Ab initiocalculations of¹⁴N and¹⁵N hyperfine structures

Abstract

Abstract. 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.

Relativistic effects on the hyperfine structures of2p4(3P)3p2Do,<

“…On the other hand, ab initio calculations of hyperfine constants for 14 N and 15 N [14] were found to be in complete disagreement with the experimental values of Jennerich et al [15], also deduced from the analysis of the near-infrared Doppler-free saturated absorption spectra. This nitrogen theory-observation discrepancy problem was recently solved through a reinterpretation of the recorded weak spectral lines as crossover signals [16], leading to a new set of experimental hyperfine constants in very good agreement with the ab initio predictions [14].…”

“…On the other hand, ab initio calculations of hyperfine constants for 14 N and 15 N [14] were found to be in complete disagreement with the experimental values of Jennerich et al [15], also deduced from the analysis of the near-infrared Doppler-free saturated absorption spectra. This nitrogen theory-observation discrepancy problem was recently solved through a reinterpretation of the recorded weak spectral lines as crossover signals [16], leading to a new set of experimental hyperfine constants in very good agreement with the ab initio predictions [14]. Considering that the apparition of crossover signals in Doppler-free saturated absorption spectroscopy that has been used for both fluorine [3] and nitrogen [15], is helpful in some cases but also problematic in others, we investigate in the present work the relativistic corrections that could explain the non relativistic theory-observation discrepancy mentioned above for the A 5/2 -value of 2p…”

“…The hyperfine constant A J is estimated from the expectation value of this operator, using (14) and the atomic state function (5).…”

“…For the latter, we use the above reduction strategy, adopting the reversed orbital order consisting in coupling sequentially the subshells by decreasing n and l. This technique indeed reduces substancially the size of the MCHF expansions while keeping the dominant correlation contributions [14]. For specifying the AS, it is sometimes more convenient to use another notation involving curly brackets instead of brackets, where the number of orbitals for each angular symmetry is specified, i.e.…”

From atoms to biomolecules: a fruitful perspective

“…The evaluation of the hyperfine constants and their comparison with observation brings sometimes surprises. For hyperfine structures of 15 N and 14 N spectral lines observed in the near-infrared [85], we estimated ab initio hyperfine constants [91] that disagree completely with the experimental parameters obtained by fitting the observed hyperfine spectra [85]. We proposed a new interpretation of the recorded weak spectral lines [21] as crossover signals, producing a new set of experimental hyperfine constants in very good agreement with the ab initio predictions.…”