1. Muonic Atoms
I’d like to talk to you about muonic atoms.

2. to produce the muon… or or where p: the proton n: the neutron
π:the pion 　ν:the neutrino
μ:the muon
To produce the muons, the following reactions occur!
At first, as this reactions, matter is bombarded with energetic protons (about 440 MeV), giving rise to the pions.
Next, according to this reactions, the pions decay into the muons.
By the way, the half-life for this decay is 2.5×10^(-8)[s] (2 point 5 times 10 to the minus eighth -seconds).

3. The nature of Muon Muons have a charge e, a mass equal to 207･m0
Muons themselves decay.
Next, I’ll talk about the characteristics of muons.
The muonic atoms, first observed in 1952, can be described with the simple Bohr model.
Muons have a charge e, and a mass of muons is about 207 times heavier than electrons’.
Then, according to this reactions, muons decay into electrons or positrons.
The half-life for this delay is 2.2×10^(-6)[s].

4. Before Muons decay, they are captured into atomic orbits and occupy the orbits of electrons.
They make transitions from the outer to inner orbits.
Before muons decay, they can be captured into outer atomic orbits by atomic nuclei and can occupy these orbits in the place of electrons.
Then, the muons make transitions from the outer to inner orbits.
And then, they radiate light of the corresponding atomic transition frequency. This light is in the x-ray region of the spectrum.
They radiate light in the x-ray region of the spectrum.

5. Muons behave like heavy electrons. ~Bohr model ex. 12Mg electrons:
　　　Muon is closer to the nucleus than electron.
Muonic atoms are objects of the nuclear physics research.
The quantum energy in a muonic atom is larger by the ratio of the masses than the energy of transition in an electronic atom.
Since muons behave like heavy electrons, we can simply apply the results of the Bohr model.
rn is the radius of orbit in the Bohr model. This value depends on the electron or muon mass.
For example, the radii of magnesium atoms are as these expressions.
・electrons’ radius is
4.5×10^(-12)[m].
・muons’ radius is
2.2×10^(-14)[m].
Like this, the muon is much closer to the nucleus than the electron.
And then, the quantum energy is larger by the ratio of the masses than the energy of the corresponding transition in an electronic atom.
Finally,Muonic atoms are objects of nuclear physics research.
Since the muons approach the nucleus very closely, muons can be used to study details of the nuclear charge density distribution and nuclear quadrupole deformation.

6. Muonic terms diagram for an atom with Z=60
This energy transitions are similar to the hydrogen atom.
The energy scale is MeV unlike the hydrogen.
This figure shows a term diagram of the muonic-atom levels for a nuclear charge number Z=(equals)60.
The fully drawn levels correspond to the assumption of a point nucleus.
The dushed levels take account of the finite nuclear size.
The transitions are in the energy of MeV; that is in the region of hard x-rays and of gamma rays.
By this figure, the analogy with the hydrogen atom is obvious.

7. Summary ~Muonic atoms
Muons have a charge e and behave like heavy electrons.
　Therefore, we can apply the Bohr model.
Muons are produced in decaying pions.
Muons themselves decay.
~or else
They are captured by atomic nuclei, make transitions, and radiate light.
Let me summarize this contents!
Muons have a charge e, and behave like heavy electrons.
Therefore, we can apply the results of the Bohr model.
Muons are produced in decaying pions.
Then, muons themselves decay into electrons or positrons, or else they are captured by atomic nuclei, make transitions from the outer to inner orbits, and radiate light of the corresponding atomic transition frequency.

8. Excitation of Quantum Jumps by Collisions
Next, I’d like to talk to you about the excitation of Quantum Jumps by Collision.
I intend to show you as follows: first, the research into the ionization of atoms by electron collisions, second, the experiment by Franck and Hertz, third, the improvement of the experiment, and finally, I’ll summarize this contents.

9. the ionization of atoms by using electron collisions
Ionization events are detected as a current to the plate.
This left figure shows experimental arrangement for detecting ionization process in gas by Lenard.
~process~
Now, I’ll talk about a physical phenomenon in this arrangement.
The free electrons produced by thermionic emission are accelerated by the positive grid VG, and then the electrons pass through the open-meshed grid into the experimental region.
The plate A is negatively charged compared with the grid.
The voltages VA are chosen so that the electrons cannot reach the plate.
When an electron has ionized an atom of the gas in the experimental region, the ion is accelerated towards the plate A.
I mean ionization events are detected as a current to the plate.
This right figure shows the current as a function of the grid voltage VG.
Vi is the voltage with which the electrons must be accelerated so as to ionize the atoms.

10. Franck-Hertz’s experiment
5eV
This left figure is the experiment arrangement of Franck-Hertz for investigating inelastic collisions between electrons and atoms.
I’d like to explain this process in next sheet.
This right figure shows the current as a function of the grid voltage VG. When the electrons reach an energy of about 5eV, they can give up their energy to a discrete level of the mercury atoms.
Then the current I is strongly reduced.
When their energy becomes 10eV, this energy transfer can occur twice…
Indeed, one observes an intense line in emission and absorption at E=4.85eV in the optical spectrum of atomic mercury.

11. ~process~ electrons are accelerated inelastic collisions
~up to a grid
inelastic collisions
(between electrons and atoms)
gas atoms receive the energies partially or completely from electrons
electrons lose most of kinetic energy
they fall back to the grid by a braking voltage VB
I intend to speak about the physical phenomenon in this arrangement.
Electrons from a heated cathode are accelerated by a variable voltage VG.
They pass through the grid, and then inelastic collisions between electrons and atoms can occur!
On one hand, electrons lose most of their kinetic energy in inelastic collisions in the gas-filled space, and fall back to the grid.
On the other hand, gas atoms receive the kinetic energies partially or completely from electrons.
The anode current is then measured as a function of VG at a constant braking potential VB.
the anode A current is measured

12. Improved experimental setup in Franck-Hertz’s experiment
Please look at this figure.
By using an indirectly heated cathode and a field-free collision space between the two grids in Franck-Hertz’s experiment, the resolving power “what is called, resolution” for the energy loss of the electrons are improved.
Now, between the two grids, the voltage is constant.
as this right figure, with an improved experimental arrangement, a number of structures can be seen in the current-voltage curve.
Now,I’d like to give a particular account of the resolution and energy of loss. The resolution is the power to distinguish a slight difference of energy.
Let us suppose that the grid is one!
The energy when electrons collide the atoms and slow down and are accelerated by the VG,
the energy when electrons are accelerated without colliding the atoms.
If the two energies are nearly equal to each other, the two aren’t distinguished.
But then, we use the two grids, and since the voltage is constant between the two grids, this trouble can vanish.

13. Summary
Electron collision experiments prove the existence of discrete excitation states in atoms.
Franck-Hertz’s experiment establish the Bohr’s postulates.
Let me summarize this contents.
These electron collision experiments prove the existence of discrete excitation states in atoms independently of optical-spectroscopic results.
Then, these facts offered an excellent confirmation of the basic assumptions of the Bohr theory.
That’s all.
Thank you very much for your kind attention.
Do you have any questions or comments?