# Selection Rules (Time Dependent Perturbation Theory)

Diracobama2181
Homework Statement:
Suppose that the system is a single spinless particle of mass $$M$$ and charge $$e$$ in a central Coulomb potential and the quantum numbers of the initial state are labeled $$|n, l, m>$$ in the usual way. It is subject to perturbation with magnetic field $$B(t) = B_0e ^{−λt}$$ pointing in the x direction, which adds a term $$eL_xB(t)/(2Mc)$$ to the Hamiltonian. Find the quantum number selection rules for allowed transitions to a different state.
Relevant Equations:
$$[L_x,X]=0$$
I suppose my question is, since X commutes for H, does this mean that the selection rules are $$<n',l',m'|X|n,l,m>=0$$ unless $$l'=l\pm 1$$ and $$m'=m\pm 1$$, as specified in Shankar?