The size of the lightest halo nucleus
DOI: 10.1063/1.4797199
The size of the lightest halo nucleus, helium-6, has been precisely measured by performing laser spectroscopy on individually trapped 6He atoms. Although one neutron does not stick to an alpha particle, two neutrons can, and for about a second, they form the loosely bound halo of the 6He nucleus. The size of this exotic nucleus reveals the fundamental forces among the constituent nucleons. Physicists at Argonne National Laboratory produced 6He atoms at the lab’s ATLAS accelerator facility and quickly captured and cooled them with a magneto-optical trap. By comparing spectra of 6He with 4He, the scientists determined that the charge radius of the 6He nucleus was just over 2 fm. The result is model independent and is precise enough to test the available theoretical predictions. (
