Nuclear charge radius of 8He.
P Mueller1, I A Sulai, A C C Villari
1Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. pmueller@anl.gov
Physical Review Letters
|February 1, 2008
Summary
The nuclear charge radius of 8He was measured for the first time, revealing a smaller size than 6He. This finding supports the predicted neutron halo structure in 8He, impacting nuclear physics understanding.
Area of Science:
- Nuclear Physics
- Atomic Physics
- Quantum Chemistry
Background:
- Understanding the structure of exotic nuclei like helium isotopes is crucial for nuclear theory.
- Neutron-rich nuclei exhibit unique properties, such as the potential for neutron halo structures.
Purpose of the Study:
- To determine the root-mean-square (rms) nuclear charge radius of the exotic 8He nucleus for the first time.
- To precisely measure the rms charge radius of 6He and compare it with previous findings.
- To investigate the implications of charge radius changes on nuclear structure, particularly neutron correlations and halo formation.
Main Methods:
- Laser spectroscopy was employed on individual helium atoms cooled and confined in a magneto-optical trap.
- Isotope shifts between helium isotopes were measured.
- Precision atomic theory calculations were utilized to extract charge radii from the experimental data.
Main Results:
- The rms nuclear charge radius of 8He was determined to be 1.93(3) fm.
- The rms charge radius of 6He was measured as 2.068(11) fm, consistent with prior results.
- A significant reduction in charge radius from 6He to 8He was observed.
Conclusions:
- The observed reduction in charge radius provides evidence for altered neutron correlations in 8He.
- The results are consistent with the theoretical prediction of a neutron halo structure in 8He.
- This study advances the understanding of exotic nuclei and the forces governing them.
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