(6212) Hydrogen atom in magnetic field, probed by electric field

Consider an Hydrogen atom that is placed in a constant homogeneous magnetic field \( \mathcal{B} \) that points in the Z direction. An electric field \( \mathcal{E} \) is turned on. The interaction term is \( V = - e\mathcal{E} \cdot r \) . The spin of the electron can be ignored.

(1) Calculate the matrix elements of \( V \) in the standard basis for \( \mathcal{E} \) that points in the Z direction.

(2) Calculate the matrix elements of \( V \) in the standard basis for \( \mathcal{E} \) that points in the X direction.

(3) Repeat the derivation in the latter case using coordinates such that \( \mathcal{B} \) points in the X direction, and \( \mathcal{E} \) in the Z direction.

(4) Explain what are the selection rules of transitions in the following cases:
\( \mathcal{E} = (0,0,\cos(\Omega t)) \)
\( \mathcal{E} = (\cos(\Omega t),0,0) \)
\( \mathcal{E} = (\cos(\Omega t),\sin(\Omega t),0) \)
Assume that \( \Omega \) is comparable to the Zeeman splitting.