title: Quadrupole splittings in the near-infrared spectrum of14NH3.
abstract: Sub-Doppler, saturation dip, spectra of lines in the v1+ v3, v1+ 2v4, and v3+ 2v4bands of14NH3have been measured by frequency comb-referenced diode laser absorption spectroscopy. The observed spectral line widths are dominated by transit time broadening and show resolved or partially-resolved hyperfine splittings that are primarily determined by the14N quadrupole coupling. Modeling of the observed line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the excited state level has hyperfine splittings similar to the same rotational level in the ground state. The data provide accurate frequencies for the line positions and easily separate lines overlapped in Doppler-limited spectra. The observed hyperfine splittings can be used to make and confirm rotational assignments and ground state combination differences obtained from the measured frequencies are comparable in accuracy to those obtained from conventional microwave spectroscopy. Several of the measured transitions do not show the quadrupole hyperfine splittings expected based on their existing rotational assignments. Either the assignments are incorrect or the upper levels involved are perturbed in a way that affects the nuclear hyperfine structure.
authors: Division of Chemistry, Department of Energy and Photon Sciences, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
authors: Sylvestre
authors: S
authors: Twagirayezu
authors: Division of Chemistry, Department of Energy and Photon Sciences, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
authors: Gregory E
authors: GE
authors: Hall
authors: Division of Chemistry, Department of Energy and Photon Sciences, Brookhaven National Laboratory, Upton, New York 11973-5000, USA.
authors: Trevor J
authors: TJ
authors: Sears