New mass value for 7Li

Area of Science:

• Nuclear Physics
• Atomic Physics
• Metrology

Background:

• Accurate atomic mass values are fundamental for nuclear structure studies.
• Previous evaluations of the Lithium-7 (7Li) atomic mass may require revision.
• High-precision mass spectrometry is crucial for testing fundamental physics theories.

Purpose of the Study:

• To perform a high-accuracy mass measurement of Lithium-7 (7Li).
• To compare the measured mass with existing literature values, specifically the Atomic-Mass Evaluation 2003 (AME 2003).
• To discuss the implications of the revised 7Li mass for nuclear charge radii and neutron halo nuclei.

Main Methods:

• Utilized the SMILETRAP Penning-trap mass spectrometer.
• Employed a cyclotron frequency comparison technique.
• Measured the frequencies of Lithium-7 ions (7Li3+) and molecular hydrogen ions (H2+).

Main Results:

• Determined a new atomic mass value for 7Li: 7.016 003 425 6(45) atomic mass units (u).
• Achieved a high precision with a relative uncertainty of 0.63 parts per billion (ppb).
• Observed a significant deviation of 14 sigma (1.1 micro-u) from the AME 2003 value.

Conclusions:

• The new, highly accurate 7Li mass value challenges the established AME 2003.
• This revised mass is critical for calibrating measurements of nuclear-charge radii.
• The improved 7Li mass value is essential for future atomic mass measurements of neutron-rich isotopes like 9Li and 11Li.