Measurement of the Sequential 3α Process in the Photodissociation of ¹²C

The cross sections for the ¹²C(γ,α)⁸Be→ 3α reaction have been successfully measured using exclusive coincidence between three α particles, minimizing Compton background. Sequential breakup kinematics are evident, and the cross sections are presented as locally averaged histogram values. Theoretical {Fresco} CDCC-CRC calculations reproduce the experimental data, showing that the process involves electromagnetic coupling to both ⁸Be0⁺ and ⁸Be2⁺ states. This study confirms that the ¹²C(γ,α)⁸Be→ 3α reaction proceeds via a sequential mechanism, crucial for understanding its significance in radiotherapy dosimetry.