Question

In Energy Dispersive Spectroscopy (EDS). Describe the difference between K, L, and M radiation using an energy level diagram.

Answer 1

Energy-dispersive spectroscopy is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on an interaction of some source of X-ray excitation and a sample. Its characterization capabilities are due in large part to the fundamental principle that each element has a unique atomic structure allowing a unique set of peaks on its electromagnetic emission spectrum(which is the main principle of spectroscopy). (Ref : wikipedia)

At ground state, the unexcited electrons rest at their normal energy states or shells. Once they receive energy from the excitation source they move up to higher shells according to current energy level. But after a short while, they lose the energy or part of the energy received in form of excitation and move back to their original shell or shell lower than the current stage according to the amount of lost energy (Note: for better understanding see Bohr's model). Meanwhile, they release the energy in the form of an electromagnetic wave (in form of radiation) to emit their characteristic wavelength(wavelength released by a particular element to jump from higher shell to some lower shell, which is unique for a particular element.) and move back to some lower energy level.

This lower energy level where the electron returns can be K, L, M, N etc. where K is the 1st shell, L is the 2nd shell, M is the 3rd shell and so on. Suppose an excited electron returns to K shell (shell no 1) from some higher shell (like 2, 3, 4,.... so on), it will release the radiation according to the energy gap between corresponding energy gaps of the two shells (say, an electron returns from shell 3 to shell 1, then the emitted radiation should have a wavelength corresponding to the energy gap between shell 3 and 1). Hence, an electron can jump to K shell from shells like 2,3,4,.... infinity and can have energy gap corresponding to 2-1, 3-1, 4-1, 5-1... so on. Hence a return to K shell releases emissions corresponding to those energy gaps, which can be found easily by the relation,

where m and n are two respective higher and lower shells among which the jump occurs and h = Planck's constant, c = speed of light and λ = wavelength.

when this n = 1 (K shell) and m = (some shell >1), i.e. electron jump is from some higher shell to K shell, the radiations emitted corresponding to these stages is known as K radiation.

Likewise,

when this n = 2 (L shell) and m = (some shell >2), i.e. electron jump is from some higher shell to L shell, the radiations emitted corresponding to these stages is known as L radiation.

and

when this n = 3 (N shell) and m = (some shell >2), i.e. electron jump is from some higher shell to N shell, the radiations emitted corresponding to these stages is known as L radiation.

The energy level diagram is provided below;

here in Energy level diagram, up to n = 5 is shown(O level). Energy level beyond that (n =6, 7, 8... and so on) exits and corresponding transitions to lower shells exist which will contribute further addition o K radiation, L radiation, M radiation, N radiation etc.