# Uranium isotopes with m in superscript

• I
Gold Member
On the page https://en.wikipedia.org/wiki/Isotopes_of_uranium, some of the superscripts have, besides the atomic number, also an "m". For example, besides the usual isotope 234U with spin 0+, there is also the isotope 234mU (with nuclear spin 6-). What is this "m"?

While I am at it, what is the "+" next to the 0? +0 = -0, no? (It can't be the charge, given the "6-" for the other one.)

m is abbreviation for "metastable". This signifies "nuclear isomers" - nuclear states which have higher energy than some other state of same neutron and proton number and relatively long half-life.

Gold Member
thank you very much, snorkack. That completely answers the first question.

mfb
Mentor
While I am at it, what is the "+" next to the 0? +0 = -0, no? (It can't be the charge, given the "6-" for the other one.)
It is the parity. It is not a sign for the spin.