In the beginning of the 20th centuryNiels Bohr created the theory which described the behavior
of the electron circulating around the atomic nucleus. But it didn't explain the cause
of such behavior. It didn't explain way electron can take only some define orbits - the
stationery orbits. Many scientists worked over this problem.
In 1925 Louis Victor de Broglie (1892-1987) suggested that there
is a wave connected with the moving electron. The length of that wave as he said is equal:
(1)
where h is the Planck constant, p is the momentum of the
electron. The allowed orbits of an electron are those which perimeters are equal the
multiplied length of the wave of the particle.
Let's take a look on the de Broglie theory. It
was known that for the photons the momentum is connected with the wave length by the formula (1).
De Broglie noticed that the connection is also truth for the particles of matter. We can
substitute the momentum with the expression m*v, where m is the mass of the particle, v is
its velocity. So the expression for the wave length looks like shown below:
(2)
The formula shows that the particle of smaller velocity and the smaller
mass is characterized by longer wave length. Let's imagine the two examples:
The baseball ball of the mass of 0,14 kg is through by a pitcher with
the velocity of 40 m/s, after placing the data to the formula we get the wave length equal
1,2*10-34 m. It isn't much, actually even using the most modern technologies you
wouldn't see it.
From the other hand the electron moving with the velocity
of 40 m/s has the wave length equal 1,8*10-5 m. Such waves can be observed.
Not long after they showed that the electron could be connected
with the wave Heisenberg and Schrodinger described the waves mathematically.
Their formulas explain very well the observed experimental facts.
UUntil then the scientists imagined the electron as a very
small ball of a defined radius. The scientists of the 20tieths of our century gave the
description of the electron showing it being a wave and created a corpuscular-wave
picture of the electron. So the electron appeared to be both the small ball and the
wave. It doesn't behave as the thinks of the macro scale and the laws governing that
thinks are not through when talking about electron.
According to the new theory the electron should behave like a wave do.
So the electron should undergo interference and diffraction.
In 1925 Walther Erlasser noticed that if the electrons were connected
with waves they should undergo diffraction, when reflected from a crystal - exactly as the
X-rays did.
In 1925 Clinton Joseph Davisson (1881-1958) continued the researches
on the electrons scattered on nickel. Working over it he has an accident in his laboratory.
The bottle with liquid air exploded. The hot nickel which rapidly contacted air strongly
oxidated. After such conversion exterior part of the plate compounded of the much bigger
crystal than before. It occurred that the plate scattered the electrons in a completely
different way than before. That accident induced series of Davisson researches on the
electrons colliding monocrystals. He got interested with the Schrodinger works and using them he tried to
explain the phenomena. After he made many calculation and conducted many experiments in
the beginning of 1927 he noticed a strong beam surely caused by the
diffraction of electrons.
At the same time George
Paget Thomson (J.J. Thomson's son) also conducted
experiments on the electrons scattering. He also received diffraction.
In 1937 they both received the Nobel Prize.
In the fall of the 20thies of our century the theory of
wave-corpuscular structure of the electron was experimentally proofed after it
was formulated only a few years before. The scientists discovered that the one
of the basic components of atom is not so simple as they thought before.
The electron characterized both with the features of a particle and a wave.
The features of the electron are being used in different departments
of science (e.g. for construction of the electron microscope).
(1)
(2)
