ɪt dᵻkˈeɪz baɪ ˌaɪsoʊmˈɛɹɪk tɹænsˈɪʃən wɪð ɐ hˈæflˈaɪf ʌv tˈuːhˈʌndɹɪd fˈoːɹɾi wˈʌn jˈɪɹz, wˌɪtʃ mˌeɪks ɪɾ ʌnjˈuːʒuːəl, bˈoʊθ fɔːɹ ɪts lˈɔŋ hˈæflˈaɪf fɚɹən ˈaɪsəmɚ, ænd ðæt sˈɛd hˈæflˈaɪf ɡɹˈeɪtli ɛksˈiːdz ðæt ʌvðə ɡɹˈaʊnd stˈeɪt ʌvðə sˈeɪm ˈaɪsətˌoʊp.
It decays by isomeric transition with a half-life of 241 years, which makes it unusual, both for its long half-life for an isomer, and that said half-life greatly exceeds that of the ground state of the same isotope.