
the space and the rhodamine B becomes fluorescent.
It's called cryoluminescence.

Cheers

Axel

> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com]
> Namens Alan Goldstein
> Verzonden: zaterdag 13 december 2008 5:22
> Aan: jr50wv at yahoo.com; Rockhounds at drizzle.com: A mailing list for rock and
gem collectors
> Onderwerp: Re: [Rockhounds] colour perception, organic fluorescence, etc
> 
> I also noticed a difference in color between eyes. The sky was a different
> shade of blue between the left and right eye (slight but noticable).
Haven't
> looked for the difference in years, need to try it again. As a long time
> amateur astronomer I always had fun comparing the subtle colors of stars
and
> nebulae between different observers.
> 
> I also noticed the skyglow at night was different. If I observed with a
red
> light, the night sky had a green color. If I looked with purple (from a
bug
> light), the night sky had a deep red hue. Fun stuff! My observing buddies
> noticed the effect, so it wasn't just me. I was the one to point it
out.
> 
> Poison sumac is a northern plant, not western. It is widespread in
northern
> Indiana. Poison oak is the western plant.
> 
> Alan
> 
> ----- Original Message -----
> From: "J. R. Hodel" <jr50wv at yahoo.com>
> To: <rockhounds at lists.drizzle.com>
> Sent: Friday, December 12, 2008 9:11 PM
> Subject: [Rockhounds] colour perception, organic fluorescence, etc
> 
> 
> HI Axel, Kitty, et al:
> 
> Someone remarked about color perception, and this not only varies between
> people but between eyes. Now I'll date myself . . . Back in the day
when I
> spent a lot of time in a darkroom and comparing color results from film
> batch to batch, and from video camera to video camera despite the best job
> the color engineers could do, I noticed that my eyes had slightly
different
> color responses. Partly this was noticable because back then you aimed a
> film camera with one eye at the viewfinder.
> 
> One eye was closer to Ektachrome and one was closer to Kodachrome - go
> figure. It's less noticable now, but still there. So comparing colors
of
> phosphorescence and fluorescence with the naked eye and discussing it via
> email may be futile. Surely the color business has sensors that make this
> all objective nowadays?
> 
> Axel, here in the North American forests we have several woods that
> fluoresce under the right stimulation. Locust (I think the black locust
> variety native to the WV forest) glows, as does the shrub sumac. This
isn't
> the poison sumac which I think is a western shrub, this is a shrub which
> bears bright red fruit clusters with which you can make a pleasent
> non-intoxicating beverage. It glows best in long-wave "black
light". I
don't
> remember which spectrum locust responds to best.
> 
> Do we know what mechanism might cause the fluorescent reaction in organic
> materials?
> 
> Just wondering, sorry if we're off topic, but it is related to black
light,
> etc.
> 
> Merry Christmas, everyone!
> 
> JR
> 
> 
> 
> 
> 
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