What kind of nuclear reaction is seen in 146/62 sm -> 142/60 nd + 4/2 he?

Answer is an alpha emission

Alpha decay is an emission of ₂⁴He nucleus. If an element undergoes an alpha decay, the mass of the daughter nucleus formed is reduced by 4 compared to mass of parent atom and atomic number is reduced by 2 compared to atomic number of parent atom.

Here parent atom is Sm which has atomic number as 62 and mass number as 146. Since the emitted particle is a ₂⁴He nucleus this is an alpha decay. Daughter atom will have 146 - 4 = 142 as mass number and 62 - 2 = 60 as atomic number. Hence, daughter atom should be Nd which has atomic number as 60.