The rotational spectrum of the NH+ radical in its X 2Pi and a 4Sigma- states.

Transitions between the spin-rotational levels of the (14)NH(+) radical in the v = 0 levels of its X (2)Pi and a (4)Sigma(-) states have been studied by the technique of laser magnetic resonance at far-infrared wavelengths. The data have been combined with a previous zero-field measurement of the J = 1 1/2 - 1/2 transition frequencies at 1.01 THz to determine a much improved set of molecular parameters for NH(+) in the X (2)Pi state; the major parameters for the a (4)Sigma(-) state have also been determined. A full determination of the hyperfine parameters for both (14)N and (1)H nuclei has been achieved for the first time. Accurate predictions of the transition frequencies between the low-lying levels of the radical in the absence of a magnetic field have also been made, including lambda-doubling frequencies for use by radio astronomers.

The rotational and fine-structure spectrum of FeH, studied by far-infrared laser magnetic resonance.

Transitions between the spin-rotational levels of the FeH radical in the upsilon=0 level of the X (4)Delta ground state have been detected by the technique of laser magnetic resonance at far-infrared wavelengths. Both pure rotational and fine-structure transitions have been observed; lambda-type doubling is resolved on all the observed transitions. The energy levels of FeH are strongly affected by the breakdown of the Born-Oppenheimer approximation and cannot be modeled accurately by an effective Hamiltonian. The data are therefore fitted to an empirical formula to yield term values and g factors for the various spin-rotational levels involved. Many of the resonances show a doubling that arises from the proton hyperfine structure. These splittings are analyzed in a similar manner.