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HK: Fachverband Physik der Hadronen und Kerne

HK 7: Nuclear Astrophysics I

HK 7.5: Talk

Monday, March 16, 2026, 17:30–17:45, PHIL A 602

Nuclear two-photon decay investigation of 98Mo in the ESR Heavy Ion Storage Ring — •Carlo Forconi for the E0018 Experiment collaboration — GSI Darmstadt, Germany

The nuclear two-photon or double gamma (2γ) decay is a rare second-order electromagnetic process in which an excited nucleus emits two gamma rays simultaneously. Its branching ratio is significantly lower than that of competing first-order processes such as internal conversion, pair creation, or single-photon emission, making its experimental observation extremely challenging. However, in the ESR at GSI, these competing decay modes can be suppressed by storing fully ionised ions and selecting a 0+ - 0+ transition with excitation energy below the electron-positron pair creation threshold (1022 keV). Under these conditions, the two-photon decay becomes the only available decay channel. In this talk, I will report on the current status of the analysis of an experiment investigating the 2γ decay of 98Mo, which has a first excited 0+ state at 734.75keV. The experiment was performed at the GSI facility in Darmstadt, where fully stripped 98Mo ions were produced using the projectile fragmentation of 100Mo primary beam on 9Be target in the transfer line. These ions were then transported and stored in the ESR, operated in the isochronous mode. Two non-destructive Schottky detectors were used, allowing for precision measurement of the ions revolution frequencies and extraction of both the nuclear half-life and mass. Preliminary results indicate that the measured half-life of 98Mo is consistent with the expected theoretical extrapolation estimates from previously studied 0+ - 0+ nuclear transitions.

Keywords: Lifetime measurement; Experimental Storage Ring; Schottky Detectors; Radioactive decay; Gamma emission