Isotopes of copper

Both stable isotopes of copper (⁶³Cu and ⁶⁵Cu) 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 offers a relatively large number of radioisotopes that are potentially useful for nuclear medicine.

There is growing interest in the use of ⁶⁴Cu, ⁶²Cu, ⁶¹Cu, and ⁶⁰Cu for diagnostic purposes and ⁶⁷Cu and ⁶⁴Cu for targeted radiotherapy. For example, ⁶⁴Cu has a longer half-life than most positron-emitters (12.7 hours) and is thus ideal for diagnostic PET imaging of biological molecules.

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(6) s and 1.27(3) 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. (There is also a significant β⁻n decay mode to ⁷⁵Zn.) 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(25) 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. (2025) found that both the ground state and the isomer have similar half-lives around 656(2) 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.