Question

What is photoelectric effec when x ray interact with matter

Answer 1

Answer:Simply stated, the photoelectric effect occurs when photons interact with matter with resulting ejection of electrons from the matter. Photoelectric (PE) absorption of x-rays occurs when the x-ray photon is absorbed resulting in the ejection of electrons from the atom.

Answer 2

Answer:

Explanation:

The Photoelectric Effect

Simply stated, the photoelectric effect occurs when photons interact with matter with

resulting ejection of electrons from the matter. Photoelectric (PE) absorption of x-rays

occurs when the x-ray photon is absorbed resulting in the ejection of electrons from the

atom. This leaves the atom in an ionized (i.e., charged) state. The ionized atom then

returns to the neutral state with the emission of an x-ray characteristic of the atom. PE

absorption is the dominant process for x-ray absorption up to energies of about 500 KeV.

PE absorption is also dominant for atoms of high atomic numbers.

The photoelectric effect is responsible for the production of characteristic x-rays in the xray tube, but the process is also important as a secondary process that occurs when x-rays

interact with matter. An x-ray photon transfers its energy to an orbital electron, which is

then dislodged and exits the atom at high speed with a kinetic energy equal to:

KE = Ex - P

Where KE is the kinetic energy of the photoelectron

Ex is the energy of the incident X-ray photon

P is the energy required to remove the electron. This is equivalent to its

binding energy in the atom.

The energy equivalent of the rest mass of an electron is moc

2

, and is equal to about 0.51

MeV (mo is the rest mass of an electron and c is the speed of light). When Ex is much

lower than this value, the electron will exit at a high angle to the incident beam; when Ex

is closer to this value, the electron will exit at close to parallel with the beam.

When the photoelectron is ejected, it has the capability, depending on its energy, to

interact with subsequent electrons in other molecules or atoms in a chain reaction until all

its energy is lost. If that interaction results in the ejection of an outer orbital electron, this

is known as the Auger (au-jay) effect, and the electron called an Auger electron. The

probability of producing a secondary photoelectron vs. an Auger electron is directly

proportional to the KE of the photoelectron.

The production of photoelectric and Auger electrons is shown diagrammatically in the

following figure from Jenkins and Snyder (1996). In the diagram (a) shows the incident

X-ray photon, (b) shows the production of a high-energy primary photoelectron. In (c) a

lower energy electron moves into the vacated K-shell resulting in the production of an Xray photon that leaves the atom, and in (d) the X-ray photon is absorbed by an outer shell

electron resulting in the emission of a Auger electron.