Re: Photons-atoms interactions

From: Kumar (lordshiva5753_at_rediffmail.com)
Date: 11/18/04 

Date: Thu, 18 Nov 2004 18:52:52 +0000 (UTC)

orcinus_orca@hotpop.com (Orcinus Orca) wrote in message news:<87e684ba.0411141611.25f4b8b0@posting.google.com>...
> lordshiva5753@rediffmail.com (Kumar) wrote in message
> > Thanks for reply. Frankly, I am trying to know that whether atoms can
> > absorb some energy & remain some excied for long time without emission
> > of photons.
>
> Yes they can. I just learned it yesterday. There are compounds called
> phosphors that manage to stay in excited states for quite a long time
> (hours). One example of a phosphor is zinc sulfide. An electron is
> excited by photons to a higher energy level and suffers a change in
> spin. It gets trapped in this higher energy orbital and cannot go back
> to the ground state. When this electron manages to absorb some heat
> (from the surroundings), it climbs to an even higher energy orbital
> and from this orbital it can go back to its ground state, emitting a
> photon. This is how glow-in-the-dark toys work.
>
> > However, we have to find out that whether atoms can trap/store some
> > energy for long time or not?
>
> Yes, phosphors can - they have the so called 'metastable state'. You
> can learn more if you do a search on phosphors or phosphorescence.
>
> > What atoms of tree do with other
> > wavelengths than green wavelength?
>
> Part of the photons absorbed is used for photosynthesis; the rest is
> lost vaporizing water (see below).
>
> > If it is lost as heat, how it
> > radiate/emit heat?
>
> Plants do not become hot despite sitting on the sun all day because
> they sweat just like we do ? it's called transpiration. The energy (in
> this case, heat) is used up to make water go from the liquid state
> inside plant to the gaseous state out to the atmosphere. A stone on
> the other hand will become very hot because it does not transpire. Its
> heat is lost to the environment (air and ground).

orcinus_orca,

Thanks. Now let us look at prism, it can absorb white light & emit
several wave lengths. Water can also create prism effect. Black colour
can also absorb several wavelengths. I want to know that atoms with
lower atomic numbers OR Carbon, Hydrogen & Oxygen as in water, alcohol
or sugar have some broad spectrum/several wavelengths absorbing
properties?

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