Isotopes of copper

has two stable isotopes, ⁶³Cu and ⁶⁵Cu, along with 28 known radioisotopes from ⁵⁵Cu to ⁸⁴Cu. The most stable radioisotope, ⁶⁷Cu, has a half-life of only 61.83 hours, then follow ⁶⁴Cu at 12.70 hours and ⁶¹Cu at 3.34 hours. The others have half-lives all under an hour and most under a minute. The isotopes with mass below 63 generally undergo positron emission and electron capture to nickel isotopes, while isotopes with mass above 65 generally undergo β⁻ decay to zinc isotopes. The single example in between, ⁶⁴Cu, decays both ways.
There are at least 10 metastable isomers of copper, of which the most stable is ^68mCu with a half-life of 3.75 minutes.

List of isotopes

Copper nuclear magnetic resonance

Both stable isotopes of copper have nuclear spin of 3/2−, and thus produce nuclear magnetic resonance spectra, although the spectral lines are broad due to quadrupolar broadening. ⁶³Cu is the more sensitive nucleus while ⁶⁵Cu yields very slightly narrower signals. Usually though ⁶³Cu NMR is preferred.

Copper-64 and other potential medical isotopes

Copper offers a relatively large number of radioisotopes that are potentially useful for nuclear medicine.
There is growing interest in the use of Cu, Cu, Cu, and Cu for diagnostic purposes and Cu and Cu for targeted radiotherapy. For example, Cu has a longer half-life than most positron-emitters and is thus ideal for diagnostic PET imaging of biological molecules.

Copper-76

Copper-76 is a radioactive istope of copper with one long-lived isomer copper-76m, whose half-lives are disputed. A 1990 study by Winger et al. at KEK reported two long-lived states with half-lives of 0.57 s and 1.27 s, with the longer-lived state being the isomer and having lower spin. Subsequent experiments could not identify the claimed long-lived isomer, with the isomer that was observed later being assigned a spin of 3− based on the levels of ⁷⁶Zn populated by β⁻ decay. However, a 2024 experiment at the University of Jyväskylä discovered that the previously observed 3− state is actually the isomer, whose excitation energy is 64.8 keV, and the long-lived ground state probably has spin 1+; Canete et al. claim that there is a significant isomeric transition to the ground state. However, Olaizola et al. found that both the ground state and the isomer have similar half-lives around 656 ms, like was found in most previous experiments. Additionally, they find that the non-3− state is probably 6− based on shell model calculations, excluding a significant isomeric transition and preventing identification of the ground state.