Hyperfine Structure Constants Of Highly Excited States In Neutral And Singly Ionized Lutetium

The splitting of atomic levels caused by electron spin-orbit interactions in atoms is known as fine structure,and the atomic hyperfine structure（HFS）is the splitting of atomic levels due to the interactions between electrons and the electromagnetic multipole moments of the nucleus.The study of the HFS of atoms is gradually becoming an important research topic in the fields of astrophysics,atomic physics and nuclear physics.Compared with the fine structure,although the energy level splitting caused by HFS is much smaller order of magnitude,its effect on the atomic spectrum is not negligible.With the widespread use of a large number of high-resolution spectrometers on space telescopes and ground-based telescopes,people can distinguish many features of stellar spectra.Hyperfine splitting of atomic levels will lead to the line-broadening effect which should be carefully treated in the analysis of astrophysical spectra.If this effect is ignored,the errors in the determination of spectral line positions and equivalent widths will occur.In addition,the accurate HFS constants help to obtain information about the shape and size of the nucleus,as well as the structure and properties inside the nucleus.In recent years,there are many international research groups that perform experimental measurements and theoretical calculations of the HFS constants of neutral lutetium（Lu I）and singly ionized lutetium（Lu II）.To our knowledge,the HFS constants for 49 levels of Lu I and 20 levels of Lu II have been experimentally determined,but the HFS constants of many highly excited levels have not been measured yet.According to the NIST atomic spectroscopy database,there are 234 energy levels of Lu I and 40 energy levels of Lu II.As can be seen,there are many levels for which HFS constants have not been reported,especially for the highly excited state levels of Lu I and Lu II.In this paper,we use a self-programmed by our group HFS spectral analysis program to fit and analyze the Fourier transform spectra from the National Solar Observatory（NSO）database using the determined the HFS constants for 32 levels of Lu I from 0.00 to 43660.81 cm^-1and 10 levels of Lu II from 11796.24 to 72735.6 cm^-1,of which 25 Lu I levels and 4 Lu II levels are reported for the first time.For seven and one levels,which belong to Lu I and Lu II respectively,the measurements contain only magnetic dipole constants（A constants）,and for other levels A and B constants were simultaneously determined.Most of the estimated uncertainties are less than 10%.The experimental data obtained in this paper increase the number of levels with known HFS constants of Lu I and Lu II to 74 and 24 levels.For the levels reported in the literature,our results are in good agreement with previous experimental results,The vast majority of results differ by less than 10%.