Uniqueness of the Mass-surface Relative to Iron-56

Abstract

IN practice, the mass of a neutral atom is expressed in terms of a particular nuclidic mass which is assumed to have an integral value and is termed the primary standard. With ¹²C as the primary standard (¹²₆M = 12u) nuclidic masses are found to be close to integral values and the difference between the measured mass (^A_ZM) and the integral value Au is called the ‘mass excess’¹. Alternatively, the mass of a nuclide (A, Z) relative to ¹²C could be expressed in the form: where _Z(Δ)^A₁₂ is a small proper fraction (±) which will be referred to as the ‘mass fraction’. It should be noted that the ‘mass fraction’ is a dimensionless quantity whereas the ‘mass excess’ equals _Z(Δ)^A₁₂ u.