2s2p 1P Research Articles

Absolute frequency measurement of the 5s5p 1P1 - 5s5d 1D2 transition in strontium

We report on the absolute frequency determination of the 5s5p 1P1 - 5s5d 1D2 transition in atomic strontium, achieved through frequency comb-referenced laser-induced-fluorescence (LIF) spectroscopy. We excite the 5s21S0 - 5s5p 1P1 transition using an on-resonance laser at ≈461 nm, and then measure the variation in the LIF signal while scanning the laser at ≈767 nm across the 5s5p 1P1 - 5s5d 1D2 transition. We determine the absolute frequency of 390599571.7±0.4 MHz, with an accuracy that surpasses the previous most accurate measurement by two orders of magnitude. This measurement technique can be readily applied for precision spectroscopy of high-lying states not only in strontium, but also in other atomic species.

Effect of dense plasma environment and external magnetic field on atomic structure and radiative properties of Ar XVII

Atomic structures and radiative properties of He like Ar XVII in the presence of dense plasma environments and external magnetic field have been presented within the framework of the relativistic theory. For this purpose, the relativistic configuration interaction method by incorporating the generalized b-potential and external magnetic field has been implemented. Plasma screening effect on 1s2 1S0 → 1s2p 3P1 transitions of Ar XVII ion in the presence of an external magnetic field has been investigated. We also studied the Zeeman splitted energies and predicted the excitation energies of Ar XVII ion for the magnetic sublevels 1s2p 3P0 (MJ = 0), 3P1 (MJ = 0, ±1), 3P2 (MJ = 0, ±1, ±2), 1P1 (MJ =0, ±1). Our calculated results are in excellent agreement with National Institute of Science and Technology (NIST) database and other theoretical available data.

Investigating the Impact of Atomic Data Uncertainties on the Measured Physical Parameters of the Perseus Galaxy Cluster

Accurate atomic data and plasma models are essential for interpreting the upcoming high-quality spectra from missions like XRISM and Athena. Estimating physical quantities, like temperature, abundance, turbulence, and the resonance scattering factor, is highly dependent on the underlying atomic data. We use the AtomDB tool variableapec to estimate the impact of atomic data uncertainties in Einstein A coefficients, collisional rate coefficients, and the ionization and recombination rates of H-, He-, and Li-like iron in modeling the spectrum of Perseus observed by Hitomi. The best-fit temperatures, abundances, resonance scattering factors, and turbulence parameters including atomic data uncertainties vary by approximately 17%, 35%, 30%, and 3%, respectively, from the best-fit temperatures, abundances, RS factors, and turbulence parameters estimated without atomic data uncertainties. These indicate that approximately 32%, 35%, and 25% of the best-fit temperatures, abundances, and resonance scattering factors when including uncertainties lie outside the 3σ error regions of their corresponding best-fit values computed with zero atomic data errors. Expanding the energy range to 1.8–20.0 keV shows less variability, with 26% of the abundances and 22% of the resonance scattering factors lying outside the 3σ errors of the best-fit values. We also studied correlations between physical parameters and atomic rate uncertainties to identify key atomic quantities requiring precise lab measurements. We report negative correlations between the best-fit temperatures and the z (1s2s 3S1 → 1s2) collisional rate coefficients, abundances and y (1s2p 3P1 → 1s2) collisional rate coefficients, and abundances and z collisional rate coefficients, and a positive correlation between the resonance scattering factors and the w (1s2p 1P1 → 1s2) collisional rate coefficients.

Modeling the Mg I from the NUV to MIR

Context. Reliable atomic data are mandatory ingredients to obtain a realistic semiempirical model of any stellar atmosphere. Due to their importance, we further improved our recently published Mg I atomic model. Aims. We tested the new atomic model using atmospheric models of stars of different spectral types: the Sun (dG2), HD 22049 (dK2, Epsilon Eridani), GJ 832 (dM2), and GJ 581 (dM3). Methods. Significant improvements have been included in the atomic model, mainly to the electron impact excitation (ϒij) values. We used new Breit-Pauli distorted-wave (DW) multiconfiguration calculations, which proved to be relevant for many transitions in the mid-infrared (MIR) range. The new atomic model of Mg I includes the following: (i) recomputed (ϒij) data through the DW method, including the superlevels. (ii) For the nonlocal thermodynamic equilibrium (NLTE) population calculations, 5676 theoretical transitions were added (3001 term-to-term). (iii) All of these improvements were studied in the Sun and the stars listed above. Comparisons for the distribution of magnesium among the first ionization states and the formation of molecules, as well as for the population of the different energy levels and atmospheric heights, were carried out. Several lines, representative of the spectral ranges, were selected to analyze the changes that were produced. In particular, we exemplify these results with the problematic line 2853.0 Å, a transition between the third level and the ground state. Results. The magnesium distribution between ionization states for stars with different effective temperatures was compared. For the Sun and Epsilon Eridani, Mg II predominates with more than 95%, while for GJ 832 and GJ 581, Mg I represents more than 72% of the population. Moreover, in the latter stars, the amount of magnesium forming molecules in their atmosphere is at least two orders of magnitude higher. Regarding the NLTE population, a noticeable lower variability in the departure coefficients was found, indicating a better population coupling for the new model. Comparing the synthetic spectrum calculated with the older and new Mg I atomic model, these results show minimal differences in the visible range but they are stronger in the infrared (IR) for all of the stars. This aspect should be considered when using lines from this region as indicators. Nevertheless, some changes in the spectral type were found, also emphasizing the need to test the atomic models in different atmospheric conditions. The most noticeable changes occurred in the far-ultraviolet (FUV) and near-ultraviolet (NUV), obtaining a higher flux for the new atomic model regardless of the spectral type. The new model did not prevent the formation of the core emission in the synthetic NUV line 2853.0 Å. However, by including other observations, we could note that the emission indeed exists, although with a much lower intensity. Further tests have shown that to reduce the emission, the population of its upper level (3s3p 1P) should be reduced by a factor of about 100.

Exponentially Correlated Hylleraas–Configuration Interaction Studies of Atomic Systems. III. Upper and Lower Bounds to He-Sequence Oscillator Strengths for the Resonance 1S→1P Transition

The exponentially correlated Hylleraas–configuration interaction method (E-Hy-CI) is a generalization of the Hylleraas–configuration interaction method (Hy-CI) in which the single rij of an Hy-CI wave function is generalized to a form of the generic type rijνije−ωijrij. This work continues the exploration, begun in the first two papers in this series (on the helium atom and on ground and excited S states of Li II), of whether wave functions containing both linear and exponential rij factors converge more rapidly than either one alone. In the present study, we examined not only 1s2 1S states but 1s2p 1P states for the He I, Li II, Be III, C V and O VII members of the He isoelectronic sequence as well. All 1P energies except He I are better than previous results. The wave functions obtained were used to calculate oscillator strengths, including upper and lower bounds, for the He-sequence lowest (resonance) 1S→1P transition. Interpolation techniques were used to make a graphical study of the oscillator strength behavior along the isoelectronic sequence. Comparisons were made with previous experimental and theoretical results. The results of this study are oscillator strengths for the 1s2 1S→ 1s2p1P He isoelectronic sequence with rigorous non-relativistic quantum mechanical upper and lower bounds of (0.001–0.003)% and probable precision ≤ 0.0000003, and were obtained by extending the previously developed E-Hy-CI formalism to include the calculation of transition moments (oscillator strengths).

State-selective Charge Exchange in 19.5–100 keV amu−1 O6+ Collision with He and H2

The cross sections of state-selective charge exchange (CX) between highly charged ions and neutrals are important for modeling extreme ultraviolet and soft X-ray emissions in many astrophysical objects with hot plasma impacting cold media. By using cold-target recoil-ion momentum spectroscopy, we measure O6+ CX collisions with He and H2 in the collision energy range of 19.5 to 100 keV amu−1. The relative cross sections of state-selective single CX are reported for electron capture into O5+(1s 2 nl) n = 2, 3, 4, 5, ≥6 and n = 3, 4, 5, ≥6 for He and H2, respectively. With the collision energy increasing to 100 keV amu−1, the main capture channel shifts to higher n for both target species as compared to available theoretical results. We also report state-selective cross sections for double CX with He, where doubly excited states of with being 2s 2 (1S), 2s2p (1P), 2p 2 (1D), and 2p 2 (1S) [symmetric configurations] and 2s3l, 2p3l−2s4l, and 2s5l−2p5l [asymmetric configurations] are distinguished. It is found that the contributions of doubly excited states with asymmetric configurations are dominant and symmetric configurations increasingly come into play with the increase of collision energy. The present results provide experimental benchmarks available for theoretical calculations.

Frequency measurement of 6s6p 3P0,2−6s7s 3S1 transitions in ultracold 171Yb atoms referenced to local optical clock

We experimentally determine the absolute frequencies and hyperfine splittings of the 6s6p3P0,2 − 6s7s3S1 transitions of ultracold 171Yb atoms in an optical lattice. A frequency comb referenced to an ultrastable optical cavity is used to measure the electric-dipole transition frequencies. With the normalized shelving detection technique, about 12 MHz and 10 MHz linewidth of atomic spectra are obtained, respectively, which is some greater than the natural linewidth of 1.5 MHz and 5.9 MHz and is limited by the broadening from the probe and lattice light. By reference to our 171Yb 6 s2 1S0 − 6s6p3P0 clock, the absolute frequencies are found to be 461861338.03 (0.21) MHz and 461871596.07 (0.31) MHz for the 6s6p3P0 − 6s7s3S1 (F = 1/2 and F = 3/2) transitions, which are more accurate than the previous measurement by one order of magnitude. For the 6s6p3P2 (F = 3/2 and F = 5/2) − 6s7s3S1 (F = 1/2 and F = 3/2) transitions, the measured frequencies are 389257019.71 (0.65) MHz, 389267277.10 (0.37) MHz and 389260569.95 (0.89) MHz, respectively, which are the first measurements to our knowledge. Furthermore, the hyperfine constants for the 6s6p3P2 and 6s7s3S1 states are determined to be 2682.86(0.38) MHz and 6838.69(0.25) MHz, both of which agree well with other recent experimental results.

Continuous outcoupling of ultracold strontium atoms combining three different traps

We have demonstrated the continuous outcoupling of ultracold 88Sr atoms using a moving optical lattice. While Sr atoms are Zeeman-slowed and magneto-optically trapped on the 1S0–1P1 transition, the atoms relaxed to the 5s5p 3P2 metastable state are magnetically trapped and Doppler cooled on the 5s5p 3P2–5s4d 3D3 transition at 2.92 μm. By optically pumping the atoms to the 5s5p 3P0 state, we outcouple the atoms by a moving optical lattice. Such a continuous atomic source enables superradiant lasers and the zero-dead-time operation of atom interferometers and optical lattice clocks.

High Lying Precise Resonance Energies from Photoionization Studies of Se3+ and Rb+ Ions Using the Screening Constant per Unit Nuclear Charge Formalism

Resonance energies of the 4s4p (3P0,1)np, 4s4p (3P2)np (2P3/2, 4D7/2, 4D5/2) and 4s4p (1P1)np (2D3/2, 2D5/2) Rydberg series of Se3+ ions along with resonance energies of the 4s24p5 (2P°1/2) nd1P°1 and 4s4p6 (2S1/2) np 1P°1 series of Rb+ ions are reported. Calculations are done in the framework of the screening constant per unit nuclear charge (SCUNC) formalism. The fine structure splitting of the 4s4p (3P2)np (2P3/2, 4D7/2, 4D5/2) series from n = 10 to n = 27 and for the 4s4p (1P1)np (2D3/2, 2D5/2) series from n = 8 to 11 are resolved in this paper. Very good agreements are obtained between the present calculations and the available experimental and theoretical literature data. The present predicted data up to n = 40 may be of great importance for the atomic physics community in connection with the understanding of the chemical evolution of the Se and Rb elements in the Universe.

Direct loading of Yb atoms into a 3D magneto-optical trap from a dispenser atomic source

The realization of cold atoms using a compact and low-power-consumption experimental setup is indispensable for cold atom experiments, including optical clocks and quantum simulations. We demonstrate the direct loading of Yb atoms into a 3D magneto-optical trap (MOT) from a dispenser atomic source without using a Zeeman slower. The power consumption of the dispenser was ∼3 W. Spectroscopy of the atomic beam from the dispenser on the 6s2 1S0–6s6p 1P1 Yb transition at 399 nm shows that the flux of the atomic beam reaches 1.4 × 1013 s−1 cm−2. We can load up to 4.1 × 107 atoms into the MOT with slowing and trapping laser powers of 20.3 and 35.0 mW, respectively. The realized cold atom system is reliable and can be adapted for experiments on alkaline earth and other alkaline earth-like atoms.

Absolute frequency measurement of the 6s21S0 → 6s6p3P1F = 3/2 → F' = 5/2 201Hg transition with background-free saturation spectroscopy.

We report the development of a method for eliminating background-induced systematic shifts affecting precise measurements of saturation absorption signals. With this technique, we measured the absolute frequency of the 6s21S0 → 6s6p3P1 transition in 201aHg (F = 3/2 → F' = 5/2) to be 1181541111051(83) kHz. The measurement was referenced with an optical frequency comb synchronized to the frequency of the local representation of the UTC. This specific atomic line is situated on the steep slope of the Doppler background at room temperature, which results in a frequency systematic shift. We determined the dependence of this shift on the properties of both the spectral line and the background of the measured signal.

RELATIVISTIC APPROACH TO COMPUTING WAVELENGTHS OF TRANSITIONS IN SPECTRA OF ATOMIC SYSTEMS IN PLASMAS

New relativistic approach to computing the spectral parameters of multicharged ions in plasmas for different values of the plasmas screening (Debye) parameter (respectively, electron density, temperature) is presented. The presented approach is based on the generalized relativistic energy approach combined with the optimized relativistic many-body perturbation theory with the Dirac-Debye screening hamiltonian as a zeroth approximation, adapted for application to study the energy and spectral parameters of atoms and ions in plasmas. The special exchange potential as well as the electron density with dependence upon the temperature are used. The wavelengths for a number of transitions, including (A): E(1s2p 1P1)-E(1s2 1S); (B) E(1s3p 1P1)_E(1s2 1S); (C)AK: E(1s2p 3P1)_E(1s2s 3S); (D): E(1s3p 3P1)_E(1s2s 3S) of the helium in plasmas for various Debye lengths are calculated and compared with the corresponding data by Kar-Ho.

Large-scale Multiconfiguration Dirac–Hartree–Fock Calculations for Astrophysics: C-like Ions from O iii to Mg vii

Large-scale multiconfiguration Dirac–Hartree–Fock calculations are provided for the n ≤ 5 states in C-like ions from O iii to Mg vii. Electron correlation effects are accounted for by using large configuration state function expansions, built from sets of orbitals with principal quantum numbers n ≤ 10. An accurate and complete data set of excitation energies, wavelengths, radiative transition parameters, and lifetimes is offered for the 156 (196, 215, 272, 318) lowest states of the 2s 22p 2, 2s2p 3, 2p 4, 2s 22p3s, 2s 22p3p, 2s 22p3d, 2s2p 23s, 2s2p 23p, 2s2p 23d, 2p 33s, 2p 33p, 2p 33d, 2s 22p4s, 2s 22p4p, 2s 22p4d, 2s 22p4f, 2s2p 24s, 2s2p 24p, 2s2p 24d, 2s2p 24f, 2s 22p5s, 2s 22p5p, 2s 22p5d, 2s 22p5f, and 2s 22p5g configurations in O iii (F iv, Ne v, Na vi, Mg vii). By comparing available experimental wavelengths with the MCDHF results, the previous line identifications for the n = 5, 4, 3 → n = 2 transitions of Na vi in the X-ray and EUV wavelength range are revised. For several previous identifications discrepancies are found, and tentative new (or revised) identifications are proposed. A consistent atomic data set including both energy and transition data with spectroscopic accuracy is provided for the lowest hundreds of states for C-like ions from O iii to Mg vii.

Debye-screening effect on electron-impact excitation of helium-like Al11+ and Fe24+ ions

Debye-screening effects on the electron-impact excitation (EIE) processes for the dipole-allowed transition 1s2 1 S → 1s2p 1P in He-like Al11+ and Fe24+ ions are investigated using the fully relativistic distorted-wave methods with the Debye–Hückel (DH) model potential. Debye-screening effects on the continuum-bound (CB) interaction and target ion are discussed, both of which result in reduction of EIE cross sections. This reduction due to screening on the CB interaction is dominant. The non-spherical and spherical DH potentials are adopted for considering the screening effect on the CB interaction. It is found that the spherical DH potential could significantly overestimate the influence of plasma screening on EIE cross sections for multielectron He-like ions.

Observation of photon recoil effects in single-beam absorption spectroscopy with an ultracold strontium gas

We report on observing photon recoil effects in the absorption of a single monochromatic light at 689 nm through an ultracold 88Sr gas, where the recoil frequency is comparable to natural linewidth of the narrow-line transition 5s2 1S0–5s5p 3P1 in strontium. In the regime of high-saturation, the absorption profile becomes asymmetric due to the photon-recoil shift, which is of the same order as the natural linewidth. The lineshape is described by an extension of the optical Bloch equations including the momentum transfers to atoms during emission and absorption of photons. Our work reveals the photon recoil effects in a simplest single-beam absorption setting, which is of significant relevance to other applications such as saturation spectroscopy, Ramsey interferometry, and absorption imaging.

High power continuous laser at 461 nm based on a compact and high-efficiency frequency-doubling linear cavity.

A Watt-level continuous and single frequency blue laser at 461 nm is obtained by frequency-doubling an amplified diode laser operating at 922 nm via a LBO crystal in a resonant Fabry-Pérot cavity. We achieved a best optical conversion efficiency equal to 87% with more than 1 W output power in the blue, and limited by the available input power. The frequency-converted beam is characterized in terms of long term power stability, residual intensity noise, and geometrical shape. The blue beam has a linewidth of the order of 1 MHz, and we used it to magneto-optically trap 88Sr atoms on the 5s2 1S0 - 5s5p 1P1 transition. The low-finesse, linear-cavity doubling system is very robust, maintains the lock for several days, and is compatible with a tenfold increase of the power levels which could be obtained with fully-fibered amplifiers and large mode area fibers.

Satellite lines of helium-like ions in strongly coupled plasma environment

We report the transition energies and probabilities of satellite lines due to 2p2(3P0,1,2)→1s2p(3P0,1,2) transitions of He-like C,Ne,Al and Ar ions embedded in strongly coupled plasma (SCP) environment. The SCP environment is represented by the ion-sphere (IS) model and the IS radius is varied in such a way that plasma electron densities (∼1020−1026 per cm3) cover a wide range of experimental interest. Both relativistic and non-relativistic energies of 2p2(3P) and 1s2p(3P) states are reported. The relativistic MCDF results are obtained by modified GRASP2K code and the non-relativistic variational results are done by using explicitly correlated Hylleraas basis. The relativistic results are in good agreement with experimental data available in literature. The positions of intercombination lines in presence of dense plasma can be calculated from present results which are comparable with experimental measurements. The partial pressures experienced by the plasma-embedded ions are analyzed in the purview of available experimental observations. An empirical relation is reported to estimate partial pressure on ions in dense plasma environment.

Full set of relaxation constants for 174Yb level (6s6p) 3P1 in collisions with rare gases

For the first time, a complete set of decay parameters, due to collisions of 174Yb atoms with noble gas atoms and with ytterbium atoms, was experimentally found for the 174Yb (6s6p) 3P1 level. The method of stimulated photon echo with special angles between the polarization vectors of light pulses forming an echo at the 174Yb (6s2) 1S0—(6s6p) 3P1 transition (type ) is used. For each buffer gas of He, Ne, Ar, Kr, Xe, and Yb, the decay rate constants of population, orientation and alignment for the collision destruction of the 3P1 level of 174Yb atoms are determined. All the decay rates demonstrated their linear increase with a buffer gas pressure, and the corresponding relaxation constants are determined. Each of the indicated relaxation constants, as well as the difference between the alignment and orientation relaxation constants, increases with the increasing buffer gas mass.

Investigation on the DC Stark shifts of strontium autoionization states for isotope-selective resonance ionization

Three-step resonance excitation to autoionization states is a promising isotope-selective ionization technique for atomic strontium (Sr). We measured for the first time the DC Stark shifts of ten Rydberg levels (neff∼36−39,50−55) of 88Sr converging to the 4d 2D3/2 limit using the 5s21S0→ 5s5p 1P1∘→ 5p21D2→ (4d 2D3/2 Rydberg series) transition pathway. The polarizability α of each level was evaluated to be |α|∼10−30−10−28 [C2·m2·J−1] depending on the effective principal quantum number neff, which indicates that the external electric field E in the ionization region should be of the order of 0.1 V/cm or less to suppress its effect on the observed spectra. Our experimental data on the DC Stark shift and polarizability of the Rydberg levels are useful for future isotope-selective detection of the radioisotope 90Sr using three-step resonance excitation.

Modeling of the thermal migration mechanisms of atomic oxygen in Ar, Kr, and Xe crystals.

Accommodation and migration of the ground-state (2s22p4 3P) oxygen atom in the ideal Ar, Kr, and Xe rare gas crystals are investigated using the classical model. The model accounts for anisotropy of interaction between guest and host atoms, spin-orbit coupling, and lattice relaxation. Interstitial and substitutional accommodations are found to be the only thermodynamically stable sites for trapping atomic oxygen. Mixing of electronic states coupled to lattice distortions justifies that its long-range thermal migration follows the adiabatic ground-state potential energy surface. Search for the migration paths reveals a common direct mechanism for interstitial diffusion. Substitutional atoms are activated by the point lattice defects, whereas the direct guest-host exchange meets a higher activation barrier. These three low-energy migration mechanisms provide plausible interpretation for multiple migration activation thresholds observed in Kr and Xe free-standing crystals, confirmed by reasonable agreement between calculated and measured activation energies. An important effect of interaction anisotropy and a minor role of spin-orbit coupling are emphasized.