Q1(f). K and L lines in XRF; wavelength-dispersive spectrum of Zn

Answer in brief

Primary X-rays eject an inner-shell electron; an outer electron fills the vacancy and a characteristic X-ray is emitted: K lines for a K-shell vacancy (Kα from L, Kβ from M), L lines for an L-shell vacancy. Zn: Kα 1.435 Å, Kβ 1.295 Å.

Key points

• Primary X-rays above the absorption edge eject an inner-shell electron; an outer electron fills the vacancy and emits a characteristic (fluorescent) photon.
• K lines: Kα is L → K (2p → 1s), Kβ is M → K (3p → 1s); Kβ has higher energy and is weaker.
• L lines: vacancy in the L shell; used for heavy elements (Z above about 50) whose K lines are hard to excite.
• Zn (Z = 30): Kα 1.435 Å (8.64 keV), Kβ 1.295 Å (9.57 keV); K absorption edge 1.283 Å (9.66 keV).
• WDXRF: analysing crystal (nλ = 2d sin θ); with LiF(200), Zn Kβ at 2θ = 37.5°, Zn Kα at 2θ = 41.8°.