An –particle ( ) collides with a stationary nucleus in the laboratory and the…

PHYSICS · Subjective · A Level · Physics · Nuclear physics · Nuclear physics

Problem

An α\alpha–particle ( 24He_2^4\text{He} ) collides with a stationary  23He\,_2^3\text{He} nucleus in the laboratory and the following reaction is attempted: 24He+ 23He  ⟶  36Li+p_2^4\text{He}+\,_2^3\text{He}\;\longrightarrow\;_3^6\text{Li}+ p Atomic masses are: m(24He)=4.002603 u m(_2^4\text{He}) = 4.002603\,\text u, m(23He)=3.016029 u m(_2^3\text{He}) = 3.016029\,\text u, m(36Li)=6.015122 u m(_3^6\text{Li}) = 6.015122\,\text u, m(p)=1.007276 u m(p) = 1.007276\,\text u. Use 1 u=931.5 MeV/c21\,\text u = 931.5\,\text{MeV}/c^{2}. (a) Compute the Q–value of the reaction. (b) Show that the reaction is endothermic. (c) Determine the minimum kinetic energy (threshold energy) that the incident α\alpha–particle must possess for the reaction to take place when the  23He\,_2^3\text{He} target is at rest. Express the answer in MeV.

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