Magnetic dipole transitions in the hydrogen molecule

In homonuclear molecules, such as ${\mathrm{H}}_2$, the electric dipole transitions are strongly forbidden, and the transitions between rovibrational states are of the electric quadrupole type. We show, however, that magnetic dipole transitions also take place, although they are significantly weaker. We evaluate the probabilities of such transitions between several of the lowest rotational states and compare them with those of the corresponding electric quadrupole transitions.

Figure 1

Comparison of the rates of the magnetic dipole transition ($M1$) with the $\Delta J=0$ electric quadrupole transition ($E2$) in ${\mathrm{H}}_2$.