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The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of LiI7 to determine the nuclear hexadecapole interaction of the iodine nucleus. The nuclear magnetic octupole interaction was also considered but found to be marginally significant. A total of 172 transitions in vibrational states 0-3 and rotational states 1-6 have been included in a fit to determine the iodine nuclear quadrupole, spin-rotation, and hexadecapole interactions, the lithium quadrupole and spin-rotation interactions, and the tensor and scalar parts of the spin-spin interaction. Vibration and rotation dependencies of these constants have been determined. The results include: eHh=−0.0151(30), eQIqI=−194351.212(17)−8279.521(46)(v+1/2)+100.616(34)(v+1/2)2−0.3949(73)(v+1/2)3−6.41977(50)J(J+1)+0.10593(33)(v+1/2)J(J+1),eQLiqLi=172.613(52)−3.26(14)(v+1/2)+0.00145(87)J(J+1),cI=6.80260(32)+0.00303(49)(v+1/2)−0.000118(13)J(J+1), cLi=0.75872(72)−0.0088(11)(v+1/2), c3=0.62834(68)−0.0050(11)(v+1/2), c4=0.06223(36)+0.00041(26)(v+1/2), and eΩIωI′=0.000112(73), all in kHz with one standard deviation uncertainties for the last 2 digits in ( ).

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The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of CsF to determine the nuclear quadrupole interaction of the cesium nucleus. A total of 95 transitions in vibrational states vϭ0Ϫ5 and rotational states Jϭ1Ϫ8 have been included in a fit to determine the cesium nuclear quadrupole and spin-rotation interactions, the fluorine spin-rotation interaction, and the tensor and scalar parts of the spin-spin interaction. Vibration and rotation dependencies of these constants have been determined, allowing correction for zero point vibration effects. This experimental Cs nuclear quadrupole coupling constant when combined with the electric field gradient calculated using a relativistic coupled cluster method yields a nuclear quadrupole moment of the Cs nucleus equal to eQϭϪ3.43098 mbarn. The vibrational dependence of the coupling constant is smaller than the theoretical estimate. The coupling constants we have determined are the following: eQ Cs q Cs ϭ1245.598(10)Ϫ14.322(25)(vϩ1/2)ϩ0.080(14) ϫ(vϩ1/2) 2 ϩ0.0040(22)(vϩ1/2) 3 Ϫ0.00209(59)J(Jϩ1)ϩ0.00048(40)(vϩ1/2)J(Jϩ1), c Cs ϭ0.66177(14)Ϫ0.01509(28)(vϩ1/2)ϩ0.000550(94)(vϩ1/2) 2 , c F ϭ15.08163(84)Ϫ0.1744(14) ϫ(vϩ1/2)ϩ0.00234(41)(vϩ1/2) 2 Ϫ0.000093(13)J(Jϩ1), c 3 ϭ0.92713(53)Ϫ0.00917(93)(v ϩ1/2)ϩ0.00097(29)(vϩ1/2) 2 , c 4 ϭ0.62745(30)Ϫ0.00903(22)(vϩ1/2). All values are in kHz units, with one standard deviation uncertainty estimates in the last two digits shown in ().

A high-precision examination of the hyperfine spectrum of 6LiI in comparison with 7LiI shows a shift in the iodine nuclear electric quadrupole moment that cannot be accounted for by a model in which the electric field gradient at the iodine site is assumed to depend only upon the internuclear distance between Li and I. The other hyperfine interactions are consistent between the two isotopomers, including the previously reported electric hexadecapole interaction of the iodine nucleus.

The molecular beam electric resonance technique has been used to examine the hyperfine spectrum of RbF. The Rb nuclear electric quadrupole interaction, the spin-rotation interactions, and tensor and scalar spin-spin interactions have been measured for both Rb isotopes, including their dependence on vibrational and rotational states. Transition frequencies have been determined to a precision of better than 1 Hz in many cases. The magnetic interactions in the two isotopomers are consistent with what is expected from the known masses and magnetic dipole moments. In the case of the Rb nuclear electric quadrupole interaction, adjustments have been made for a small isotopomer shift, and for the ratio of the effective nuclear electric quadrupole moments, Q(87Rb)Q(85Rb) = 0.483 830 1+/-0.000 001 8. The effective quadrupole interaction includes a pseudoquadrupole interaction that may be significant at this level of precision, but cannot be distinguished experimentally.

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The molecular beam electric resonance technique has been used to conduct a high precision examination of the hyperfine spectrum of the four isotopomers of RbCl. Coupling constants for the nuclear electric quadrupole interactions, the spin-rotation interactions, the tensor and scalar spin-spin interactions, and a rubidium nuclear octupole interaction, and their dependence on vibrational and rotational states have been determined. The dominant interaction, the rubidium nuclear electric quadrupole interaction, shows a small shift with substitution of the chlorine isotope.