Investigations On Radiative Parameters Of Ⅵ, EuⅡ, GdⅠ And ⅡLevels

Radiative parameters of atoms and ions such as natural radiative lifetimes,transition probabilities, and oscillator strengths, etc. are essential for the investigationof the plasma physics, the atomic physics, the astrophysics, and so on. It was foundthat the iron elements and the rare-earth elements have relatively high abundance inmany stars such as solar and some CP stars. The analyses for the astronomical spectraof these elements are helpful for understanding the nucleosynthesis in stars,determining the ages of the celestial bodies and the element chemical abundance, andso on. So the measurements and investigations for the radiative parameters are ofgreat significance. However, the available data are not complete, and some of themhave serious deviations. Consequently, the radiative lifetimes for some levels in V I,Eu II, Gd I and II were measured in this paper, and furthermore the relative transitionprobabilities and oscillator strengths were determined by combining the lifetimes withthe branching fractions.The time-resolved laser-induced fluorescence (TR-LIF) technique was used toobtain radiative lifetimes in this paper. During the lifetime measurements, a laser wasused to produce free atoms and ions. Another laser was used to pump the dye laser,and to produce continuously harmonious wavelength pulses. The ultraviolet (UV)excitation pulses were obtained by the BBO crystals and stimulated Raman scattering(SRS) device. The free atoms or ions in the vacuum chamber were excited selectivelyby the excitation pulses. The emitted fluorescence from the aimed level was detectedand recorded by a monochromator, a photomultiplier (PMT), and an oscilloscope. Thelifetimes were determined at last by fitting the fluorescence decay curves with acomputer.The measured lifetimes can be used to deduce transition probabilities and oscillator strengths by combing with the branching fractions. During the branchingfraction measurements, a hollow-cathode lamp was used to produce emitting spectrafor atom and ion, and a high resolution grating spectrometer was used to obtain theelement emitting spectra. The branching fractions for the atomic transitions weredetermined by analyzing the intensities of the spectra.In this paper, radiative lifetimes of54levels belonging to the3d34s4p,3d44p,3d34s5p,3d45p and3d34s4d configurations of V I with energy from26604.807to46862.786cm1have been measured using time-resolved laser-induced fluorescence(TR-LIF) spectroscopy in laser-produced plasma. The lifetime values reported in thispaper are in the range of3.3494ns, and the uncertainties of these measurements arewithin±10%. A good agreement was obtained with previous data. The Hartree-Fockwith relativistic corrections method (HFR) which we have included core-polarization(CPOL) effects was used to calculate the lifetimes, the branching fractions and thetransition probabilities in V I by cooperating with Professor Quinet’s team at MonsUniversity in Belgium. Radiative lifetimes for30even-parity levels in the4f65d6s,4f65d2and4f8configurations with the energy range between34923.43and57388.87cm–1of Eu II were measured by TR-LIF method. Branching fraction measurements of7levels for Eu II were performed based on the emission spectrum of a hollow cathodelamp. By combining the measured lifetimes and the branching fractions, absolutetransition probabilities and oscillator strengths for18transitions were derived.Radiative lifetimes of27levels in Gd I and27levels in Gd II have been measuredusing TR-LIF method. The measured lifetime values range from4.0to90ns with anuncertainty of5%or less. Branching fractions of13levels in Gd I and12levels in GdII were experimentally determined based on the emission spectrum of a hollowcathode lamp. In addition, transition probabilities and oscillator strengths for66linesof Gd I and74lines of Gd II were derived from a combination of the radiativelifetimes reported in the earlier literatures and the branching fractions obtained in thepresent paper. The measured lifetimes, transition probabilities, and the oscillatorstrengths are all in good agreements with the previous ones.IV In summary, the radiative parameters for V I, Eu II, Gd I and II were measuredand calculated systematically in this paper. These results are complementary forspectrum data which are used in the atomic physics theory and astrophysical spectrumanalysis. Furthermore, these data can also be applied in the fields such as laser physics,plasma diagnosis, and nuclear fusion.