In
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
, mirror nuclei are a pair of
isobars of two different
elements where the number of protons of isobar one (Z
1) equals the number of neutrons of isobar two (N
2) and the number of protons of isotope two (Z
2) equals the number of neutrons in isotope one (N
1); in short: Z
1 = N
2 and Z
2 = N
1. This implies that the mass numbers of the isotopes are the same: N
1 + Z
1 = N
2 + Z
2.
Examples of mirror nuclei include:
Pairs of mirror nuclei have the same spin and parity. If we constrain to odd number of nucleons (A=Z+N) then we find mirror nuclei that differ from one another by exchanging a
proton
A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...
by a
neutron
The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...
. Interesting to observe is their binding energy which is mainly due to the strong interaction and also due to
Coulomb interaction. Since the strong interaction is invariant to protons and neutrons one can expect these mirror nuclei to have very similar
binding energies.
In 2020 strontium-73 and bromine-73 were found to not behave as expected. The ground state of has
spin and
parity 1/2−, whereas the ground state of was inferred to have spin and parity 5/2−, matching a low-lying 27 keV excited state of .
References
{{DEFAULTSORT:Mirror Nuclei
Nuclear physics