The above cascade of (n,γ) reactions produces a mixture of different curium isotopes. Their post-synthesis separation is cumbersome, and therefore a selective synthesis is desired. Curium-248 is favored for research purposes because of its long half-life. The most efficient preparation method of this isotope is via α-decay of the californium isotope 252Cf, which is available in relatively large quantities due to its long half-life (2.65 years). About 35–50 mg of 248Cm is being produced by this method every year. The associated reaction produces 248Cm with isotopic purity of 97%.