Oscillator strengths and transition probabilities of the Be(I) isoelectronic sequence for 2p2-2s2p and 2s2p-2s2 transitions

Oscillator strengths and transition probabilities are obtained from an intermediate coupling scheme. The initial basis of the eigenstates is formed inLS-coupling. To obtain the resulting energy matrix,Z^-1 perturbation theory is applied. The values of oscillator strengths and transition probabilities for 1s²2p²?1s²2s2p and 1s²2s2p?1s²2s² transitions are calculated and the comparison is made with some recent results. The nuclear charges (Z) involved varied fromZ=4(Be(I)) toZ=35(Br(XXXII)).     

Model-potential oscillator strengths for 4fn6s2–4fn6s6p transitions in Sm(I), Eu(I), Dy(I), Er(I) and Yb(I)

The 4fⁿ6s²?4fⁿ6s6p transitions are studied for neutral samarium, europium, dysprosium, erbium, and ytterbium. Four different couplings between the valence electrons and the 4fⁿ shell are considered, three are based on the LS and one on the J_IJ_II scheme. The radial integrals are computed with the model-potential method, which includes both exchange and core polarization. The results are compared with those obtained by employing the Coulomb approximation and the ab initio Hartree + Exchange (HX) approach, as well as with available experimental data. The core-polarization influence on oscillator strengths for these transitions is also investigated.     

Z-dependences of atomic characteristics of ions in Be- and O-isoelectronic sequences (2s−2p transition)

Transition energies and probabilities are presented for ions of the Be(Z = 4?100) and O(Z = 8?100) isoelectronic sequences. Dipole transitions are considered between all low-lying states constructed from 2s², 2s2p, and 2p² configuration in the case of Be-like ions, and between all low lying states from 2s²2p⁴, 2s2p⁵, and 2p⁶ configurations in the case of O-like ions. The calculations are based on the $\text{1}\text{Z}$ expansion technique and are carried out in the intermediate coupling scheme. Relativistic effects are incorporated using the Breit operator. For Z > 40, it is shown that jj-coupling is applicable. Results of the present calculations are compared with those of other authors over a broad range of nuclear charges.     

Relativistic calculations of 3s2 1S0-3s3p 1P1 and 3s2 1S0-3s3p 3P1,2 transition probabilities in the Mg isoelectronic sequence

Using the multi-configuration Dirac-Fock self-consistent field method and the relativistic configuration-interaction method,calculations of transition energies,oscillator strengths and rates are performed for the 3s 2 1 S 0-3s3p 1 P 1 spinallowed transition,3s 2 1 S 0-3s3p 3 P 1,2 intercombination and magnetic quadrupole transition in the Mg isoelectronic sequence(Mg I,Al II,Si III,P IV and S V).Electron correlations are treated adequately,including intravalence electron correlations.The influence of the Breit interaction on oscillator strengths and transition energies are investigated.Quantum electrodynamics corrections are added as corrections.The calculation results are found to be in good agreement with the experimental data and other theoretical calculations.     

Oscillator strengths for 3dn4s → 3dn4p transitions in the iron series

The observed oscillator strengths for the 3dⁿ4s → 3dⁿ4p transitions in the iron series show anomalous behaviour for Cr and Mn : the former is exceedingly small whereas the latter is unusually large.Theoretical Hartree-Fock gf-values are reported and a considerable discrepancy with experimental values is noted for Cr. The effect of the interaction of 3dⁿ4p with 3d^n?14s4p is studied using a fixed core, multi-configuration Hartree-Fock approximation. This interaction does not improve significantly the agreement with observed values.     

Relaxation of the Ne(2p1) level and populations of Ne(1s2) and Ne(1s4) in an afterglow

Radiation trapping of the transition 2p₁-1s₂ of neon has been demonstrated during laser-induced fluorescence in a pulsed microwave discharge through neon. The population of Ne(1s₂) atoms is deduced. Selective excitation is useful for the determination of lifetimes and cross sections of collisions with neutral atoms. The results may be utilized in processes for the creation of metastable atoms.     

Theoretical study of the AlO blue-green (B2∑+−X2∑+ band system

Two independent, extensive theoretical calculations are reported for the relative band strengths of the AlO (B²∑⁺?X²∑⁺) blue-green system and for the radiative lifetimes of the lowest few vibrational levels of the B²∑⁺ state. The theoretical lifetimes, which include a small (<0.5%) contribution from bound-bound transitions into the A²Π state, are in excellent agreement with laser fluorescence studies. The theoretical lifetimes increase monotonically and very slowly with increasing vibrational quantum number. The relative band strengths for the blue-green system derived from the two theoretical calculations are in excellent agreement, but differ systematically from the relative band strengths of Linton and Nicholls. Our results suggest that their self-absorption corrections are not large enough, resulting in relative intensities that are too large, especially for the weak bands with r centroids less than 1.5Å.     

Observation of the radiative 2s02p6−2s12p5 transition in NeIII

Ion impact excited spectra of Ne contain a line at 52.82 nm which has been identified as resulting from the decay of double 2s vacancies in NeIII via the transition 2s⁰2p⁶(¹S₀)?2s¹2p⁵(¹P₁).     

Theoretical study on behaviors of 1s22s-1s2np transition for Co24+ ion in the whole energy region

Non-relativistic energies of 1s²2s and 1s² np (n⩽9) states for Co²⁴⁺ ion are calculated by using the full-core plus correlation method. Our results of 1s²2s and 1s²2p states agree well with the high-precision results of Yan et al. Based on calculating the first-order corrections to the energy from relativistic and mass-polarization effects, we estimate the higher-order relativistic contribution and QED correction to the energy under a hydrogenic approximation. The transition energies, wavelengths and oscillator strengths for the 1s²2s−1s² np (n⩽9) transitions of this ion are calculated. The results agree with the experimental data available in literature satisfactorily. By combining with quantum defect theory, our theoretical predictions on the energy and oscillator strength of this ion are extrapolated to the whole energy region including continuous states.     

The shape of the 11S0 − 21P1 Fano resonance in the H- photo-ionization continuum

The interaction between the discrete autoionized state 1s2p of negative hydrogen and the overlapping split-configuration continuum is described in terms of stationary perturbations of nonorthogonal states that are eigenstates of two different first-order approximations to the Hamilton operator for the system.The eigenfunctions for the split-configuration states are taken to be those of a free p electron outside a neutral hydrogen atom in the ground state. The eigenfunction adopted for the short-lived, closed 1s2p configuration is the product of two functions that belong to symmetric Hartree-Fock eigenfunctions for the 1s²¹S and 2p²¹D states, respectively. This eigenfunction defines that Hamilton-operator approximation, of which the 1s2p state is an eigenstate.An improved Hamilton operator defines two different, but not independent, perturbation functions, one of which is a measure of the instability of the 1s2p configuration. The width of the resonance is found, correspondingly, to be determined by the product of two different perturbation terms. They are calculated in a Hartree-type approximation and found to be small, in part due to an effect of the nonorthogonality of the unperturbed states.The mean position of the singlet and triplet P Fano resonances in the ground state absorption continuum of H^- is found to be close to that of the diffuse interstellar bands at λ4430 and λ4760, but the calculated distance is about four times that of the bands. With exchange neglected and the position of maximum absorption fixed at λ4430 the singlet P resonance is found to have a width of 43 Å at half maximum, a minimum on the short-wave-length side, and a top absorption coefficient of 7 × 10^-16 cm²/ion, corresponding to an f value equal to 0.27.Tables of Hartree-Fock functions for the 2s²¹S, and the 2p²¹S, ¹D and ³P states of H^-, calculated by Claus Ingemann-Hilberg, are given in an appendix.     

Electronic transition-moment variation in the A1π-X1Σ system of the GeO molecule

The spectrum of GeO was excited in a carbon arc and the relative band intensities were measured by using photographic photometry and were then interpreted in terms of Franck-Condon factors. It was found that the electronic transition moment varies as Re(r)=constant×(1-0.476r-0.061r²), where 1.62?r, Λ?1.82. Using this relation, smoothed band strengths, band-oscillator strengths and Einstein coefficients of the bands were calculated using expressions given by Penner. The effective vibrational temperature is estimated to be 1090 K. The average life times of the v′=0 and 1 vibrational levels have also been estimated.     

Transition energies, wavelengths, oscillator strengths and transition probabilities between 1s, 1sns and 1snp (2?n?9) states for He-like Silicon

Multiconfiguration Hartree-Fock calculations with Breit-Pauli relativistic corrections are reported for electric dipole transition (E1) energies, wavelengths, weighted oscillator strengths and transition probabilities between all of the 1s², 1sns and 1snp (2?n?9) states for He-like silicon. The results are found to compare very well with available other results except Δn=0 due to differences in the calculated excitation energies.     

Franck-Condon factors and R-centroids for the A1∑+-X1∑+ and B3Π(0+)−X1∑+ band system of 63Cu1H and 63Cu2H

The recently reported new RKR potential energy curves for the X¹∑⁺, A¹∑⁺, and B³Π(0⁺) electronic states of ⁶³Cu¹H and ⁶³Cu²H are used to calculate Franck-Condon factors and r-centroids for the A?X and B?X band systems for 0≤v″≤20, 0≤v′≤10 and J = 0, 30, 40. The r-centroid approximation is verified and a physical interpretation of the r-centroid is discussed.     

Determination of the B1Π-X1Σ and C1Σ-X1Σ electronic transitions strengths of CaO

The strengths S_e of the B¹Π-X¹∑ and C¹∑-X¹∑ electronic transitions of the CaO molecule have been determined by absorption measurements in a shock tube. Powdered calcium oxide and a gaseous mixture of oxygen and argon in the ratio of 1:5 or 1:9 were introduced into the shock channel. The CaO gas-phase concentration was determined by using the equilibrium constant for CaO?Ca+O; atomic oxygen concentration was calculated and that of calcium was measured spectroscopically. The values of S_e (in atomic units) are for B¹Π-X¹∑, 2.32±0.49; for C¹∑-X¹∑, 2.88±0.67.     

Screening constant by unit nuclear charge calculations for (n s2)1Se, (np2)1De and (N s n p)1P○ excited states of He-like systems

Screening Constant by Unit Nuclear Charge (SCUNC) is a new analytical method suitable for the treatment of the properties of He-like systems. In this paper, the possibilities of the method are demonstrated for calculating in the framework of semi-empirical procedure, total energies, total electron-electron interaction energies and excitation energies for (ns²)¹S^e, (np²)¹D^e and (Nsnp)¹P° doubly excited states of He-like ions. The proposed semi-empirical scheme, leads to accurate results in good agreement as well as with available other theoretical results than experimental data.     

Absolute band strengths for the AlO blue-green (B2σ−X2σ) band system

The relative intensity measurements of Linton and Nicholls¹ on the AlO blue-green system have been placed on an absolute scale using the radiative lifetimes of Johnson et al.² and Dagdigian et al.³ for levels of the B²Σ state of AlO. Absolute values of Einstein A coefficients, band strenghts and band oscillator strengths are presented for 75 bands of the system.     

Determination of the B1II-X1Σ and C1Σ-X1Σ electronic transitions strengths of CaO

The strengths S_e of the B¹II-X¹Σ electronic transitions of the CaO molecule have been determined by absorption measurements in a shock tube. Powdered calcium oxide and a gaseous mixture of oxygen and argon in the ratio of 1:5 or 1:9 were introduced into the shock channel. The CaO gas-phase concentration was determined by using the equilibrium constant for CaO?Ca + O; atomic oxygen concentration was calculated and that of calcium was measured spectroscopically. The values of S_e (in atomic units) are for B¹II-X¹Σ, 1.7 ± 0.5; for C¹Σ-X¹Σ, 2.1 ± 0.6.     

Direct extraction of the isovector deformation parameter β(1)2 from the (p,n) reaction of 56Fe

The reaction ⁵⁶Fe(p, n)⁵⁶Co leading to the analog of the ground state and the first excited 2⁺ state of ⁵⁶Fe has been studied at E_p=20, 28, 32 and35MeV. The direct process dominates at higher energies, thus the direct extraction of the isovector deformation parameter β⁽¹⁾₂ is feasible. It is found that β⁽¹⁾₂ is about three times larger than β⁽⁰⁾₂, the isoscalar deformation parameter.     

Optical absorption spectra of s2 impurity ions in aqueous halide ion glasses

The optical absorption bands of aqueous 0·05 M Sn²⁺ in 7 M LiI at 77°K appear at 361, 352, 325, 310, 300, 292 and 262 nm. They are considered to be the A₁, A₂, B, C₁, C₂, C₃ and D′ bands since the positions and relative intensities lie within the range of those bands for Sn²⁺-doped alkali iodide crystals. Upon warming the glass there is an uncorrelated increase in the B band and a decrease in the A₁ band. In 3·6, 4·1, 4·6 and 5·1 M CaCl₂ glasses with 5×10^?3 M Sn²⁺ the A₁ and A₂ bands show uncorrelated increases with increasing concentration of Cl^?. Comparable observations are reported for Pb²⁺-doped glasses of lithium halides and CaI₂. In general the spectra of the Sn²⁺- and Pb²⁺-doped glasses correlate well with those of the corresponding crystal systems. The effect of temperature and halide-ion concentration are attributed to shifts in chemical equilibria among the well-known halo complexes, MX_n^2?n MX_n?1^1?n+X^?, each having a characteristic, absorption and emission. Absorptions may be attributed to M²⁺(³P₁ ← ¹S₀) and M²⁺(¹P₁ ← ¹S₀) in the complex, shifted by partially covalent bonding of n halide ions.     

Investigation of π−(π+)+4He→π+(π−) + 4n (4p) reactions

The $\text{π}{}^{\mathrm{?}}\text{(π}{}^{\mathrm{+}}\text{) +}{}^4\text{He→π}{}^{\mathrm{+}}\text{(π}{}^{\mathrm{?}}\text{) + 4n (4p)}$ reactions are investigated in the framework of the four-body hyperspherical basis method. It is shown that the effect of the final state interaction between four nucleons is very significant and these nucleons are mainly in the state with total orbital momentum L=0.