# X - rays

1. Aug 10, 2010

### mccoy1

Hi guys, I don't know if this question has been asked before, but I searched the forum but didn't get answer to my question. I was looking at the transition when a core electron is knocked off by energy and that an upper level electron replaces it and x ray is released. Question, why are there 2p lines (instead of 3) and 2d lines (instead of 5 orbitals)?
I'd appreciate your input.
Thanks

2. Aug 10, 2010

### mccoy1

bump....46 views and no a single reply

3. Aug 10, 2010

### Gokul43201

Staff Emeritus
Maybe people are having a hard time understanding your question. Can you include a figure of the emission spectrum are rewrite your question in the context of the figure?

4. Aug 10, 2010

### mccoy1

oh okay. First of all, thanks for the reply. I don't have a diagram here because i'm using a mobile phone. I was talking about x-rays energy diagram. Usually they have K, L, M etc shell. Take M shell for example. The lines shown are one 3s, two 3p, two 3d. So what i don't get is the fact that only 2 p-energy levels are drawn instead of 3(because p has 3 subshell, not two. Same for d, only 2 likes instead of 5. Thanks

5. Aug 11, 2010

### Bob S

This might help.
Suppose a core electron (in the 1s shell) is knocked out by deep core photoejection. The only allowed atomic electron transitions to fill the empty 1s state are δl = 1 transitions, i.e., from 2p, 3p, 4p, etc.

In looking at the transition rates (inverse lifetimes) for 2p-1s, 3p-1s, 4p-1s, etc. in the single-electron hydrogen atom, they are 6.25 x 108, 1.64 x 108, 0.68 x 108 sec-1 respectively, implying that the 2p-1s transition is the most likely.

Bob S

6. Aug 12, 2010

### DrDu

Keep also in mind that the 3 p orbitals or the 5 d orbitals are energetically degenerate in zeroth order. They may split into two groups (term components) due to spin-orbit interaction. There is only one term $$^3S_{1/2}$$ for the primary hole formed in the K shell. While for a hole in a p or d subshell there are two possibilities, $$^2P_{1/2}$$ and $$^2P_{3/2}$$ for a hole in the p-shell and $$^2D_{3/2}$$ and $$^2D_{5/2}$$ in the d-shell, respectively. This is due to the two possibilities to combine spin with the orbital angular momentum, i.e., J=L+S and J=L-S.

7. Aug 13, 2010

### mccoy1

Thank you very much DrDu..You hit the nail on the head. I didn't know that those states arise from the microstates because they just label them K, L, M, L which is not very informative.
Thank you too Bob S.