The Radiofrequency Spectrum ofRb85F andRb87F by the Electric Resonance Method

Abstract

The radiofrequency spectrum of the two molecular species ${\mathrm{Rb}}^{85}$F and ${\mathrm{Rb}}^{87}$F was studied by the molecular beam electric resonance method. The electrical quadrupole interaction constant, $\frac{e{q}_1{Q}_1}{h}$, of Rb in RbF was determined for ${\mathrm{Rb}}^{87}$F in rotational states $J=1\mathrm{}$ and $J=2\mathrm{}$ for the first few vibrational states, and for ${\mathrm{Rb}}^{85}$F in rotational state $J=1\mathrm{}$ for the first few vibrational states. The interaction constants are unusually large for an alkali halide molecule; for the zeroth vibrational state of ${\mathrm{Rb}}^{85}$F, $\frac{e{q}_1{Q}_1}{h}=-70.31\mathrm{}\pm 0.10$ Mc/sec. and for the zeroth vibrational state of ${\mathrm{Rb}}^{87}$F, $\frac{e{q}_1{Q}_1}{h}=-34.00\mathrm{}\pm 0.06$ Mc/sec. The absolute value of the interaction constant decreases about 1.1 percent from one vibrational state to the next higher one; the values of the interaction constants for rotational states $J=1\mathrm{}$ and $J=2\mathrm{}$ are the same within the limit of error. The ratio of the electric quadrupole moment of ${\mathrm{Rb}}^{85}$ to that of ${\mathrm{Rb}}^{87}$ is +2.07±0.01. Results are reported on the spin-orbit coupling $c_2\left({\mathbf{I}}_2·\mathbf{J}\right)$, between the spin of the fluorine nucleus and the molecular rotational angular momentum. For the zeroth vibrational state of ${\mathrm{Rb}}^{85}$F, $\left|\frac{c_2}{h}\right|=11\mathrm{}\pm 3$ kc/sec. and for the zeroth vibrational state of ${\mathrm{Rb}}^{87}$F, $\left|\frac{c_2}{h}\right|=14\mathrm{}\pm 4$ kc/sec. No variation in $\left|\frac{c_2}{h}\right|$, with vibrational state was observed. Finally, an unpredicted line group was observed in the spectrum at one-half the frequency of one of the line groups in the ${\mathrm{Rb}}^{85}$F spectrum. Possible origins of this line group are discussed, including that of a double quantum transition. The vibrational frequency, ${\omega }_0$, of

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