The large effects of electron correlation on the multiplet generalized oscillator strengths of non-closed shell systems: Be 1s22s21S → 1s22s2p 1P0 and B 1s22s22p 2p0 → 1s22s2p22D

Correlation effects are shown to change generalized oscillator strengths and inelastic form factors by large factors as large as 10, from the Hartree-Fock values. The effects are fully included in the charge wavefunctions of the non-closed shell many-electron theory by Sinano?lu. We calculate the charge wavefunctions and obtain from the generalized oscillator strength F_0η(q) versus ln q² and the integrated cross section σ_0η(E) versus lnE₁ for BeI 2s²¹S → 2s2p ¹P⁰ and BI 2s²2p ²P⁰ → 2s2p²²D cases, exemplifying the method.     

1s22p3 and 1s22s23l, l = s,p,d, excited states of boron isoelectronic series from explicitly correlated wave functions

For some members of the boron isoelectronic series and starting from explicitly correlated wave functions, six low-lying excited states have been studied. Three of them arise from the 1s(2)2p(3) configuration, and the other three from the 1s(2)2s(2)3l, l = s,p,d, configurations. This work follows a previous one on both the 1s(2)2s(2)2p-(2)P ground state and the four excited states coming from the 1s(2)2s2p(2) configuration. Energies, one- and two-body densities in position space and some other two-body properties in position and momentum spaces have been obtained. A systematic analysis of the energetic ordering of the states as a function of the total orbital angular momentum and spin is performed in terms of the electron-nucleus and electron-electron potential energies and the role of the angular correlation is discussed. All calculations have been carried out by using the Monte Carlo algorithm.     

Lifetimes of the 4s4p 3 P 1 and 4s3d 1 D 2 states of Ca I

The lifetimes of the 4s4p ³ P ₁ and 4s3d ¹ D ₂ metastable states of Ca have been studied using the time-of-flight technique. Two kinds of observations were performed. First, the exponential decay of the fluorescence, using a (continuous) dc discharge for excitation and then the velocity distribution of the radiating atoms, using a pulsed discharge, were measured. From the combined results of these measurements the lifetimes were derived. The lifetimes of the 4s4p ³ P ₁ and 4s3d ¹ D ₂ states of Ca are determined to be 0.57±0.03 ms and 1.5±0.4 ms, respectively.     

Electron-impact excitation of the transition 1s 22s 22p 5(2 P 3 2/0 −2 P 1 2/0 ) of Mg IV

Effective collision strengths for electron-impact excitation of the ground state fine structure transition² P ₃ ^2/0 ?² P ₁ ^2/0 have been calculated by using theR-matrix method. Twelve lowest target states, represented by configuration interaction wavefunctions are included in the scattering calculations.M1 andE2 transition probabilities are also calculated by employing the Breit-Pauli Hamiltonian.     

Solution of the complex eigenvalue Schrödinger equation for the rydberg series of inner hole excited autoionizing states. The Be 1s 2s 2 n p (n=2–5)3 P 0 and1 P 0 series

In the state-specific theory of autoionizing states, the square-integrable wavefunction of complex coordinates corresponding to the complex eigenvalue is separated into terms contributing to the stability of the state and terms contributing to its decay. The choice and optimization of the function spaces describing these terms are different. In this work, taking the inner hole excited Be 1s 2s ² n p Rydberg series as an example, we compute the asymptotic correlation and the concomittant energy shifts and widths by expanding the open channels in terms ofback-rotated generalized Laguerre polynomials and by diagonalizing a complex Hamiltonian matrix where the coordinates of the operator and of the occupied and virtual orbitals are real. Interchannel coupling is determined by mixing the independently optimized asymptotic pair correlation functions via the diagonalization of the total matrix. We found that, as expected, the Auger widths of both³ P ⁰ and¹ P ⁰ series converge as a function ofn to the value of the previously determined width of the Be⁺ 1s 2s ^{2 2} S state. We also computed the oscillator strengths of the transitions Be 1s ² 2s ^{2 1} S→1s 2s ² n p ¹ P ⁰, which had previously been calculated within the time-dependent Hartree-Fock approximation. Forn>2, the discrepancy is large.     

Accurate variational calculations of the ground 2Po(1s22s22p) and excited 2S(1s22s2p2) and 2Po(1s22s23p) states of singly ionized carbon atom

In this article we report accurate nonrelativistic variational calculations of the ground and two excited states of C(+) ion. We employ extended and well optimized basis sets of all-electron explicitly correlated Gaussians to represent the wave functions of the states. The optimization of the basis functions is performed with a procedure employing the analytic gradient of the energy with respect to the nonlinear parameters of the Gaussians. The calculations explicitly include the effects due to the finite nuclear mass. The calculated transition energies between the three states are compared to the experimentally derived values. Finally, we present expectation values of some small positive and negative powers of the interparticle distances and contact densities.     

Lifetime measurements of the 2p 3d 3 D 1, 2, 3 0 and 2p 3d 1 P 1 0 levels in NII by beam-foil-laser spectroscopy

Accurate lifetimes measured by means of the cascade-free method based on laser excitation of a fast ion beam preexcited in a carbon foil are reported for four 2p 3d levels in NII. The lifetime results are: τ(2p 3d ³ D ₁ ⁰ )=0.209±0.007 ns, τ(2p 3d ³ D ₂ ⁰ )=0.219±0.007 ns, τ(2p 3d ³ D ₃ ⁰ )=0.217±0.005 ns, and τ(2p 3d ¹ P ₁ ⁰ )=0.410±0.017 ns. These results are compared to theoretical and experimental lifetimes reported previously.     

Hyperfine structure constants of the CaII states 4s 2 S 1/2 and 4p 2 P 1/2, 3/2 and the nuclear quadrupole moment of43Ca

The hyperfine structure splittings of the 4s ² S _1/2 → 4p ² P _{1/2, 3/2} transitions in⁴³CaII have been measured by fast ion beam collinear laser spectroscopy. The resonant laser interaction was observed using non-optical detection based on optical ground state depopulation pumping, state selective neutralization and charge state separated particle counting. The extracted magnetic dipole hyperfine structure constants for⁴³CaA(² S _1/2)=?805(2) MHz,A(² P _1/2)=?145.5(1.0) MHz andA(² P _3/2)=?31.9(0.2) MHz are in excellent agreement with relativistic many body perturbation theory predictions available for this alkali-like ion. The combined results are used to evaluate the semi-empirical analysis method. From the electrical quadrupole hyperfine structure constantB(² P _3/2)=?6.7(1.4) MHz and the calculatedB/Q value for this one valence electron configuration, the nuclear quadrupole momentQ(⁴³Ca)=?0.043(9)b is derived. This result supports a previous evaluation based on the hyperfine structure of the two valence electron³ P configurations of CaI.     

Spectroscopy and kinetics of the 1P1 and 3P2 states of Hg 6s6p in xenon

The spectra and kinetics observed following excitation of Hg 6s6p(¹P₁) in xenon show the occurence of complex attachment and relaxation processes. The ¹P₁ attaches to Xe in termolecular collisions to produce HgXe E¹1, which emits a broad band with λ_max ≈ 2150 Å. Addition of krypton to Hg, Xe mixtures enhances the E-state emission by atom exchange with an HgKr^* complex. The E state also undergoes collisional deactivation by Xe, rate coefficient (1.75 ± 0.25) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, to generate ³P₂. However, the predominant route for ³P₂ formation is via collision of ¹P₁ with Xe, rate coefficient ≈ 4 × 10⁻¹² cm³ molecule⁻¹ s⁻¹. With [Xe] at 760 Torr, about 75% of the generated ³P₂ is attached in the form of the HgXe(C ³2) complex; lifetimes up to 600 μs have been observed. Two new emission bands occur when ³P₂ is prepared in xenon. A sharp feature, slightly blue-shifted from the forbidden ³P₂:¹S₀ line, results when ³P₂ and Xe approach on the D ³1 surface. The other band is broad with λ_max ≈ 2520 Å; the carrier is assigned to an HgXe₂(³2_u) complex. Rate coefficients for deactivation of ³P₂ to lower ³P_J states have been measured.     

Stark-mixing effect on the 6p 2 1 S 0−6p 2 3 P 2 transition in Pb I

The intensity of the 531.5 nm electric-field-quench radiation has been measured on a thermal beam of neutral Pb atoms in the metastable 6p ^{2 1} S ₀ state. The measurement yields a Stark-mixing amplitude for transition between the 6p ^{2 1} S ₀ and 6p ^{2 3} P ₂ states. Combining this result with available experimental data sets an upper limit for the 6p 7s ³ P ₁ → 6p ^{2 1} S ₀ transition probability:A _ki <1.79·10³ s ^?1. Calculations for the 6p 7s → 6p ² and 6p 8s → 6p ², as well as transition rates of forbidden lines inside 6p ² configuration of PbI are presented and compared with existing experimental data.     

Effect of the exchange integral K2s2p on the 2p-orbitals of the 1P and 3P states of the beryllium isoelectronic sequence arising from the configuration (1s)2(2s)(2p)

The ¹P and ³P states arising from the configuration (1s)²(2s)(2p) of the Be isoelectronic sequence are investigated. In the single configuration approximation, the energies of the two states are expressed as E⁰ + K_2s2p and E⁰ - K_2s2p, respectively. K_2s2p is the exchange integral between the 2s and 2p electrons and E⁰ is the energy of a model in which K_2s2p is deleted. First we calculate the 2s- and 2p-orbitals in this model. Second, by taking account of K_2s2p in this model, effects of this term on the 2p-orbitals in the ^1,3P states are investigated. In this manner, an explanation is given for the following facts which are obtained from a minimal Slater-type orbital set; (1) for Be and B⁺, the 2p-orbital of the ¹P state is broader than that of the ³P state; (2) for C²⁺, the extension of the 2p-orbital in the two states is almost the same; (3) for O⁴⁺ and Ne⁶⁺, in contrast to Be and B⁺, the 2p-orbital of the ¹P state is tighter than that of the ³P state.     

Accurate lifetime measurements of the 2p 3d 1 D 0 and 2p 3d 3 P 2 0 levels in N II with the beam-foil-laser method

We have obtained accurate values for the radiative lifetimes of the 2p 3d ¹ D ⁰ and 2p 3d ³ P ₂ ^o levels in NII by the cascade-free beam-foil-laser spectroscopy method. Our results are (2p 3d ¹ D ⁰)=0.346±0.012 ns and (2p 3d ³ P ₂ ^o )=0.457±0.020 ns. Comparison of these results with experimental and recent theoretical lifetimes reported previously is also made.Senior Research Associate of the Belgian FNRS     

Laser-Rf double-resonance measurements of the metastable 3d 34s 5P1,2,3, 3d 24s 2 1 G 4 states of 47Ti

The hyperfine structure (hfs) of 4 metastable states of ⁴⁷Ti has been measured very precisely by a laser-rf double resonance method. The corresponding hyperfine structure constants A _exp and B _exp have supplied a set of experimental data necessary for hyperfine structure analysis and determination of Sternheimer free nuclear quadrupole moment Q.     

Characterization of a shallow-bound 0g+ valence state of I2 using emission from the D 0u+(3P2) and F' 0u+(1D2) ion-pair states populated by amplified spontaneous emission

A range of vibrational levels of the D 0(u)(+)((3)P(2)) and F' 0(u)(+)((1)D(2)) ion-pair states of I(2) is shown to be easily generated by amplified spontaneous emission (ASE) from their more accessible partners, E 0(g)(+)((3)P(2)) and f' 0(g)(+)((1)D(2)), in sufficient concentration for dispersed fluorescence studies of the D 0(u)(+)((3)P(2)) --> 0(g)(+)(bb) and F' 0(u)(+)((1)D(2)) --> 0(g)(+)(bb) transitions to be carried out. T(0) (J = 49) of this shallow-bound 0(g)(+)(bb) valence state is unambiguously determined and an improved R(e) value of 3.952 +/- 0.005 A is obtained from optimizing the fit of the intensities of the vibrational progressions in the 0(g)(+)(bb) state, and T(e) is found to be 27311.3 +/- 2 cm(-1), leading to D(e) = 442.0 +/- 2 cm(-1).     

Direct transitions among atomic states of negative reflection symmetry in the scattering plane: Li(2P 0, 3p 0, 3d ±1)-He collisions

This paper reports coupled channel model calculations of direct transitions in Li-He collisions among excited Li-states of negative reflection symmetry in the scattering plane. Using the natural coordinate frame, transition probabilities and orientation and alignment parameters are predicted as functions of impact energy and impact parameter for various initial states. It is found that for geometrical reasons transition probabilities are one to two orders of magnitude smaller than for corresponding states with positive reflection symmetry. Some experimental consequences of this finding are pointed out.     

Electric-field-induced g/u mixing of the E0g+(3P2) and D0u+(3P2) ion-pair states of jet-cooled I2 observed using optical triple resonance

Electric-field-induced electronic state g/u mixing of nearly isoenergetic rovibrational levels of the E0g+(3P2) and D0u+(3P2) ion-pair states of I2 has been observed using optical triple resonance combined with resonance ionization. Detectable mixing with applied fields of 1 kV/cm occurs over a range of energy level separations of < or = 0.3 cm(-1).     

Thermal energy collisions between metastable Ne⋆(2p 53s,3 P 0, 2) and H2(X,1Σ g + )

A crossed beam experiment is used to investigate the Ne*(2p ⁵ 3s,³ P _{0, 2}) ? H₂(¹Σ _g ⁺ ) collision at thermal energy (67 meV). The H₂ beam is supersonic, the Ne* beam is thermal. Different collision processes have been analyzed separately by means of a double chopping technique combined with a time of flight measurement. Ions produced by Penning effect and chemi-ionization have been separated from scattered metastable atoms by an accelerating electric field small enough to preserve a reasonable angular resolution: δ?(ions)=±5.5°, δ?(Ne*)=±1°, which allows a determination of differential cross sections. The attenuation method, combined with an absolute measurement of the total H₂ flux, has been used to measure the total cross section: σ _t =940±220a ₀ ² . Differential cross sections have been obtained, in arbitrary but unique unit, for the following processes: (1) elastic collisions, for a mixture (1:3) of para- and ortho-hydrogen; (2) rotationally inelastic collisions:J=0→2; (3) Penning ionization resulting into H ₂ ⁺ ions; (4) chemiionization yielding NeH⁺ ions.     

Efficient long-range collisional energy transfer between the E0(g)(+)(3P2) and D0(u)(+)(3P2) ion-pair states of I2, induced by H2O, observed using high-resolution Fourier transform emission spectroscopy

Using high-resolution Fourier transform emission techniques, we have resolved rotational structure in the D0(u)(+)((3)P(2)) → X0(g)(+) emission following collisional transfer from the E0(g)(+)((3)P(2)) state in I(2). The P:R branch ratios in the E0(g)(+)((3)P(2)) → D0(u)(+)((3)P(2)) transfer are found to vary enormously with v(E) and v(D). We show that the observed intensities are all consistent with the transfer being dominated by long-range, near-resonant collisions with residual H(2)O. Unequal P:R branch ratios in the E0(g)(+)((3)P(2)) → A1(u) emission have been shown to result from mixing of the E0(g)(+)((3)P(2)) and β1(g)((3)P(2)) states via Ω-uncoupling.     

Quantal close-coupling calculation of the cross sections for the j 1 m 1 → j 2 m 2 transitions in the 4p 2P and 3d 2D excited states of Ca+ induced by collisions with helium

Cross sections for the j ₁ m ₁ → j ₂ m ₂ transitions in the resonance 4p ²P and metastable 3d ²D states of the singly charged calcium ion induced by collisions with the ground-state He atom have been calculated using the quantal close-coupling method. The calculations are based on the earlier obtained Ca⁺-He pseudopotential SCF potential energy curves. The calculated cross sections are discussed in the energy range from threshold to 1.5 eV. Satisfactory agreement with other theoretical results has been found for the 4p ²P state. However, relatively large discrepancy between theory and available experimental data still exists for both the Ca⁺ states.