Measurement of the Isolated Nuclear Two-Photon Decay in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi>Ge</mml:mi> </mml:mrow> <mml:mprescripts/> <mml:none/> <mml:mrow> <mml:mn>72</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:mrow> </mml:math>
D. Freire-Fernández, W. Korten, Rui Jiu Chen, S. Litvinov, Yu. A. Litvinov, M. S. Sanjari, H. Weick, F. C. Akinci, H. M. Albers, M. Armstrong, A. Banerjee, K. Blaum, C. Brandau, B. A. Brown, C. G. Bruno, J. J. Carroll, Xiangcheng Chen, C. J. Chiara, M. L. Cortés, S. Dellmann, I. Dillmann, D. Dmytriiev, O. Forstner, H. Geißel, J. Glorius, A. Görgen, M. Górska, C. J. Griffin, A. Gumberidze, S. Harayama, R. Heß, N. Hubbard, K. Ide, Ph. R. John, R. Joseph, B. Jurado, D. Kalaydjieva, K. Kanika, F. G. Kondev, P. Koseoglou, G. Košir, C. Kozhuharov, Iu. N. Kulikov, G. Leckenby, B. Lorenz, J. Marsh, A. Mistry, A. Ozawa, N. Pietralla, Zs. Podolyák, M. Polettini, M. Sguazzin, R. S. Sidhu, M. Steck, Th. Stöhlker, J. A. Swartz, J. Vesic, P. M. Walker, Takayuki Yamaguchi, R. Zidarova
Abstract
The nuclear two-photon or double-gamma (2γ) decay is a second-order electromagnetic process whereby a nucleus in an excited state emits two gamma rays simultaneously. To be able to directly measure the 2γ decay rate in the low-energy regime below the electron-positron pair-creation threshold, we combined the isochronous mode of a storage ring with Schottky resonant cavities. The newly developed technique can be applied to isomers with excitation energies down to ∼100 keV and half-lives as short as ∼10 ms. The half-life for the 2γ decay of the first-excited 0^{+} state in bare ^{72}Ge ions was determined to be 23.9(6) ms, which strongly deviates from expectations.