Inverse hook method for measuring oscillator strengths for transitions between excited atomic states [1]

We describe an effective new method to measure the oscillator strengths for transitions between the excited states of atoms. The oscillator strength is determined, by measuring changes in the angular distribution or polarization of fluorescence light emitted by atoms in the initial or final state of the transition of interest, after these atoms have been subject to the a.c. Stark shift of an off-resonant laser pulse. The physics of the situation is very similar to that of the conventional hook method with this difference: the roles of the atoms and the photons have been interchanged. We therefore call this new methodthe inverse hook method. The inverse hook method is relatively insensitive to the details of the atomic absorption lineshape and also to the temporal and spectral profile of the laser pulse. It yields absolute oscillator strengths and it is especially suitable for measurements of transitions between excited atomic states, including autoionizing states.     

Quantum defect method applied to oscillator strengths

We use ideas from quantum defect theory to obtain approximate energy levels and oscillator strengths. The results are easily obtained, require little computer capability, and typically agree with detailed calculations to better than 5%. The method can be applied to cases where hydrogenic and scaling techniques are inappropriate.     

Ni I oscillator strengths

Oscillator strengths of 150 Ni I lines in the spectral range 2800–6200 Å have been obtained by emission and from hook measurements. Relative sets of ?-values were determined by combining emission measurements on a hollow cathode with hook measurements in a high-temperature furnace. No assumption concerning the plasma state is used, and no temperature determination is required. The relative measurements have been placed on an absolute scale by using lifetime data. The uncertainty of the ?-values is 13% on average. Comparisons are made with the results of other authors.     

类Na离子振子强度的相对论效应

 采用相对论和非相对论原子自洽场方法,计算了类Na离子（原子序数为11~92）的3s-np,3p-ns和3p-nd跃迁过程的激发能和光学振子强度;通过比较相对论与非相对论的结果,研究了M壳层电子的相对论效应随原子序数的变化规律。结果表明：对n=3的跃迁过程,相对论效应主要是影响激发能,对线强度(或跃迁矩阵元)的影响不重要;对于n>3的跃迁过程,相对论效应同时影响线强度和激发能,通常对线强度的影响更大。这些结果对惯性约束聚变和X射线激光研究中需要的不透明度参数计算有重要的参考意义。     

Theoretical term energies and oscillator strengths for carbon

Thomas-Fermi-Hartree-Fock wave functions have been calculated for nl-terms of carbon C(I) (n≤10 and l≤3) and employed to calculate electric dipole oscillator strengths for all allowed transitions between these terms. The dipole length and velocity form of the calculated f-values agree well with the available measurements.     

Improved phase method for determination of relative oscillator strengths: application to Cr II

Among spectro-interferometric methods the hook method has been widely used because of the simple data reduction procedure employed. This paper demonstrates how the spectro-interferograms can be analyzed to obtain f-values of significantly higher accuracy by using Fourier analysis rather than applying the classical hook method or phase methods based only on fringe peak detection techniques.     

Theoretical ionization energies and oscillator strengths for carbon

Frozen core Hartree-Fock wave functions have been calculated for 98 excited s-, p- and d-levels of C(I), and employed to calculate electric dipole oscillator strengths for all allowed transitions between these levels. The energy levels generally agree with observations to within 1.3% and the length and velocity forms of the calculated л-values agree well except for very weak transitions.     

Optical oscillator strengths for the sulphur isoelectric sequence

An analytic atomic independent-particle-model potential, adjusted to experimental energy levels, is used to calculate optical oscillator strengths for S, Cl⁺¹, Ar⁺², K⁺³, Ca⁺⁴ and Sc⁺⁵.     

类Na离子振子强度的相对论效应

采用相对论和非相对论原子自洽场方法,计算了类Na离子（原子序数为11~92）的3s-np,3p-ns和3p-nd跃迁过程的激发能和光学振子强度;通过比较相对论与非相对论的结果,研究了M壳层电子的相对论效应随原子序数的变化规律。结果表明：对n=3的跃迁过程,相对论效应主要是影响激发能,对线强度(或跃迁矩阵元)的影响不重要;对于n>3的跃迁过程,相对论效应同时影响线强度和激发能,通常对线强度的影响更大。这些结果对惯性约束聚变和X射线激光研究中需要的不透明度参数计算有重要的参考意义。     

Determination of oscillator strengths for UI and UII lines

The emission spectrum of a uranium plasma obtained in a hollow cathode was studied to determine plasma characteristics of uranium atoms such as temperature plasma-excitation, temperatures of neutral species, and oscillator strengths (gf values) of more than 370 lines of the U_I and U_II spectra.     

Optical oscillator strengths for Be II and B III

A simple two-parameter analytic potential adjusted so as to produce the experimental energy levels is used to generate wave functions for the ground and excited states of the ions Be II and B III. Using these wave functions we calculate optical oscillator strengths for various excitations from the 1s ²2s(² S) ground state. The results are compared to experiment and other calculations.     

Theoretical determination of oscillator strengths for the principal series of rubidium-like ions by the Dirac-Fock method

A simple formula that allows the determination of the oscillator strengths for all transitions of principal series of the Rb-like ions is obtained from the relationship between the oscillator strengths and the corresponding photoionization cross sections. The photoionization cross sections are calculated by the Dirac-Fock method with allowance for the retardation and approximated by an analytic formula. The data for ten ions of the rubidium isoelectronic sequence (from Sr⁺ to Ag¹⁰⁺) are presented. Two types of gauges corresponding to the transition operators in length and velocity forms are considered.     

Lifetimes and oscillator strengths of neutral vanadium

Oscillator strengths of 105 V(I) lines in the spectral range 2800–6000 Å were obtained by lifetime, emission, and hook measurements. Relative sets of ?-values were determined by combining emission measurements on a hollow cathode with hook measurements in a high temperature furnace, whereby no assumption concerning the plasma state is used and no temperature determination is required. The determination of the radiative lifetimes was performed by selective laser excitation of an atomic beam of vanadium and time-resolved observation of the reemitted fluorescence after the pulse. The absolute ?-values have an uncertainty of 12% on average. Both for the lifetimes and the ?-values a comparison with literature data is performed.     

Ultraviolet oscillator strengths for carbon,nitrogen and oxygen ions

Oscillator strengths were calculated for u.v. transitions in carbon, nitrogen and oxygen ions. Single and multiconfiguration numerical Hartree-Fock wavefunctions were used to represent initial and final states of the various transitions, and both dipole length and dipole velocity transition matrix elements were calculated. A careful choice of a few important configurations leads in most cases to multiconfiguration results which are in good agreement with experiment, and with other theoretical calculations.     

Experimental investigations of oscillator strengths for ultraviolet transitions in LaII

f-values for ultraviolet transitions from nine excited levels in LaII have been deduced by a combination of lifetime and branching ratio measurements using time-resolved laser spectroscopy and the emission spectrum from a hollow cathode lamp. Part of the present results is compared with previous results. Received 10 February 1999 and Received in final form 22 April 1999     

Weighted oscillator strengths and lifetimes for the S XIV spectrum

The weighted oscillator strengths gf and the lifetimes for S XIV presented in this work have been calculated in a multiconfigurational Hartree–Fock relativistic approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure in order to improve the adjustment to experimental energy levels. This method produces gf values that are in better agreement with observed line intensities and lifetime values closer to the experimentally determined ones. In this work we presented all the experimentally known electric dipole S XIV spectral lines. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 473–476, 2009.     

Theoretical oscillator strengths for the NI and OI resonance transitions

We report results from the first many-body calculations of the important oscillator strengths of the resonance lines NI $\text{1s}{}^2\text{2s}{}^2\text{2p}{}^3{}^4\text{S°?is}{}^2\text{2s}{}^2\text{2p}{}^2\text{3s}{}^4\text{P(λ=1200}\text{A}\text{?}\text{), 1s}{}^2\text{p}{}^2\text{3d}{}^4\text{P(λ=953}\text{A}\text{?}\text{)}$ and OI $\text{1s}{}^2\text{2s}{}^2\text{2s}{}^2\text{2p}{}^4{}^3\text{P ?1s}{}^2\text{2s}{}^2\text{2p}{}^3\text{3s}{}^3\text{S°(λ = 1304}\text{A}\text{?}\text{)}$. Our values are: $\text{?(1200)=0·271; ?(1304)=0·047; ?(953)= ·082}$. The first two are in excellent agreement with recent lifetime and absorption measurements and thus the existing discrepancy between theory and experiment is resolved. The third number constitutes the only available result for this transition.     

Weighted oscillator strengths and lifetimes for the Si II spectrum

The weighted oscillator strengths (gf) and the lifetimes for Si II presented in this work were carried out in a multiconfiguration Hartree–Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we presented all the experimentally known electric dipole Si II spectral lines.     

On peculiarities of generalized oscillator strengths for ionization from p-states

Exact expressions are given in the Born approximation for the density of the generalized oscillator strenghts of hydrogen-like particles for electron transitions from the states 3p₀ and 3p_±1 into the continuum with zero energy. The peculiarities of the generalized oscillator strengths are considered.     

An accuracy check for relative oscillator strengths using an intensity/linewidth method applied to precise data

A new intensity/linewidth method of opacity measurement is applied to a published set of precise Fourier transform spectrometer measurements for the purpose of establishing the accuracy of literature values of relative Fe II oscillator strengths. Eight sets of oscillator strength values are compared, including recent experimental values of Bergeson et al. (1996) and new theoretical values of Raassen and Uylings (1998). Remarkably good agreement between linewidth-predicted and intensity-derived intensity reduction factors is found using the recent values, in the process verifying the method itself.