First application of combined isochronous and Schottky mass spectrometry: Half-lives of fully ionized ${}^{49}\mathrm{Cr}^{24+}$ and ${}^{53}\mathrm{Fe}^{26+}$ atoms

Lifetime measurements of $\beta$-decaying highly charged ions have been performed in the experimental storage ring (CSRe) by applying the isochronous Schottky mass spectrometry. The fully ionized ${}^{49}\mathrm{Cr}$ and ${}^{53}\mathrm{Fe}$ ions were produced in projectile fragmentation of ${}^{58}\mathrm{Ni}$ primary beam and were stored in the CSRe tuned into the isochronous ion-optical mode. The new resonant Schottky detector was applied to monitor the intensities of stored uncooled ${}^{49}\mathrm{Cr}^{24+}$ and ${}^{53}\mathrm{Fe}^{26+}$ ions. The extracted half-lives $T_{1/2}\left({}^{49}\mathrm{Cr}^{24+}\right)=44.0\left(27\right)$ min and $T_{1/2}\left({}^{53}\mathrm{Fe}^{26+}\right)=8.47\left(19\right)$ min are in excellent agreement with the literature half-life values corrected for the disabled electron capture branchings. This is an important proof-of-principle step towards realizing the simultaneous mass and lifetime measurements on exotic nuclei at the future storage ring facilities.

Figure 1

The heavy-ion storage ring CSRe. The Schottky resonator (see photo in the insert) is installed in a straight section of CSRe.

Figure 2

Typical Schottky frequency spectrum. The peaks are labeled with the corresponding isotope identification.

Figure 3

Peak areas normalized with the initial area ($S_0$) as a function of the time elapsed since the injection of ${}^{49}\mathrm{Cr}\text{−}{}^{50}\mathrm{Cr}$ and ${}^{53}\mathrm{Fe}\text{−}{}^{54}\mathrm{Fe}$ ions into the CSRe. The error bars represent statistical uncertainties of the peak areas extracted from the corresponding Gaussian fits. The solid lines represent fits with single exponential function. The data for ${}^{53}\mathrm{Fe}$ is fitted only starting from time $T>9$ min, when the isomers have mostly decayed. For details see text.