Hyperfine structure and isotope shifts in near-infrared transitions of atomic nitrogen

Ab initiocalculations of14N and15N hyperfine structures

“…Inconsistencies appear not only in the magnitude of the parameters, but even in the relative signs of the parameters for the different J-levels arising from the same term. ‡ As discussed in [1], the hyperfine constants derived by Cangiano et al [2] for 4 P J and 4 P o J agree qualitatively with those of Jennerich et al [1]. 1 calculated for the different J-values within a given LS term with the relative weights of the different contributions making the total hyperfine constant, is obviously satisfied, by construction.…”

“…Hyperfine structure parameters are calculated for the 2p 2 ( 3 P )3s 4 P J , 2p 2 ( 3 P )3p 4 P o J and 2p 2 ( 3 P )3p 4 D o J levels, using the ab initio multiconfiguration Hartree-Fock method. The theoretical hyperfine coupling constants are in complete disagreement with the experimental values of Jennerich et al [1] deduced from the analysis of the near-infrared Doppler-free saturated absorption spectra. …”

“…Doppler-free spectra of the near-infrared N I transitions in the 2p 2 ( 3 P )3s 4 P → 2p 2 ( 3 P )3p 4 P o and 2p 2 ( 3 P )3s 4 P → 2p 2 ( 3 P )3p 4 D o multiplets have been recorded by Jennerich et al [1] using saturated absorption spectroscopy, extending the pioneer work of Cangiano et al [2] using a similar set-up. From the analysis of these spectra, Jennerich et al [1] determined the hyperfine structure constants for the various J-values of the three multiplets involved, for both isotopes 14 N and 15 N. The isotope shifts in each multiplet have also been measured, revealing a significant J-dependence of the shifts.…”

“…The strong disagreement between theory and observation [1] is really disconcerting. Hyperfine parameters have indeed been estimated ab initio successfully using similar methods for different atomic systems such as Carbon, Nitrogen, Oxygen or Sodium, as described in the introduction.…”

“…From the analysis of these spectra, Jennerich et al [1] determined the hyperfine structure constants for the various J-values of the three multiplets involved, for both isotopes 14 N and 15 N. The isotope shifts in each multiplet have also been measured, revealing a significant J-dependence of the shifts. These authors recommended a theoretical investigation of the underlying cause of this unexpected phenomenon.…”