Electric Octupole Transition Research Articles

Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States inAr+

A laser probing investigation has yielded the lifetimes of the 3s(2)3p(4)(1D)3d (2)G(7/2,9/2) metastable doublet states of Ar+. The results, obtained with the CRYRING ion storage ring of Stockholm, are 3.0+/-0.4 and 2.1+/-0.1 s, respectively. Comparisons with theoretical values calculated with two independent theoretical approaches, i.e., the pseudorelativistic Hartree-Fock method and the multiconfiguration Breit-Pauli approach, have allowed us to establish the unexpected and extraordinary strong contribution of an electric octupole (E3) transition to the ground state, in addition to the M1 decay channels to the 3d ;{2,4}F states and the E2 contributions to the 4s 2P, 2D states.

Generalized oscillator strengths for some higher valence-shell excitations of argon

The valence shell excitations of argon were investigated by an angle-resolved fast-electron energy-loss spectrometer at an incident electron energy of $2500\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, and the transition multipolarities for the excitations of $3p\ensuremath{\rightarrow}3d$, $4d$, $5s$, and $5p$ were elucidated with the help of the calculated intermediate coupling coefficients using the COWAN code. The generalized oscillator strengths for the excitations to $3{p}^{5}(3d,3{d}^{\ensuremath{'}})$, $3{p}^{5}(5p,5{p}^{\ensuremath{'}})$, and $3{p}^{5}(5s,4d)$ were measured, and the profiles of these generalized oscillator strength were analyzed. Furthermore, although the present experimental positions of the maxima for the electric-monopole and electric-quadrupole excitations in $3p\ensuremath{\rightarrow}5p$ are in agreement with the theoretical calculations [Amusia et al., Phys. Rev. A 67, 022703 (2003)], the generalized oscillator strength profiles show obvious differences. In addition, the experimental generalized oscillator strength ratios for the electric-octupole transitions in $3p\ensuremath{\rightarrow}3d$ are different from the theoretical prediction calculated by the COWAN code.

Energy levels and radiative rates for inner shell transitions of Fe XVI

Aims. In this paper we report calculations for energy levels and radiative rates for transitions in Fe xvi. Methods. The General purpose Relativistic Atomic Structure Package (grasp) has been adopted for the calculations of energy levels and radiative rates. Results. Energies for the lowest 134 levels among the (1s 2 2s 2 ) 2p 6 3$\ell$, 2p 5 3s 2 , 2p 5 3s3p, 2p 5 3s3d, 2p 5 3p3d, and 2p 5 3p 2 configurations of Fe xvi are reported. Additionally, radiative rates, oscillator strengths, and line strengths are reported for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), magnetic quadrupole (M2), and electric octupole (E3) transitions among these levels. Comparisons are made with the available results in the literature, and the accuracy of the present results is assessed. Finally, lifetimes for all excited levels are also listed, although no measurements are presently available with which to compare these.

Possible alternative parity bands in the heaviest nuclei

The low-lying alternative parity bands in heaviest nuclei are predicted for the first time. The parity splitting and electric dipole, quadrupole, and octupole transition moments of heavy nuclei are calculated within a cluster model. The model is based on the assumption that reflection asymmetric shapes are produced by the motion of the nuclear system in the mass asymmetry coordinate.

Atomic data from the iron project

Radiative decay rates (A) and line strengths (S ) are presented for a large number of electric dipole allowed (E1) and forbidden electric quadrupole (E2), octupole (E3) and magnetic dipole (M1) transitions in Fe IV. The ion is amongst the most complex iron ions and exhibits effects of strong electron correlation. It has closely spaced fine structure levels from seven configurations: 3s 2 3p 6 3d 5 ,3 s 2 3p 6 3d 4 4s, 3s 2 3p 6 3d 4 4p, 3s 2 3p 6 3d 4 4d, 3s 2 3p 6 3d 3 4s4p, 3s 2 3p 6 3d 3 4s4d, 3s 2 3p 5 3d 6 before an energy gap could be noted. Atomic parameters are presented for multipole radiative transitions among the 1275 fine structure levels dominated by these seven configurations. A total of approximately 173 000 transitions of type E1, E2, E3 and M1 are presented, The set of intercombination and forbidden transitions complements the earlier extensive set of dipole allowed (∆J = 0, ±1, ∆L = 0, ±1, and ∆S = 0) fine structure transitions in Fe IV. The results are obtained in the relativistic Breit-Pauli approximation using an updated atomic structure code SUPERSTRUCTURE. Transition probabilities are compared with the existing results and varying degrees of agreement are found. The total number of transitions presented should provide a reasonably complete set for modeling of most optical to ultraviolet Fe IV spectra of astrophysical sources.

Systematic frequency shifts of the 467 nm electric octupole transition in 171Yb+

The 2S1/2 (F = 0) →2F7/2 (F = 3, mF = 0)transition at 467 nm in a single trapped, laser-cooled ion of 171Yb+has the potential to be an extremely accurate optical frequency reference. Thesystematic shifts of the transition frequency currently make a significantcontribution to the uncertainty on absolute frequency measurements of thetransition. Here the systematic shifts of a recent absolute frequency measurementusing a femtosecond laser frequency comb generator are evaluated, andrealistic limits for the ultimate performance of the standard are estimated.

Kilohertz-resolution spectroscopy of the2S1/2−2F7/2electric octupole transition in a single171Yb+ion

Spectroscopy has been performed on $\mathrm{the}{}^{2}{S}_{1/2}(F=0,{m}_{F}{=0)\ensuremath{-}}^{2}{F}_{7/2}{(F=3,m}_{F}=0)$ electric octupole transition in ${}^{171}{\mathrm{Yb}}^{+}$ with kilohertz resolution. A quantum jump rate of more than one per second has been achieved, a factor of 100 improvement on previous work. Spectra including the sidebands at the trap secular frequency show the ion to be in the Lambe-Dicke regime and hence the Doppler effect has been eliminated to first order. The dynamic Stark shift is a significant perturbation to the frequency because of the high intensity required to drive the octupole transition. It has been measured as ${42}_{\ensuremath{-}10}^{+12} \ensuremath{\mu}\mathrm{Hz}{\mathrm{W}}^{\ensuremath{-}1}{\mathrm{m}}^{2}$ and with further reduction in the probe laser linewidth, it should be possible to reduce the relative uncertainty in this shift to the parts in ${10}^{18}$ level. The transition is free from the Zeeman effect to first order and has a measured second-order shift of $1.9(3) \mathrm{mHz}(\ensuremath{\mu}\mathrm{T}{)}^{\ensuremath{-}2}.$ It should be possible to reduce the relative uncertainty in this shift to below the part in ${10}^{18}$ level. The electric quadrupole shift may be the limiting systematic effect, but cannot yet be observed with the current resolution on the transition.

REDUCED ELECTRIC-OCTUPOLE TRANSITION PROBABILITIES, B(E3;01+→31−)—AN UPDATE

A previous compilation of excitation energies Ex (31−) and reduced electric-octupole transition probabilities B(E3;01+→31−) for first 3− states of even-even nuclides, which covered the literature to March 1988, has been updated to cover the literature to the end of 2000. Data obtained from various experimental procedures are tabulated. The final table presents adopted values of B(E3;01+→31−), together with the E3 transition strengths |M(E3)|2 in Weisskopf units. Plots of |M(E3)|2 versus mass number A, atomic number Z, and neutron number N confirm the existence of structure suggested in the earlier work.

Observation of the2S1/2−2F7/2electric octupole transition in a single171Yb+ion

The ${}^{2}{S}_{1/2}{(F=0)\ensuremath{-}}^{2}{F}_{7/2}(F=3)$ electric octupole transition in ${}^{171}{\mathrm{Yb}}^{+}$ has been detected by observing quantum jumps in the fluorescence of a single ion held in an electrodynamic trap. The transition frequency has been measured as 642 121 498.1 (0.8) MHz. The extreme weakness of this transition makes it ideally suited as an optical frequency reference of subhertz linewidth. The absolute frequencies of a series of Doppler-free absorptions in tellurium vapor are also reported. One of these absorptions was used as a local frequency reference while locating the electric octupole transition.

Measurement of the infrared2F7/2−2D5/2transition in a single171Yb+ion

The ${}^{2}{F}_{7/2}(F=3){--}^{2}{D}_{5/2}(F=2)$ 3.43-\ensuremath{\mu}m transition in ${}^{171}{\mathrm{Yb}}^{+}$ has been measured to be 87 366 282 258(91) kHz. This transition is of interest as an infrared frequency standard. A subsidiary measurement of the 3.43-\ensuremath{\mu}m ${(F=4\ensuremath{-}F}^{\ensuremath{'}}=3)$ transition yields a frequency of 87 362 471 500(800) kHz. Taken with a previous measurement of the ${}^{2}{D}_{5/2}$ level hyperfine splitting, a ${}^{2}{F}_{7/2}$ level hyperfine splitting of 3620(2) MHz and an A factor of 905.0(0.5) MHz are deduced. In addition, a 3.43-\ensuremath{\mu}m transition isotope shift of ${v}_{171}--{v}_{172}=+4048(4)\mathrm{MHz}$ is obtained from these experiments and a known value for the transition in the 172 isotope. These measurements taken with previous work give a value for the ${}^{2}{S}_{1/2}(F=0){--}^{2}{F}_{7/2}(F=3)$ electric octupole transition of 642 121 497 308(178) kHz, which will be used as a starting point in the search for this extremely weak transition.

Observation of an Electric Octupole Transition in a Single Ion

The $^{2}S_{1/2}\ensuremath{-}^{2}F_{7/2}$ electric octupole $(E3)$ transition in ${}^{172}{\mathrm{Yb}}^{+}$ has been detected by observing quantum jumps in a single laser cooled ion, stored in an electrodynamic trap. The transition frequency is 642 116 785.3(0.7) MHz $(1\ensuremath{\sigma})$. Consideration of the transition rate and laser parameters implies a $^{2}F_{7/2}$ level lifetime of 3700 days. This is the first time an atomic $E3$ transition has been driven. This transition has applications as an optical frequency reference.

Probabilities for forbidden transitions in atoms and ions: 1989-1995. A commented bibliography

A list is given of references concerning calculated and measured probabilities for forbidden transitions in atoms and ions. The selection is restricted to electric quadrupole (E2), magnetic dipole (M1), magnetic quadrupole (M2) and magnetic octupole (M3) transitions. In particular, spin-forbidden, hyperfine-structure induced and multiphoton transitions are not considered here. Some comments are included on important aspects of recent work in the field. The period covered goes from 1989 to mid-1995. This paper is thus a complement to our previous bibliography on the subject for the period 1968-1989 [Biémont, E. and Zeippen, C. J., J. de Physique IV, C1, 209 (1991)].

Electron-impact excitation of electric octupole transitions in positive ions: Asymptotic behavior of the sum over partial-collision strengths.

An investigation has been made, for the case of octupole transitions, of the dependence of the partial-collision strength on the orbital angular momentum of the colliding electron. It is shown that, similar to the dipole and quadrupole transitions, the sum over partial-collision strengths is asymptotic to a geometric series of common ratio ${\mathit{E}}_{\mathit{j}}$/${\mathit{E}}_{\mathit{i}}$, where ${\mathit{E}}_{\mathit{i}}$ and ${\mathit{E}}_{\mathit{j}}$ are the initial and final energies of the colliding electron, respectively. For large incident energies (${\mathit{E}}_{\mathit{j}}$/${\mathit{E}}_{\mathit{i}}$\ensuremath{\sim}1) the convergence of the sum to the geometric series is rather slow, since the geometric-series method only starts to become valid for large values of angular momentum. This difficulty is overcome by developing an alternative method in which the approximation is made that ${\mathit{E}}_{\mathit{j}}$/${\mathit{E}}_{\mathit{i}}$=1. An analytic formula is then obtained to estimate the contribution to the total-collision strength from large values of angular momentum. Results of partial- and total-collision strengths are presented for direct electric octupole transitions in ${\mathrm{Ca}}^{+}$ and ${\mathrm{Sr}}^{+}$.

Measurement of Reduced Electric Octupole Transition Probabilities, B(E3; 01??..31), for 118,120,122Sn

Values of reduced electric octupole transition probabilities, B(E3; ot -31), for the nuclides llB,120,122Sn have been determined using Coulomb excitation with 12C projectiles. The results are in good agreement with shell-model calculations made without introducing effective charges but involving core excitations. Values for B(E2; ot -2t) are also presented.

Enhanced octupole collectivity at double subshell closure in the96Zr region

A value of 84 ± 44 ps has been established for the half-life of the first 3− state of96Zr, using the centroid shift method. It is shown that the corresponding large electric octupole transition strength is in accordance with systematics, suggesting largest octupole collectivity when both the 1g9/2 Proton and 1h11/2 neutron orbitals are nearly empty due to the Z=40, N=56 double subshell closure.

High-resolution inelastic electron scattering fromO17

Excited states of $^{17}\mathrm{O}$ up to an excitation energy of 15 MeV have been studied by high-resolution electron scattering for momentum transfers between 0.8 and 2.6 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$. Previous electron-scattering measurements in this excitation region were confined to momentum transfers below 1.1 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$ and were of lower resolution. Form factors were measured and reduced transition probabilities determined for most excited states below 9.5 MeV. The present data are interpreted within the framework of weak-coupling models to facilitate a simple description of the observed spectrum. Particular emphasis is placed upon understanding states that are excited strongly by electric quadrupole or octupole transitions. Spins and parities have been assigned for several levels that have very narrow widths and, hence, are not amenable to partial-wave analyses involving the $^{16}$O+n and $^{13}$C+\ensuremath{\alpha} reactions. Levels at 5.87 MeV (${(3/2}^{+}$), 6.86 MeV (${(5/2}^{+}$), 7.58 MeV (${(7/2}^{+}$), and 8.47 MeV (${(9/2}^{+}$) are suggested as candidates for predominantly 5p-4h members of a ${K}^{\ensuremath{\pi}}$${=(3/2}^{+}$ rotational band. A narrow state (\ensuremath{\Gamma}\ensuremath{\le}20 keV) at 12.22\ifmmode\pm\else\textpm\fi{}0.02 MeV was observed for the first time and the existence of narrow states at 8.90\ifmmode\pm\else\textpm\fi{}0.02 and 14.72\ifmmode\pm\else\textpm\fi{}0.02 MeV was confirmed.

Generalized oscillator strength for the transition [formula omitted]1B 2u ← [formula omitted]1A 1g in benzene at initial kinetic energies 400 eV and 500 eV

Generalized oscillator strengths, ƒ, for the transition A 1B 2u ← X 1A 1g in benzene, determined by electron impact methods, are reported as a function of the momentum change. At scattering angles down to 2.5° helium was used as the comparison gas. Determinations are also reported at θ = 0° using mercury as the comparison gas. The oscillator strength curve has both a minimum and a maximum due to the superposition of electric dipole and octupole transitions. The band envelope is studied and is shown to remain unchanged in shape but is shifted by hν 6 ≈ 0.065 eV with increasing angle due to the shift from electric dipole to octupole scattering.

Simple two-level model of the hole-vibration quadruplet in 39K

The 3 2 − (3.02) , 5 2 − (3.88) , 7 2 − (2.82, 4.13) and 9 2 − (3.60 MeV) levels in 39K are described in a simple two-level model consisting of (i) a d 3 2 −1 proton hole coupled to the 3 − vibration in 40Ca and (ii) the dominating two-hole, one-particle shell-model configuration. Reasonable agreement with experimental energies and electric octupole transition strengths is obtained.

Magnetic quadrupole transitions in X-ray spectra

In continuation of the classification of forbidden transitions in x-ray spectra made by Padalia and Rao in 1969, some of the reported transitions in x-ray spectra have been classified as an admixture of electric octupole and magnetic quadrupole transitions.

A simplified treatment of octupole vibrations in deformed heavy nuclei

Some collective properties of nuclei belonging to the rare-earth and transuranic regions are described within the framework of the quasi-particle random phase approximation utilizing a pairing plus a state-independent octupole force model. Energies corresponding to the K = 0, 1, 2 and 3 octupole vibrational band heads and reduced electric octupole transitions to these bands are calculated. The results thus obtained are compared to the predictions given by the pairing plus octupole force and by the surface delta interaction. It is found that the extremely simple model proposed in this paper gives as good agreement with experiment as the other two models do.