     
Some important phenomena in
the atomic world
 
 
Zeeman effect, Paschen-Back
effect & Stark effect
We see that, the electron
configuration in an atom is determined by three factors. a) Attractive force
from the nucleus, b) repulsive forces between electrons c) buoyant force by
space matter. When an atom is placed in a strong electric or magnetic field,
its electron configuration is altered from the atom’s normal state. That is,
some of the electrons in the electron shells are shifted to inner or outer
transitory shells by the influence of the external field.
When such an atom is excited,
it will emit radiations with the natural frequencies of the ‘newly created
electron shells’ and other transitory shells. The Zeeman Effect is the
direct indication of strength of the magnetic field. I.e. when a weak field
affects only outer electrons, a stronger field influences both the inner and
outer electrons. Also, lighter elements can demonstrate Zeeman Effect in a
weak field comparatively than heavy elements, because of the electrons in a
lighter atom are loosely binded than that of a heavy atom.
Absorption spectrum
Every shell (electron shells
and transitory shells) of an atom has its own unique natural frequency (or
resonant frequency). When a cooled gas is placed in the path of continues
spectrum of light, dark absorption lines will be appeared in the resulting
spectrum. This absorption lines are caused by the absorption of that
particular frequencies by the gas atoms. That means the natural frequencies
of some of the electron shells and primary transitory shells of the gas
atoms are same as the frequencies of the absorbed spectrum lines.
Emission spectrum
If the same gas is examined
at an oblique angle, bright emission lines will be visible against a dark
background. The emission spectrum lines are caused by the reflection of
light (that absorbed by the gas atoms) by the electrons in the above stated
shells. That is, the emission lines are purely the reflection of light from
the gas atoms by its electrons. If we can make the whole of the absorption
spectrum lines or emission spectrum lines of an atom in all frequencies from
Infrared rays to X-rays at their cooled state (non-excited state), we can
directly observe the natural frequencies of each of the electron shells and
the primary transitory shells of that atom. The total number of electron
shells and the primary transitory shells in an atom are equal to the total
number of absorption or emission spectrum lines. And the natural frequencies
of the electron shells and primary transitory shells are, if we consider the
emission lines, then the highest frequency line for the innermost electron
shell and the lowest frequency line for the outermost primary transitory
shell. Same as, if we consider the absorption lines, then the highest
frequency absorption line for the innermost electron shell and the lowest
frequency absorption line for the outermost primary transitory shell.
Band spectra
Band spectra are produced
when the emitting substance is in the molecular state; therefore they are
also called molecular spectra. When atoms are bonded together to form a
molecule, the natural frequencies of the overlapped space matter shells are
altered from their original natural frequencies. So, a molecule of a
substance emits its own unique band spectra when it is excited and we can
identify a molecule by analyzing its band spectra.
Mechanism of reflection
(reflection of light)
The binding energy of 'light
reflecting electrons' to its atoms / molecules or to the surface of a light
reflecting material will be equal to or greater than that of the energy of
incident photons. When light falls on these electrons, they will oscillate
with the frequency of the incident photons and the light will be reflected.
Photoelectric effect
In an external photoelectric
effect, electrons are liberated from the surface of a metallic conductor by
absorbing energy from light shining on the metal’s surface. In this case,
the binding energy of photoelectrons (electrons that are liberated) to the
metal surface will be always lower than the energy of the incident photons
that causes the photoelectric effect. The kinetic energy of a photoelectron
is depends on the energy (frequency) of the incident photon. When energetic
photons fall on the low binding energy electrons in the metal surface, they
will oscillate with the frequency of incident photons. This oscillation
causes, the oscillating electrons induce its oscillations to the
elastic-outer shells of nearby atoms that in the metal surface. This
oscillations of outer shells of the atoms cause, it to expel (kick) the low
binding energy electrons from their surface. The kinetic energy of a
photoelectron increases with the increasing of the frequency of incident
photon. That is, as the ejection of photoelectrons are purely because of the
elasticity of outer shells of atoms, as the energy of incident photons
increases, the atoms kick the electrons with more kinetic energy.
Thermionic emission
We see that atoms are highly
elastic and vibrations and elastic collisions between atoms cause the
temperature of a material. As the thermal vibration of atoms in a material
increases, its atoms kick out the low binding energy electrons the material.
This is the reason for the Thermionic emission.
Compton Effect
Compton Effect
occurs when a high-energy photon falls on an atomic electron, which with
having a binding energy lowers than the energy of incident photon. We see
that, every electron shell in an atom has its own unique natural
frequency. When a high frequency photon falls on an electron that in an
electron shell which with having a natural frequency less than that of the
frequency of incident photon, because of an atomic electron can only
oscillate in the natural frequency of its electron shell within that shell,
the electron will oscillate in the natural frequency of its shell, and a
photon with the natural frequency of that electron shell is emitted at an
angle to the direction of the path of the incident photon. This emission of
the photon, which has a long wavelength than the incident photon, is the
Compton photon. We see that, when an electron is excited, it will jump from
an inner region to an outer region in the atom. So, the Compton electron
will jump at an angle to the direction of the path of the incident photon.
Pair production
The pair production is one of
the most interesting demonstrations for the presence of space matter in
atoms. When a gamma ray photon with the energy of 1.2 MeV is passed through
near a heavy nucleus (that is, through the innermost transitory shells) it
can result the production of one electron and one positron. The quantity of
space matter that closer to a heavy nucleus is equal to or more than the
mass of one electron and one positron, because of its high density at these
region. When such an energetic gamma ray photon is passed through the
high-density space matter region, the individual space matter units will be
bonded together to produce the electron-positron pair. When a pair
production occurs, the equal amount of space matter (with the mass of one
electron and one positron) will be entered from outside of the atom and the
natural densities of the space matter in the atomic shells will be always
maintained.
Primakoff effect
Primakoff effect (the
resonant production of neutral mesons by high-energy photons interacting
with an atomic nucleus) is also an evidence for the space matter in atoms.
|