[物理]帮忙，两道很长时间没解开的题

0219063UID: 2148658

An atom in an excited state with angular momentum quantum number J = 1 and magnetic quantum number Jz = 0 decays by electric dipole radiation to a state with total angular momentum zero. Which of the following statements is true?

(A)    No photons will be emitted along the z-axis.

(B)    Light emitted along the x-axis will be polarized along the y-axis.

(C)    The photons will be emitted isotropically.

(D)   The particles of the initial and final states are equal.

(E)    More photons will be emitted with wave vector kz > 0 than with kz < 0.

光子被辐射出来时，偏振和什么有关？



33. A proton with rest energy of approximately 1 GeV (109 electron volts) and total energy of 3 GeV interacts with another proton at rest. Which of the following could NOT be among the products of this reaction?

(A)    An antiproton.

(B)    A proton.

(C)    A pion (rest energy = 0.14 GeV).

(D)   Two pions.

(E)    A kaon (rest energy = 0.49 GeV).

beckhamwiseUID: 142845

第一题选A，因为光子角动量只可能在XY平面，所以在z方向不能观察到
第二题选E，如果该反应成立，则奇异数不守恒，而没有轻子参与作用，所以不是弱相互作用