Ultraviolet light is electromagnetic radiation in a part of the spectrum between
X-rays and visible light, approximately 180 nanometers to 400 nanometers.
It differs from light only that it's wavelengths are too short to be seen
by the human eye. UV-A , or long-wave radiation is 315 nanometers and
above. UV-B, or medium-range radiation, is 280 nanometers to 315
nanometers. UV-C, or short wave radiation, is 280 nanometers and below.
The phenomenon known as fluorescence occurs at the subatomic level by a
process called electron excitation. Electrons are subatomic particles that
orbit the nucleus of an atom at specific distances known as electron
shells. These shells are arranged in layers around the nucleus, the exact
number of electrons and their shells depending on the type of atom
(element). The electrons contained in the shells nearest the nucleus carry
less energy than the electrons in the outer shells.
When certain atoms are exposed to ultraviolet (UV) light, a photon
(particle of light energy) of UV will cause an electron residing in a
lower-energy inner electron shell to be temporarily boosted to a
higher-energy outer shell. In this condition, the electron is said to be
excited. It will then drop back to its original inner electron shell,
releasing its extra energy in the form of a photon of visible light. This
visible light is the fluorescent color that our eyes perceive. The exact
color depends on the wavelength of the visible light emitted, with the
wavelength itself being dependent on the type of atom undergoing the
electron excitation.
The specific atoms which undergo the fluorescence are known as
activators. They are usually present as impurities in the normal molecular
structure of the mineral, but sometimes are an intrinsic part of the
mineral's composition. In fluorescent minerals, very often the activators
are cations, which are atoms or molecules which carry a net positive
charge (due to the loss of one or more electrons, each of which display a
negative charge). For example, the activator which causes the bright red
fluorescence of calcite is the manganese cation, Mn+2. The
"Mn" is the chemical symbol for the element manganese, and the
"+2" indicates a manganese atom which has lost two electrons and
therefore has a net positive charge. A cation which has lost two electrons
is also referred to as divalent; three electrons, trivalent; four,
quadrivalent, etc. Activators can also sometimes be anions (containing a
net negative charge).
Ozone is generated naturally by short-wave solar ultraviolet radiation,
and appears in our upper atmosphere (ozonosphere) in the form of a gas.
Ozone also may be produced naturally by passing an electrical discharge -
such as lightning - through oxygen molecules. Lightning is a perfect
example of making an abundance of O3 to purify the earth's atmosphere
Nature's way. Most of us have noticed the clean, fresh smell in the
outdoor air after a thunderstorm, or the way clothing smells after it's
been dried outside on a clothesline in the sun.
Oxygen, as we know, has two atoms. High voltage, as from lightning, breaks
these two atoms apart. Quickly, these atoms hop back together in threes
{O3}. Confused, these atoms do not like this arrangement and want
desperately to dissolve this uncomfortable trio. So as this O3 molecule
floats in the air, when one of the atoms spots a contaminant molecule to
attach itself to, it breaks away from the other two atoms. To its
surprise, this attachment is actually an attack on the contaminant and
creates a microscopic explosion. Both the contaminant and the atom are
destroyed. This leaves the other two atoms behind as pure oxygen {O2}
without the presence of the contaminant. The explosion changes the
contaminant into carbon dioxide and hydrogen, which we can breathe.
Should the O3 molecule not find a contaminant in its environment, it will
attack itself to change its configuration of O3 back to O2 (normal oxygen)
in 20 to 30 minutes at room temperature and normal humidity.
Short-wave solar ultraviolet radiation - ultraviolet light - is another
method used by many air purifier manufacturers. When ultraviolet light
rays collide with a contaminant such as carbon monoxide (CO) and nitrogen
oxides (NO2 and N2O) in the presence of oxygen (O2), ozone is produced.
Ozone reacts with and oxidizes pollutants it encounters, rendering them
harmless, while also removing odors. O3 loses one of its oxygen molecules
in this oxidation process, causing it to revert back to oxygen, leaving
behind pure, fresh air. Ozone can be effective against chemical sources,
bacteria, mold, odors, etc. Once a pollutant is oxidized by ozone, it is
no longer toxic, allergenic, or odor causing. As a result, even if an
oxidized contaminant remains in the air and is inhaled, it has no negative
effect. Microorganisms (such as mold spores or bacteria) that have been
exposed to ozone are no longer able to reproduce, which causes their
numbers to quickly diminish.