TRIUMF, University of British Columbia, 4004 Wesbrook Mall, Vancouver, British Columbia V6T 2A3, Canada.
Phys Rev Lett. 2012 Jul 20;109(3):032506. doi: 10.1103/PhysRevLett.109.032506.
We present precision Penning trap mass measurements of neutron-rich calcium and potassium isotopes in the vicinity of neutron number N=32. Using the TITAN system, the mass of 51K was measured for the first time, and the precision of the (51,52)Ca mass values were improved significantly. The new mass values show a dramatic increase of the binding energy compared to those reported in the atomic mass evaluation. In particular, 52Ca is more bound by 1.74 MeV, and the behavior with neutron number deviates substantially from the tabulated values. An increased binding was predicted recently based on calculations that include three-nucleon (3N) forces. We present a comparison to improved calculations, which agree remarkably with the evolution of masses with neutron number, making neutron-rich calcium isotopes an exciting region to probe 3N forces.
我们呈现了在中子数接近 N=32 的区域内富含中子的钙和钾同位素的精确彭宁阱质量测量结果。使用 TITAN 系统，首次测量了 51K 的质量，并且（51,52）Ca 质量值的精度得到了显著提高。与原子质量评估中报告的值相比，新的质量值显示出结合能的显著增加。特别是，52Ca 的结合能增加了 1.74 MeV，并且与中子数的关系偏离了表列值。最近的计算预测增加了结合能，这些计算包括三核子（3N）力。我们将其与改进的计算进行了比较，这些计算与质量随中子数的演化非常吻合，使得富含中子的钙同位素成为探测 3N 力的一个令人兴奋的区域。
