Future Project LaSpec within NUSTAR at FAIR

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Introduction

Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and excited state properties. Hyperfine structures, isotope and isomer shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates such studies in a model-independent manner.

At FAIR the Super Fragment Separator (SFRS) will provide a rich spectrum of isotopes that are not and will not be available at any other facility. From the view of optical spectroscopic research the proposed facility will afford unique access to regions of particular nuclear interest that would otherwise remain inaccessible. The proposed research of the LaSpec collaboration is thus not in competition with that of other facilities but will rather study complementary or entirely new cases. As highlighted in the LOI these cases include the study of isotopes of refractory elements, high-K isomers and a vast region of heavy, neutron-rich isotopes.

The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with ß-delayed neutron detection) has been achieved with rates of only a few atoms per second. At FAIR it will be possible for our collaboration to greatly extend our knowledge of nuclear sizes, deformation and electromagnetic moments far into the neutron-rich side of the upper part of the nuclear chart.

The LaSpec collaboration intends to construct a number of complementary experimental devices which will provide a complete system with respect to the physics and isotopes that can be studied:

• Collinear laser spectroscopy on ions
• Optical pumping and collinear laser spectroscopy on atoms
• β-NMR
• Resonance Ionization Laser Ion Source (RILIS)
• Laser-Desorption Resonance Ionization (LDRIS)
• Spectroscopy in an Electron Beam Ion Trap (EBIT)