A proton-rich neutral atom can undergo β⁺-decay. Its atomic mass exceeds that of the neutral daughter atom by 0.0015 u. Take mₑc² = 0.511 MeV and 1 u·c² = 931.5 MeV. The Q-value of the β⁺-decay is closest to:
Options

Question

A proton-rich neutral atom can undergo β⁺-decay. Its atomic mass exceeds that of the neutral daughter atom by 0.0015 u. Take mₑc² = 0.511 MeV and 1 u·c² = 931.5 MeV. The Q-value of the β⁺-decay is closest to:

Options

G1 Physics · Accepted Answer

For β⁺-decay using neutral atomic masses, two electron rest masses must be subtracted: Q = [M(parent)−M(daughter)]c² − 2mₑc². Mass-energy difference: 0.0015×931.5 = 1.39725 MeV. Positron-production correction: 2mₑc² = 2×0.511 = 1.022 MeV. Therefore, Q = 1.39725−1.022 = 0.37525 MeV. Hence Q ≈ 0.375 MeV. Correct option: A.