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Phys Rev Lett. 2012 Feb 3;108(5):052504. doi: 10.1103/PhysRevLett.108.052504. Epub 2012 Jan 31.
The first direct mass measurement of {6}He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of {8}He was determined with improved precision over our previous measurement. The obtained masses are m({6}He)=6.018 885 883(57) u and m({8}He)=8.033 934 44(11) u. The {6}He value shows a deviation from the literature of 4σ. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) and 1.959(16) fm for {6}He and {8}He, respectively. We present a detailed comparison to nuclear theory for {6}He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.
利用 ISAC 设施中的 TITAN 彭宁阱质谱仪，首次对{6}He 进行了直接质量测量。此外，我们对{8}He 的质量进行了比以前更精确的测量。得到的质量分别为 m({6}He)=6.018885883(57)u 和 m({8}He)=8.03393444(11)u。{6}He 的值与文献值的偏差为 4σ。利用这些新的质量值和之前测量的原子同位素位移，我们得到了{6}He 和{8}He 的电荷半径分别为 2.060(8)和 1.959(16)fm。我们对{6}He 进行了详细的核理论比较，包括新的超球谐函数结果。质子点半径与两个中子分离能的相关图清楚地表明了三核力的重要性。
