title: The rotational spectrum of the NH+ radical in its X 2Pi and a 4Sigma- states.
abstract: 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.
authors.affiliation: Time and Frequency Division, NIST, 325 Broadway, Boulder, Colorado 80303, USA.
authors.forename: Heinz-Wilhelm
authors.initials: HW
authors.lastname: Hübers
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Evenson
authors.forename: Christian
authors.initials: C
authors.lastname: Hill
authors.forename: John M
authors.initials: JM
authors.lastname: Brown