Study Of Hyperfine Structure Constants Of Neutral Praseodymium

In atoms,the small splitting of energy levels and spectral lines caused by the coupling between the nuclear and electronic magnetic moments is called the hyperfine structure（HFS）splitting of atoms.The study of atomic HFS is of great significance in many fields such as atomic physics,nuclear physics and astrophysics.Based on the atomic HFS,one can understand and apply the structure and spectral properties of the atoms more completely,as well as determine the nuclear moment and the shape of the nucleus.In astrophysics,the resolution of celestial spectra has been improved greatly due to the advancement of astronomical observation technology.In order to extract more information from these high-resolution spectra,atomic data are crucial,which includes HFS data.The HFS splitting of levels appears as broadening,shifting and modification of the shape of an observed line.It could lead to an erroneous analysis of the celestial spectra if these effects are not taken into account.In addition,HFS also plays an important role in the diagnosis of the microstructure of solid materials.Since the 20th century,the study of atomic HFS has been gradually started,especially for rare earth elements.Praseodymium（Pr）is a rare earth element,and Pr atom（Pr I）and the lower valence ions are one of the most abundant systems of all chemical elements in terms of spectral lines.Since Pr I has a large number of energy levels and spectral lines,and the spectral lines of Pr I have been observed in many stars,especially chemically peculiar（CP）stars,it is of great significance to measure the HFS of Pr I levels.Over the years,many groups had investigated the HFS in Pr I using different methods.To the best of our knowledge,369 HFS constants of Pr I levels have been determined so far.However,for the 429 Pr I levels known in the National Institute of Standards and Technology（NIST）atomic spectroscopy database,there are still many HFS of Pr I levels that need to be investigated.In this paper,the Fourier transform spectra（FTS）of praseodymium were obtained from the National Solar Observatory（NSO）database（https://nso.edu/data/historical-archive/）,and a large number of spectral lines of Pr I in the obtained 11 FTS were analyzed using a spectral analysis fitting procedure written according to the least squares method and HFS theory.The values of the magnetic dipole HFS constants A were determined for 56 levels of Pr I from 0 to 27602.42 cm^-1,and most of the results were within 10%error.The results obtained in this paper supplement the HFS data of Pr I,enrich the atomic spectral database,and contribute to the study of the atomic structure of Pr and the accurate analysis of the celestial spectra,which has important reference value in the fields of atomic physics,nuclear physics,plasma physics and astrophysics.