Investigations On Radiative Parameters And Landé Factor Of Cr Ⅰ, Tm Ⅰ, Tm ⅡAnd Eu Ⅲ Levels

Structural parameters and radiative parameters of atoms are extremely important basic data for the investigation of the atomic physics, the analytical chemistry, the plasma physics, the astrophysics, and so on. The data of radiative lifetimes and Landé factors will be helpful to understanding angular momentum coupling schemes, the dynamic behavior of electrons, the atomic structure and radiative properties of highly excited states in atomic physics. In astrophysics, the radiative parameters such as reliable oscillator strengths are important atomic radiative parameters since they are used to derive the age of the celestial bodies, the element chemical compositions, and physical nucleosynthesis processes in stars. Some rich stellar spectra of iron-peak and rare-earth elements are detected in some chemically peculiar star and the hot star cluster, by analyzing of these spectra can determined the elements high cosmic abundance, and it is necessary of studying the structural parameters and radiative parameters of iron-peak and rare-earth elements.Radiative lifetimes of Cr I, Tm I, Tm II and Eu III and Landé factor of Cr I are measured by time-resolved laser-induced fluorescence and Zeeman quantum beat methods in laser-ablation plasma. In the lifetime measurements, 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. The excitation pulse populated the low-lying metastable levels as well as the ground states to the aim excited levels. The fluorescence light emitting from excited level was collected with a lens onto the entrance slit of a monochromator and detected by a photomultiplier tube(PMT). Then, the time-resolved fluorescence signals from the PMT were recorded and averaged by a digital oscilloscope and stored in the computer for evaluating the lifetimes by fitting the fluorescence decay curve to a convolution of the detected laser pulse and a pure exponential function for the levels of shorter lifetimes or by a least-squares exponential fitting to the decay part of fluorescence curve for the long-lived excited levels. In the Landé factor experiment, the excitation laser was polarized perpendicularly to the external magnetic field to induce σ transitions and the fluorescence was detected along the field and a linear polarizer in front of the monochromator slit controlled its polarization. The beat frequency can be more precisely evaluated from the quantum beat curve by Fourier analysis. Then, Landé gJ factors can be deduced by the equation. In the measurements, some systematic effects on lifetime value such as the flight-out-of-view effect, radiation trapping, and saturation and collision effects were eliminated by changing the experimental conditions such as pulse energies of the ablation and the exciting light, the ablation-excitation delay time of the two lasers, the size of the focus, the monochromator position and the slit width, and so on. We also must be careful of the co-excitation to make sure that only a studied level was excited correctly at a time.Transition probabilities and oscillator strengths were determined by combining the lifetimes with the branching fractions. In the branching fraction measurements, a hollow-cathode lamp was used to produce emitting spectra for atom and ion, and a high resolution grating spectrometer was used to obtain the element emitting spectra. By analyzing the intensites of the spectra, the branching fractions for the atomic transitons were determined.In this paper, Landé gJ factors of 35 levels and radiative lifetimes of 43 levels in the 3d54p、3d44s4p、3d55p and 3d44s5 p configurations of Cr I in the energy from 23305.0026 to 53782.78 cm-1 were measured by time-resolved laser-induced fluorescence(TR-LIF) and Zeeman quantum beat methods in laser-ablation plasma. Good agreements between the present results and the previous experimental values were achieved for both gJ factors and lifetimes. The measured gJ values are quite close to those calculated under pure LS-coupling scheme. The lifetime values obtained are in the range from 11.4 to 193 ns. To our knowledge, the results of 15 Landé factors and 17 lifetimes are reported for the first time. Based on the emission spectrum of a hollow cathode lamp, branching fraction measurements of 8 levels for Cr I were performed. Combined the measured lifetimes with the branching fractions, absolute transition probabilities and oscillator strengths for 31 transitions were derived. Radiative lifetimes of 88 levels belonging to the 4f125d6s6p、4f126s26p、4f136s8s、4f125d6s2、4f136s6p、4f136s7p、4f135d6p and 4f136s8 p configurations of Tm I in the energy range 22791.176 to 48547.98 cm-1 and 29 levels belonging to the 4f126s6p、4f125d6p、4f125d6s、4f125d2 and 4f126s2 configurations of Tm II in the range 27294.79 to 65612.85 cm-1 were measured by TR-LIF method in laser-ablation plasma. The lifetime values obtained are in the range of 15.4-7900 ns for Tm I and from 36.5-1000 ns for Tm II. To the best of our knowledge, 77 lifetimes of Tm I and 22 lifetimes of Tm II are reported for the first time. Good agreements between the present results and the previous experimental values were achieved for both Tm I and Tm II. Radiative lifetimes of 6 levels belonging to the 4f6(7F)5d configurations of Eu III in the energy range 39636.83 to 42530.91 cm-1 are measured using the TR-LIF method. The lifetime range from 33 to 130 ns and the uncertainties of these measurements are within ±10%. Among the results, three levels are first measured.In summary, some new structural parameters and radiative parameters of atoms are acquired by measuring the value of the radiative lifetimes, Landé factors and branching fractions of Cr I and the radiative lifetimes of Tm I, Tm II, Eu III in this work. These results not only further supply the rich spectral data needed urgently in determination of the solar chemical composition, but also are of great value for the investigations in many field such as nuclear fusion physics, atomic physics, and plasma physics.