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Trap assisted spectroscopy and mass measurements at ISOLTRAP

Final Activity Report Summary - TASMATI (Trap assisted spectroscopy and mass measurements at Isoltrap)

TASMATI is a two-year project devoted to unveiling the mysteries of the atomic nucleus with use of ion traps and lasers. Although investigated since many years, the tiny atomic nucleus still holds many unresolved secrets. We do not know well the limits of existence of nuclei, when protons and neutrons are added together; we are not certain how and where some of the chemical elements were produced in stars; we would like to understand why the present Universe looks the way it does today.

To address these fundamental questions I worked at a "factory" of short-lived isotopes, ISOLDE. Located at the CERN laboratory in Geneva, ISOLDE can produce over 3000 nuclides with a different number of protons and neutrons, even as exotic as lithium-11, built of 3 protons and 5 more neutrons and living on average only 9 milliseconds before it transforms into beryllium-11. Research conducted within this project is quite interdisciplinary: it collects information about the interaction of protons and neutrons inside the nuclei by using atomic physics techniques: ion traps and lasers. We look at the response from atomic nuclei when we store them in ion traps and manipulate them with radio-fields, or when exciting the electrons around them with laser light.

For the TASMATI project, we used the traps in a unique way to select only the ions of interest, and to send them further to a system which allows looking at their decay properties, i.e. what is the energy, time and space distribution of the beta particles and gamma radiation emitted when they transform into other nuclei. From this information we can learn about the structure of both the mother and the daughter nucleus. The system is now ready for the first experiments. Within TASMATI we also used the laser light to determine the charge radii of light beryllium isotopes, especially Be-11 where the last neutron forms a halo and stays far away from the other 6 neutrons and 4 protons. Our studies act indirectly like an extremely precise microscope: they allow estimating that the halo neutron stays about 7 femtometres (7 times 1/1,000,000,000,000,000 of a meter) away from the rest of the nucleons, which can be very well reproduced by several models of light nuclei. In addition, we performed many mass measurements. We looked at cadmium isotopes which are very rich in neutrons and are important in the creation of nuclei in stars via a capture of a neutron. We studied a close-to-stable mercury-194 and its daughter gold-194, which can help to determine the unknown mass of the neutrino particle, which interacts so weakly with matter that we hardly notice its existence. Until recently we even thought that it has no mass, just like the light carrier, the photon. During studies on radon isotopes, we even identified a new nuclide, radon-229 with 86 protons and 143 neutrons, measured its mass the lifetime. This discovery will help to refine predictions concerning the borders of existence of heavy nuclei.

The experience gained and equipment built during the TASMATI project with serve also in the future to perform studies on exotic nuclei, and will contribute to our understanding of the mysterious atomic nucleus. And who knows, maybe one day it will be even used in our daily lives.