Scientific Program at RIKEN-RAL Port 4
When a negative muon is captured by an atom, they form a muonic atom, in which an electron in the atom is replaced by a muon.
Since muon's mass is about 200 times larger than that of electron, the radius of orbits for muon is 200 times smaller.
This makes the energies of photons emitted when the muon goes through series of transition towards its ground level very sensitive to the size of nucleus, or its charge radius.
This method has been applied to many stable nuclei to measure its sizes for many years.
Now in Port 4, a novel techinique is being developped to apply this method to unstable nuclei.
The idea is to use solid hydrogen/deutrium layer as a bed for unstable nucleus
and negative muons.
Ions of unstable nuclei are implanted to the hydrogen/deutrium layer.
Negative muons are injected to the target, decelerated in the larer, forming
muonic deutrium.
Then negative muon transfers to a heavier atom forming a muonic atom with
unstable nuclei.
Currently feasibility studies for this technique are carried out using stable
ion beam.
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