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: $eqQ=e\overline{q}Q+e{q}^{\mathrm{}\left(J\right)\mathrm{}}\mathrm{QJ}(J+1\mathrm{})+e{q}^{\mathrm{}\left(v\right)\mathrm{}}\mathrm{Qv}.\mathrm{}$

The results for ${\mathrm{Rb}}^{87}$ in ${\mathrm{Rb}}^{87}$F are: $\frac{\left|e\overline{q}Q\right|}{h}=33.96\mathrm{}\pm 0.02$ Mc, $\frac{\left|e{q}^{\mathrm{}\left(v\right)\mathrm{}}Q\right|}{h}=410\mathrm{}\pm 40$ kc, $\frac{\left|e{q}^{\mathrm{}\left(J\right)\mathrm{}}Q\right|}{h}=26\mathrm{}\pm 4$ cycles/sec, $\frac{\left|c_a\right|}{h}=1.1\mathrm{}\pm 0.1$ kc. $e{q}^{\mathrm{}\left(v\right)\mathrm{}}Q$ and $e{q}^{\mathrm{}\left(J\right)\mathrm{}}Q$ are shown to have signs opposite to that of $e\overline{q}Q$.

The results for ${\mathrm{Rb}}^{87}$ in ${\mathrm{Rb}}^{87}$Cl are: $\frac{\left|e\overline{q}Q\right|}{h}=25.37\mathrm{}\pm 0.04$ Mc, $\frac{\left|e{q}^{\mathrm{}\left(v\right)\mathrm{}}Q\right|}{h}=230\mathrm{}\pm 50$ kc, $\frac{\left|e{q}^{\mathrm{}\left(J\right)\mathrm{}}Q\right|}{h}=12\mathrm{}\pm 2$ cycles/sec, $\frac{\left|c_a\right|}{h}=1.0\mathrm{}\pm 0.1$ kc. $e{q}^{\mathrm{}\left(v\right)\mathrm{}}Q$ and $e{q}^{\mathrm{}\left(J\right)\mathrm{}}Q$ are shown to have signs opposite to that of $e\overline{q}Q$.

• Received 17 October 1951

DOI:https://doi.org/10.1103/PhysRev.85.799