Measurement Studies On Hyperfine Structures And Natural Radiative Lifetimes Of Ga? And Sc? Levels

Hyperfine interactions and transition dynamics characteristic of atoms are the area of research that has been a widespread concern. Precise measurements of the hyperfine interactions play an essential role in providing detailed and valuable information on the shape and size of nuclear and electronic correlations, testing the accuracy of wave functions of atoms, and gaining a deep insight into the atomic structure. Accurate radiative parameters can provide valuable information on atomic transitions, reveal electromagnetic radiation characteristic. In astrophysics, accurate hyperfine structure(HFS) constants are indispensable atomic data for the absorption line profiles modeled process in stellar spectral analyses. Radiative parameters of atoms such as natural radiative lifetimes, branching fractions, and oscillator strengths(transition probabilities) are essential for the investigation of the astrophysics.In recent years, with the rapid development of astronomical observational technique, a large number of high resolution and signal-to-noise ratio astronomical spectral were observed. These high resolution solar and stellar spectra reveal hyperfine structures of many spectral lines, the accurate analysis of these spectra need more and more reliable atomic data such as HFS constants, natural radiative lifetimes,branching fractions and oscillator strengths. This paper focus on the HFS and natural radiative lifetimes measurements of Ga?(Z = 31) and Sc?(Z = 21) and obtain lots of reliable results.HFS constants and radiative lifetimes of Rydberg levels of Ga? and radiative lifetimes of some high-lying levels of Sc? are measured by time-resolved laser-induced fluorescence(TR-LIF) technique and the quantum beat method in laser-ablation plasma. In the experiment, free atoms were obtained by laser-ablation plasma technique. A nanosecond laser was used to pump the dye laser, and to produceIV continuously tunable wavelength pulses. In order to expand excitation wavelength range, the second and third harmonics of the dye laser as well as their Stokes or anti-Stokes components were also used. Using TR-LIF technique free atoms populated in lower energy levels can be selectively excited to the aim energy levels and the fluorescence decay signal emitted from the excited states were recorded for time estimation by fast time detection technology. The lifetimes were determined by fitting the fluorescence decay curves with a computer. In the interaction region of laser and ablation plasma the Earth's magnetic field was compensated to within ±0.01 G through three pairs of orthogonal Helmholtz coils. Quantum beat method was employed to detect the fluorescence decay curve involving hyperfine quantum beats.The observed hyperfine quantum beat spectra were analyzed and the magnetic-dipole HFS constants A as well as the electric-quadrupole HFS constants B of these levels were obtained by Fourier transform and a program for multiple regression analysis.This paper mainly concludes three contents as follows:1. The HFS constants of the 4s2 nd 2D3/2(n = 6–18) Rydberg sequence and 4s26p2P3/2 level for two isotopes of 71 Ga and 69 Ga atoms were measured by means of quantum beat method. An apodization procedure was used in the analysis of the quantum beat curve, and the apodized curve was transformed into the frequency domain using Fourier transform. After the filtering processes performed once or twice,all the HFS beat frequencies involved in fluorescence curve could be eventually determined. From these frequency data, the A and B constants for the levels of Ga? were calculated by multiple regression analysis. The HFS constants values obtained are in the range from 0.44 to 34.41 MHz, the uncertainties of our A constants are within 10%. To our best knowledge, the HFS constants of the 4s2 nd 2D3/2(n = 6–18)Rydberg sequence were reported for the first time. The differences between our and previous results of the 4s26 p 2P3/2 level are less than 3%. The nuclear moment ratios between 71 Ga and 69 Ga were obtained, an agreement within errors is achieved by comparison with previous measurements.2. The room-temperature lifetimes of the 4s2ns(n = 11–17) and 4s2nd(n = 6–18)Rydberg sequence and 4s26 p 2P3/2 level for Ga? were measured by means of TR-LIFtechnique. To our knowledge, lifetimes of 15 levels are reported for the first time. The lifetimes lie between 69.5 to 2279 ns, the uncertainties of our lifetime results are less than 10%. We gave the qualitative analysis about blackbody radiation and configuration interaction which can affect measurements of lifetimes of Rydberg levels. We determined blackbody radiation depopulation rates for Ga? levels by using Rb data and obtained Ga lifetimes at 0 K.3. Radiative lifetimes of 38 levels of Sc? were measured by means of TR-LIF technique. The energy regions are from 16021.82 to 48582.13 cm-1. The measured lifetime values range from 9.6 to 1034 ns, to our knowledge, 31 lifetimes results of high-lying levels of Sc? are reported for the first time. According to the electric dipole transition selection rule, the possible angular momentum J values were determined for6 high-lying levels of Sc?.In summary, 13 HFS constants of and 15 lifetimes of Rydberg levels of Ga? and31 lifetimes results of high-lying levels of Sc? were determined by means of quantum beat method and TR-LIF technique. These innovative atomic data have irreplaceable important scientific and application value in the area of atomic structure theory development, hyperfine astronomical spectral analysis, element abundance determination etc.