The GATE Grind

GATE 2025 PH – Question 48

Nuclear and Particle Physics · alpha decay, beta-decay, electromagnetic transitions in nuclei · 2 marks · Multiple select

Consider two hypothetical nuclei X1 and X2 undergoing β decay, resulting in nuclei Y1 and Y2, respectively. The decay scheme and the corresponding JP values of the nuclei are given in the figure. Which of the following option(s) is/are correct? (J is the total angular momentum and P is parity)

Beta decay schemes with spin and parity labels.
  1. X1 →Y1 is Fermi transition and X2 →Y2 is Fermi transition
  2. X1 →Y1 is Fermi transition and X2 →Y2 is Gamow-Teller transition
  3. X1 →Y1 is Gamow-Teller transition and X2 →Y2 is Fermi transition
  4. X1 →Y1 is Gamow-Teller transition and X2 →Y2 is Gamow-Teller transition

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Correct answer: (B) X1 →Y1 is Fermi transition and X2 →Y2 is Gamow-Teller transition

Explanation

Allowed Fermi decay has delta J zero and includes 0-to-0. Gamow–Teller allows delta J one and excludes 0-to-0. Thus the two shown transitions are Fermi and Gamow–Teller.