Isotopes of neodymium

Naturally occurring neodymium (₆₀Nd) is composed of five stable isotopes, ¹⁴²Nd, ¹⁴³Nd, ¹⁴⁵Nd, ¹⁴⁶Nd and ¹⁴⁸Nd, with ¹⁴²Nd being the most abundant (27.2% natural abundance), and two long-lived radioisotopes, ¹⁴⁴Nd and ¹⁵⁰Nd. In all, 35 radioisotopes of neodymium have been characterized up to now, with the most stable being naturally occurring isotopes ¹⁴⁴Nd (alpha decay, a half-life (t_1/2) of 2.29×10¹⁵ years) and ¹⁵⁰Nd (double beta decay, t_1/2 of 9.3×10¹⁸ years), and for practical purposes they can be considered to be stable as well. All of the remaining radioactive isotopes have half-lives that are less than 11 days, and the majority of these have half-lives that are less than 70 seconds; the most stable artificial isotope is ¹⁴⁷Nd with a half-life of 10.98 days. This element also has 15 known meta states with the most stable being ^139mNd (t_1/2 5.5 hours), ^135mNd (t_1/2 5.5 minutes) and ^133m1Nd (t_1/2 ~70 seconds).

The primary decay modes for isotopes lighter than the most abundant stable isotope (also the only theoretically stable isotope), ¹⁴²Nd, are electron capture and positron decay, and the primary mode for heavier radioisotopes is beta decay. The primary decay products for lighter radioisotopes are praseodymium isotopes and the primary products for heavier ones are promethium isotopes.