Development of a Compact Resonance Ionization Mass Spectrometer for Trace Element Analysis of Potassium

Abstract

A compact resonance ionization mass spectrometer is developed using two laser diodes and a quadrupole mass spectrometer to perform trace element analysis of potassium. With the help of a narrow linewidth of the laser diode, the isotope shifts of ${}^{40}\mathrm{K}$ and ${}^{41}\mathrm{K}$ of the 405 nm line with respect to ${}^{39}\mathrm{K}$, corresponding to the transition of $4{}^2$S${}_{1/2}\to$ $5{}^2$P${}_{1/2}^{\circ }$, are measured to be $207\pm 13$ MHz and $451\pm 10$ MHz, respectively, by comparing them to the known hyperfine splitting widths of the $4{}^2{\mathrm{S}}_{1/2}$ ground state of each potassium isotope. The overall detection efficiency of an order of $\sim 10^{-6}$ in our setup indicates the availability of RIMS to the analysis of the trace metal impurities on or in a certain material such as the contamination assessment of semiconductor wafers.

9 pages, 4 figures