We present experimental atomic lifetimes for 12 levels in Sb I, out of which seven are reported for the first time. The levels belong to the 5p$^2$($^3$P)6s $^{2}$P, $^{4}$P and 5p$^2$($^3$P)5d $^{4}$P, $^{4}$F and $^{2}$F terms. The lifetimes were measured using time-resolved laser-induced fluorescence. In addition, we report new calculations of transition probabilities in Sb I using a Multiconfigurational Dirac-Hartree-Fock method. The physical model being tested through comparisons between theoretical and experimental lifetimes for 5d and 6s levels. The lifetimes of the 5d $^4$F$_{3/2, 5/2, 7/2}$ levels (19.5, 7.8 and 54 ns, respectively) depend strongly on the $J$-value. This is explained by different degrees of level mixing for the different levels in the $^4$F term.
Electric quadrupole (E2) and magnetic dipole (M1) transition amplitudes among the low-lying states of quadruply ionized vanadium V$^{4+}$, important in various field of experimental and astrophysics are presented very accurately. Most of these results are reported for the first time in the literature. Relativistic coupled-cluster theory with single, double and leading triple excitations has been employed for these calculations. Estimation of different correlation effects arising through the above formalism have been highlighted by studying core and valence electrons excitations to the excited …
We report lifetime measurements of the 6 levels in the 3d6(5D)4d e6G term in Fe ii at an energy of 10.4 eV, and f -values for 14 transitions from the investigated levels. The lifetimes were measured using time-resolved laser-induced fluorescence on ions in a laser-produced plasma. The high excitation energy, and the fact that the levels have the same parity as the the low-lying states directly populated in the plasma, necessitated the use of a two-photon excitation scheme. The probability for this process is greatly enhanced by the presence of the 3d6(5D)4p z6F levels at roughly half the energ…
We have investigated energies, magnetic dipole hyperfine structure constants ($A_{hyf}$) and electric dipole (E1) matrix elements of a number of low-lying states of the triply ionized tin (Sn$^{3+}$) by employing relativistic coupled-cluster theory. Contributions from the Breit interaction and lower-order quantum electrodynamics (QED) effects in determination of above quantities are also given explicitly. These higher-order relativistic effects are found to be important for accurate evaluation of energies, while QED contributions are seen to be contributing significantly to the determination o…
Argon energies of J=1 odd and J=2 even states, oscillator strengths of the two lowest J=1 odd states, and line strengths for transitions between J=1 odd and J=2 even excited states are calculated with the CI+MBPT method. The results are in good agreement with experiment.
Recently the lifetime of the excited $^{2}P_{1/2}$-state of S$^-$ was measured to be $503\pm 54$ s (Bäckström et al. Phys. Rev. Lett. 114, 143003 (2015)). The earlier theoretical lifetime of $436$ s was clearly outside the experimental error bars. To investigate this discrepancy we have performed systematic and large-scale multiconfiguration Dirac-Hartree-Fock calculations for this system. After including a careful treatment of correlation and relativistic effects, we predict a well-converged value of $492$ s for this lifetime, with an uncertainty considerably less than 1%, thereby removing th…
The 6s-np_j (n=6-9) electric-dipole matrix elements and 6s-nd_j (n=5-7) electric-quadrupole matrix elements in Ba+ are calculated using the relativistic all-order method. The resulting values are used to evaluate ground state dipole and quadrupole polarizabilities. In addition, the electric-dipole 6p_j-5d_j' matrix elements and magnetic-dipole 5d_{5/2}-5d_{3/2} matrix element are calculated using the same method in order to determine the lifetimes of the 6p_{1/2}, 6p_{3/2}, 5d_{3/2}, and 5d_{5/2} levels. The accuracy of the 6s-5d_j matrix elements is investigated in detail in order to estimate…
The atomic states of the W IX (W8+) tungsten ion lying below the W9+ ionisation threshold have been studied theoretically, employing the multiconfiguration Dirac-Hartree-Fock method with configuration interaction. The level electronic structures and their energies are presented. The electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) radiative transitions have been computed in order to calculate the radiative lifetimes of given states. Transition wavelengths, energies, and decay rates are also presented for selected high-intensity E1 transitions. …
The lifetimes of the $6d \ ^2D_{3/2}$ and $6d \ ^2D_{5/2}$ states in Fr are estimated to be 540(10) ns and 1704(32) ns respectively. They are determined by calculating the radiative transition amplitudes of the allowed electric dipole (E1) and the forbidden electric quadrupole (E2) and magnetic dipole (M1) channels using the second order many-body perturbation theory (MBPT(2)) and the coupled-cluster (CC) method at different levels of approximation in the relativistic framework. These long lifetimes and the large electric dipole parity non conserving amplitudes of $7s \ ^2S_{1/2} \rightarrow 6…
In this comment, through our independent calculations, we assess that the recently reported results of El-Maaref et al. [{\em Indian J. Phys.} {\bf 91} 1029 (2017)] for energy levels, oscillator strengths, radiative rates, and lifetimes are inaccurate and unreliable for several levels and transitions of S-like Sc~VI.
This work is an ab initio study of the 2p3 4So_3/2, and 2Do_{3/2,5/2} states of C- and 2p2 3P_{0,1,2}, 1D_2, and 1S_0 states of neutral carbon. We use the multi-configuration Hartree-Fock approach, focusing on the accuracy of the wave function itself. We obtain all C- detachment thresholds, including correlation effects to about 0.5%. Isotope shifts and hyperfine structures are calculated. The achieved accuracy of the latter is of the order of 0.1 MHz. Intra-configuration transition probabilities are also estimated.
The ground state hyperfine splitting values and the transition probabilities between the hyperfine structure components of high Z lithiumlike ions are calculated in the range $Z=49-83$. The relativistic, nuclear, QED and interelectronic interaction corrections are taken into account. It is found that the Bohr-Weisskopf effect can be eliminated in a combination of the hyperfine splitting values of the hydrogenlike and lithiumlike ions of an isotope. This gives a possibility for testing the QED effects in a combination of the strong electric and magnetic fields of the heavy nucleus. Using the ex…
Relativistic coupled-cluster (RCC) calculations have been performed to estimate the electromagnetic forbidden transition probabilities, oscillator strengths and lifetimes of many low-lying states of five times ionized molybdenum (Mo VI). Contributions from the Breit interaction up to the first order of perturbation have been examined. Our results are in good agreement with the available other reported theoretical and experimental results. A long lifetime about 4.9854 s of the first excited state, 4d $^2D_{5/2}$, has been predicted which can be a very useful criteria in the doping process of th…
We measure the lifetime of the cesium $5^2D_{5/2}$ state using a time-resolved single-photon-counting method. We excite atoms in a hot vapor cell via an electric quadrupole transition at a wavelength of $685\,\mathrm{nm}$ and record the fluorescence of a cascade decay at a wavelength of $852\,\mathrm{nm}$. We extract a lifetime of $1353(5)\,\mathrm{ns}$ for the $5^2D_{5/2}$ state, in agreement with a recent theoretical prediction. In particular, the observed lifetime is consistent with the literature values of the polarizabilities of the cesium $6P$ states. Our measurement contributes to resol…
This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d8 4d levels of astrophysical interest in singly ionized nickel. Radiative lifetimes of seven high-lying levels of even parity in Ni II (98400 -100600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculat…
Two different theoretical methods have been used to complete a new calculation of polarizability in the thallium 6p_{1/2}, 7s, and 7p_{1/2} states. The predictions of the two methods agree to within 1% for the 6p_{1/2} and 7s states and 2% for 7p_{1/2} state. We find that the theoretical expression for the 6p_{1/2} - 7s transition polarizability difference is dominated (greater than 90% contribution) by mixing of the 7s state with the 7p_{1/2} and 7p_{3/2} states. By comparing the theoretical expression to an existing Stark shift measurement [Doret et al., Phys. Rev. A 66, 052504 (2002)], new,…
Metastable levels in rhodium-like ions with the ground configuration $4p^{6}4d^{9}$ and the excited configurations $4p^{6}4d^{8}4f$ and $4p^{5}4d^{10}$ are investigated. The {\sl ab initio} calculations of the level energies, radiative multipole transition probabilities are performed in a quasirelativistic Hartree-Fock approximation employing an extensive configuration interaction based on quasirelativistic transformed radial orbitals. A systematic trends in behavior of calculated radiative lifetimes of the metastable levels are studied for the ions from $Z=60$ to $Z=92$. The significance of t…
This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions of astrophysical interest in singly ionized cobalt. More precisely, nineteen radiative lifetimes in Co+ have been measured with the time-resolved laser-induced fluorescence technique using one- and two-step excitations. Out of these, seven belonging to the high lying 3d$^7$($^4$F)4d configuration in the energy range 90697 - 93738 cm$^{-1}$ are new, and the other twelve from th3d$^7$($^4$F)F)4p configuration with energies between 45972 and 49328 cm$^{-1}$1 are compared with previous measur…
Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4 3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics (QED) corrections. The results are compared with all existing experimental and theoretical data.
Theoretical transition energies and probabilities for He-, Li- and Be-like Praseodymium ions are calculated in the framework of the multi-configuration Dirac-Fock method (MCDF), including QED corrections. These calculated values are compared to recent experimental data obtained in the Livermore SuperEBIT electron beam ion trap facility.
Lifetimes of the first two metastable states in Sc^{2+} and Y^{2+} are determined using the relativistic coupled-cluster theory. There is a considerable interest in studying the electron correlation effects in these ions as though their electronic configurations are similar to the neutral alkali atoms, their structures are very different from the latter. We have made a comparative study of the correlation trends between the above doubly ionized systems with their corresponding neutral and singly ionized iso-electronic systems. The lifetimes of the excited states of these ions are very importan…
We have realized a one dimensional optical lattice for individual atoms with a lifetime >300 s, which is 5 times longer than previously reported. In order to achieve this long lifetime, it is necessary to laser cool the at-oms briefly every 20 s to overcome heating due to technical fluctuations in the trapping potential. Without cooling, we observe negligible atom loss within the first 20 s followed by an exponential decay with a 62 s time constant. We obtain quantitative agreement with the measured fluctuations of the trapping potential and the corresponding theoretical heating rates.
We have calculated energy levels and lifetimes of 4f7 and 4f6 5d configurations of Gd IV using Hartree-Fock and configuration interaction methods. This allows us to reduce significantly the uncertainty of the theoretical determination of the electron electric dipole moment (EDM) enhancement factor in this ion and, correspondingly, in gadolinium-containing garnets for which such measurements were recently proposed. Our new value for the EDM enhancement factor of Gd+3 is -2.2 +- 0.5. Calculations of energy levels and lifetimes for Eu~III are used to control the accuracy.
We report measurements of the lifetimes of the 3d $^2$D$_{5/2}$ and 3d $^2$D$_{3/2}$ metastable states of a single laser-cooled $^{40}$Ca$^+$ ion in a linear Paul trap. We introduce a new measurement technique based on high-efficiency quantum state detection after coherent excitation to the D$_{5/2}$ state or incoherent shelving in the D$_{3/2}$ state, and subsequent free, unperturbed spontaneous decay. The result for the natural lifetime of the D$_{5/2}$ state of 1168(9) ms agrees excellently with the most precise published value. The lifetime of the D$_{3/2}$ state is measured with a single …
A comprehensive theoretical study of the E1, M1, E2 transitions of Ca-like tungsten ions is presented. Using multi-configuration Dirac-Fock (MCDF) method with a restricted active space treatment, the wavelengths and probabilities of the M1 and E2 transitions between the multiplets of the ground state configuration ([Ne]3s$^{2}$3p$^{6}$3d$^{2}$) and of the E1 transitions between [Ne]3s$^{2}$3p$^{5}$3d$^{3}$ and [Ne]3s$^{2}$3p$^{6}$3d$^{2}$ have been calculated. The results are in reasonable agreement with available experimental data. The present E1 and M1 calculations are compared with previous…
The astrophysically important electric quadrupole (E2) and magnetic dipole (M1) transitions for the low-lying states of triply ionized titanium (Ti IV) are calculated very accurately using a state-of-art all-order many-body theory called Coupled Cluster (CC) theory in the relativistic frame-work. Different many-body correlations of the CC theory has been estimated by studying the core and valence electron excitations to the unoccupied states. The calculated excitation energies of different states are in very good agreement with the measurements. Also we compare our calculated electric dipole (…
Tiny radiative losses below the 0.1% level can prove ruinous to the effective laser cooling of a molecule. In this paper the laser cooling of a hydride is studied with rovibronic detail using ab initio quantum chemistry in order to document the decays to all possible electronic states (not just the vibrational branching within a single electronic transition) and to identify the most populated final quantum states. The effect of spin-orbit and associated couplings on the properties of the lowest excited states of BaH are analysed in detail. The lifetimes of the A$^2Π_{1/2}$, H$^2Δ_{3/2}$ and E$…
We find very good agreement between our theoretically evaluated lifetimes of the $5d \ ^2D_{3/2}$ and $5d \ ^2D_{5/2}$ states of Cs with the experimental values reported in [Phys. Rev. A {\bf 57}, 4204 (1998)], which were earlier evinced to be disagreeing with an earlier rigorous theoretical study [Phys. Rev. A {\bf 69}, 040501(R) (2004)] and with another precise measurement [Opt. Lett. {\bf 21}, 74 (1996)]. In this work, we have carried out calculations of the radiative transition matrix elements using many variants of relativistic many-body methods, mainly in the coupled-cluster theory frame…
Lifetime measurements using beam foil techniques for the $5s5p^{2}$ $^{2}D_{3/2,5/2}$ levels in Sn II are presented. The resulting oscillator strengths for transitions at 1699.4, 1831.8 and 1811.2 Å are reported. We also studied these levels with multi-configuration Dirac Hartree-Fock (MCDHF) calculations using a development version of the GRASP2K package. Our experimental and theoretical results are compared with other available studies.
We present lifetime measurements using beam-foil techniques for radiative transitions from the 3$p^4$($^1S$)4$s$ $^2S_{1/2}$, 3$p^4$($^3P$)5$s$ $^2P_{1/2,3/2}$, and 3$p^4$($^3P$)3$d$ $^2F_{5/2}$ levels in Cl I and the corresponding results of the oscillator strengths for transitions at 1004.68, 1079.88, 1090.73, and 1094.77 Å, respectively. We compare our experimental results with available theoretical calculations and astronomical observations in an effort to resolve discrepancies among them.
We report lifetimes, branching fractions, and the resulting oscillator strengths for transitions within the P II multiplet (3s23p2 3P - 3s3p3 3Po) at 1308 Å. These comprehensive beam-foil measurements, which are the most precise set currently available experimentally, resolve discrepancies involving earlier experimental and theoretical results. Interstellar phosphorus abundances derived from λ1308 can now be interpreted with greater confidence. In the course of our measurements, we also obtained an experimental lifetime for the 3p4s 3P0o level of P IV. This lifetime agrees well with the availa…
We present a combined experimental and theoretical study on the radiative lifetime of CO in the $a^3Π_{1,2}, v=0$ state. CO molecules in a beam are prepared in selected rotational levels of this metastable state, Stark-decelerated and electrostatically trapped. From the phosphorescence decay in the trap, the radiative lifetime is measured to be $2.63\pm0.03$ ms for the $a^3Π_1, v=0, J=1$ level. From spin-orbit coupling between the $a^3Π$ and the $A^1Π$ state a 20% longer radiative lifetime of 3.16 ms is calculated for this level. It is concluded that coupling to other $^1Π$ states contributes …
