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

TL;DR

This paper presents a compact resonance ionization mass spectrometer using diode lasers for trace potassium analysis, measuring isotope shifts and demonstrating its potential for detecting trace impurities in materials.

Contribution

The development of a compact RIMS with diode lasers and quadrupole mass spectrometer for precise isotope shift measurement and trace element analysis is novel.

Findings

Measured isotope shifts of $^{40}{ m K}$ and $^{41}{ m K}$ with respect to $^{39}{ m K}$.

Achieved an overall detection efficiency of approximately 10^{-6}.

Demonstrated potential for trace impurity detection in semiconductor materials.

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 $^{40}{\rm K}$ and $^{41}{\rm K}$ of the 405 nm line with respect to $^{39}{\rm K}$, corresponding to the transition of $4\,^2$S$_{1/2}\rightarrow$ $5\,^2$P$^\circ_{1/2}$, are measured to be $207\pm13$ MHz and $451\pm10$ MHz, respectively, by comparing them to the known hyperfine splitting widths of the $4\,^2{\rm S}_{1/2}$ ground state of each potassium isotope. The overall detection efficiency of an order of $\sim10^{-6}$ 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.