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In physics, mirror nuclei are a pair of isobars of two different elements where the number of protons of isobar one (Z1) equals the number of neutrons of isobar two (N2) and the number of protons of isotope two (Z2) equals the number of neutrons in isotope one (N1); in short: Z1 = N2 and Z2 = N1. This implies that the mass numbers of the isotopes are the same: N1 + Z1 = N2 + Z2.
Examples of mirror nuclei include:
| Isobar 1 | Z1 | N1 | Isobar 2 | Z2 | N2 |
|---|---|---|---|---|---|
| 3H | 1 | 2 | 3He | 2 | 1 |
| 14C | 6 | 8 | 14O | 8 | 6 |
| 15N | 7 | 8 | 15O | 8 | 7 |
| 24Na | 11 | 13 | 24Al | 13 | 11 |
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 by a neutron. 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.[1][2]
In 2020 strontium-73 and bromine-73 were found to not behave as expected.[3] The ground state of 73
35Br
has spin and parity 1/2−, whereas the ground state of 73
38Sr
was inferred to have spin and parity 5/2−, matching a low-lying 27 keV excited state of 73
35Br
.[4]
References
edit- ^ Cottle, P. D. (2002-04-12). "Excitations in the Mirror Nuclei 32Ar and 32Si". Physical Review Letters. 88 (17): 172502. Bibcode:2002PhRvL..88q2502C. doi:10.1103/PhysRevLett.88.172502. PMID 12005747. Retrieved 2018-01-08.
- ^ Kamat, Sharmila (2002-04-23). "Focus: Gazing into a Nuclear Mirror". Physics. 9. American Physical Society. Retrieved 2016-04-11.
- ^ Discovery by UMass Lowell-led team challenges nuclear theory
- ^ Hoff, D. E. M.; Rogers, A. M.; Wang, S. M.; Bender, P. C.; Brandenburg, K.; Childers, K.; Clark, J. A.; Dombos, A. C.; Doucet, E. R.; Jin, S.; Lewis, R.; Liddick, S. N.; Lister, C. J.; Meisel, Z.; Morse, C.; Nazarewicz, W.; Schatz, H.; Schmidt, K.; Soltesz, D.; Subedi, S. K.; Waniganeththi, S. (1 April 2020). "Mirror-symmetry violation in bound nuclear ground states". Nature. 580 (7801): 52–55. doi:10.1038/s41586-020-2123-1.