Direct observation of the ${}^2\mathrm{D}_{3∕2}\text{−}{}^2\mathrm{D}_{5∕2}$ ground-state splitting in ${\mathrm{Xe}}^{9+}$

We have used an electron beam ion trap to observe a visible line at that corresponds to the magnetic dipole transition within the ground state configuration of . We have found no evidence to support the claim by others that a line near this position originates from . The comparison of the measured wavelength with previous indirect experimental values, and the dependence of the line intensity on the electron beam energy, confirms the validity of the present identification. Our measured wavelength is in agreement with semiempirical Hartree-Fock calculations but shows a discrepancy with multiconfiguration Dirac-Fock calculations. We propose that the line may be useful as a diagnostic for extreme ultraviolet lithography light sources.

Figure 1

Spectrum around the $598\mathrm{nm}$ region with and without xenon gas injection at $220\mathrm{eV}$ electron impact energy.

Figure 2

Line positions at different electron impact energies. One-sigma statistical uncertainties are shown as error bars on the individual points; the estimated systematic uncertainty is $0.08\mathrm{nm}$.

Figure 3

Electron beam energy dependence of the intensity of the Xe line measured at $598.30\left(13\right)\mathrm{nm}$ wavelength. The data are normalized to the electron beam current. The dashed line shows a normalization of the data to the square of the electron beam current. The correct normalization should lie somewhere between these two limits. The inset shows the energy range extended to $8\mathrm{keV}$. Error bars are at the one-sigma level.