Collisions of Electrons with Atoms

Collisions of Electrons with Atoms

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Atom and electron collisions are processes in which electrons can ionise an atom, removing electrons from its structure or excite electrons, thus moving them from one place to another in the areas in which they occur inside the atom. The initial state of the electrons, if they are stable, is named the ground state.When electrons collide with atoms, interesting things happen! Sometimes, the electrons can even remove other electrons from the atom, or make them move around inside it. Scientists call this process "ionisation" or "excitation." If the electrons are just hanging out and not doing much, they're said to be in the "ground state."

Electron collision with atoms and ionisation

Electrons can also initiate a beta decay to ionise or excite the electrons, a process that depends on:

The energy of the incident electron, which is given by its kinetic energy.The energy of the electrons moving around the atom.

To remove an electron from an atom requires energy, because the electron is  attracted to the protons, but I don't understand why photon/energy would be  released when an electron is added to
When an electron or a photon impacts an atom, part of their kinetic injects energy into the electrons orbiting around the atom

What happens when an atom and electrons collide?

When a photon hits an atom, or when an unstable isotope breaks apart, electrons can break free. These speedy electrons can then collide with other atoms, which can cause three different things to happen:

  1. Excited electrons: Sometimes, the electron that collides with an atom gives its energy to another electron in the atom. This can make that electron move to a new orbit, which is called an "excited state."
  2. Ionisation: The speedy electron can knock other electrons out of the atom, which makes the atom more positively charged.
  3. Proton-neutron conversion: If the atom captures an electron, a proton can turn into a neutron. This is called "beta plus decay" and it releases a positron, which is like a positive electron.

What happens when an electron collision excites another electron?

When an electron collides with an atom, it can excite another electron. This happens when the electron that's moving fast gives some of its energy to another electron that's already orbiting the atom. Before it got hit by the speedy electron, that electron was probably in the "ground state."

Electron or photon impacting and exchanging energy with an electron in a ground state
Electron or photon impacting and exchanging energy with an electron in a ground state

As the electron that lives in the atom is bound to its location with some fixed energy, the energy excess given by the other electron makes it jump to another energy level.

Electron jumping to an excited state after absorbing energy from the incident electron or photon
Electron jumping to an excited state after absorbing energy from the incident electron or photon

The electron will stay in an excited state for some time. However, as the atom seeks to be stable, the electron eventually releases its excess energy as a photon. After releasing the excess energy, the electron reverts to the ground state and its initial energy level.

Electron jumping back from an excited state and releasing energy as a photon
Electron jumping back from an excited state and releasing energy as a photon

Calculating the energy levels after electron collisions

When an electron collides with an atom, it can transfer some of its energy to an electron orbiting the atom, causing that electron to jump to a higher energy level. If we use the energy conservation law, the energy of the incoming electron can be calculated to be equal to the difference between the two energy levels.

For example, let's say an electron with a kinetic energy of 10.2 electron volts collides with a hydrogen atom. The electron in the atom will jump to the n=2 energy level, which is the first excited state.

However, the first excited state is unstable, and the atom will release the excess energy in the form of a photon. The energy of the photon will be equal to the energy gained by the electron when it jumped to the higher energy level. This energy can be calculated using the photon's energy equation, where f is the photon's frequency and h is the Planck constant.

To determine the frequency of the photon released after the electron jumps back to its ground state, we can use the equation E=hf, where E is the energy of the photon. In this case, the energy of the photon is equal to the energy used to move up, which is 1.63 x 10^-18 joules or 10.2 eV.

Using this equation, we can calculate the frequency of the photon to be approximately 1.22 x 10^15 Hz. We can further determine the wavelength of the photon using the photon-wavelength-frequency relationship. The wavelength of the photon is found to be approximately 0.12 micrometres, which is within the range for UV light.

As for the electron that caused the other electron to jump, it ends up with a velocity of 0 after the collision.

Wavelengths and frequencies for common types of photons

Photons can be categorized based on their frequency and wavelength. The speed of light in a vacuum is represented by ‘c’ in an equation that can be used to convert between photon frequency and wavelength. When electrons or photons collide with atoms, they transfer energy to the electrons orbiting the atom, causing them to jump to higher energy levels or even be ejected. Electrons that are not excited are said to be in their ground state. When excited electrons return to their ground state, they release energy in the form of a photon.

Collisions of Electrons with Atoms

What do electrons collide with?

Electrons can collide with many other particles. These interactions can cause a range of processes. If the collision is with an atom, the electron’s kinetic energy can be transferred to an electron inside the atom and excite or eject it from the atom. If the electron is captured by the nucleus, a proton will combine with it, causing a beta plus decay.

What happens when neutrons and atoms collide?

Neutrons can impact an atomic nucleus. When this happens, the neutron imparts energy, which, if large enough, will break the atom in a process that produces radiation and lighter elements.

What happens when electrons collide with atoms?

When an electron collides with an atom, there is the probability that the electron will push out an electron orbiting the atom. This happens because the electrostatic force repels both, and the one orbiting feels enough force to be kicked out of the atom. This, in turn, makes the atom a positive ion.Another possibility is that the atom is positively charged (by lacking electrons) and captures an electron. In this case, the electron will remain in the atom, and the atom will release the electron’s excess kinetic energy in the form of a photon.

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