Molecular Beam Magnetic Resonance Spectra ofRb87F andRb87Cl at Zero Field

The radiofrequency spectra of ${\mathrm{Rb}}^{87}$F and ${\mathrm{Rb}}^{87}$Cl were investigated by the zero field molecular beam magnetic resonance method. The quadrupole line was found to be split into a series of component lines. The separations between the lines, as well as the shapes of the lines, are explained by taking into account the effects of (1) a cosine coupling of the form $c_a\mathbf{I}·\mathbf{J}$ between the spin of ${\mathrm{Rb}}^{87}$, ${\mathbf{I}}_a$, and the rotational angular momentum of the molecule J; and (2) the dependence of the quadrupole interaction constant $\mathrm{eqQ}$ on vibrational quantum number $v$ and rotational quantum number $J$ of the form: $eqQ=e\overline{q}Q+e{q}^{\mathrm{}\left(J\right)\mathrm{}}\mathrm{QJ}(J+1\mathrm{})+e{q}^{\mathrm{}\left(v\right)\mathrm{}}\mathrm{Qv}.\mathrm{}$