Proposal for laser-cooling of rare-earth ions

The efficiency of laser-cooling relies on the existence of an almost closed optical-transition cycle in the energy spectrum of the considered species. In this respect rare-earth elements exhibit many transitions which are likely to induce noticeable leaks from the cooling cycle. In this work, to determine whether laser-cooling of singly-ionized erbium Er$^+$ is feasible, we have performed accurate electronic-structure calculations of energies and spontaneous-emission Einstein coefficients of Er$^+$, using a combination of \textit{ab initio} and least-square-fitting techniques. We identify five weak closed transitions suitable for laser-cooling, the broadest of which is in the kilohertz range. For the strongest transitions, by simulating the cascade dynamics of spontaneous emission, we show that repumping is necessary, and we discuss possible repumping schemes. We expect our detailed study on Er$^+$ to give a good insight into laser-cooling of neighboring ions like Dy$^+$.Comment: 5 pages, 2 figure

Energy levels and transition probabilities in doubly-ionized erbium (Er III)

The spectrum of Er III reported by Becher (1966) was reanalysed with the support of new predictions of energies and transition probabilities. The number of energy levels was increased from 45 to 115, including two levels of 4f117s and the levels 3F3, 3F2 and 1G4 of the ground configuration 4f12. All 470 classified lines are reported with transition probabilities for most of them. Several of these lines had not yet been attributed to Er III in the spectrum of the star HR465.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49231/2/physscr_56_5_008.pd

Étude des configurations paires 4 f4 6 s et 4 f4 5 d de Nd II

The classification of Nd II spectrum has led to the discovery of 47 new low levels which belong to the 4 f4 6 s and 4 f 4 5 d configurations. The theoretical calculation of the energy eigen values and the Landé g-factors of the two configurations taken together has allowed the interpretation of the 78 experimental levels with a r. m. s. error of 57 K. Eigen vectors are given in the LS scheme. The values of the radial parameters have been fitted by the least-squares method.La classification du spectre de Nd II a entraîné la découverte de 47 nouveaux niveaux pairs profonds appartenant à 4 f4 6 s et 4 f4 5 d. Les calculs théoriques des énergies et des facteurs de Landé des niveaux de l'ensemble de ces configurations ont permis d'interpréter les 78 niveaux expérimentaux avec un écart quadratique moyen de 57 K. Les vecteurs propres sont donnés dans le couplage LS. Nous avons ajusté les paramètres radiaux par la méthode des moindres carrés

Theoretical interpretation and new energy levels in Er II

International audienceIn this work, we extend the classification of the spectrum of singly ionized erbium (Er II) both theoretically and experimentally. First, the known energy levels are interpreted parametrically using the Cowan code on two sets of configurations with interaction. Then the predictions for unknown levels are used to extend the classification of hollow cathode FT spectra of erbium recorded at the US National Solar Observatory on Kitt Peak. All 130 known levels of even parity are described with a root mean square deviation of 61 cm-1 and the summed contributions of 4f126s, 4f125d, 4f116s6p and 4f115d6p in their eigenvectors are presented. A similar agreement is obtained for 230 energy levels of odd parity. The detailed configuration percentages show that the levels of 4f126p are strongly mixed with 4f116s5d and 4f115d2. The transition probabilities obtained by means of the Cowan code are in a good qualitative agreement with the observed intensities of the classified lines and they are reported with the chains of transitions of 32 new energy levels and revised J-values for six additional levels. The energy level values and uncertainties are derived by least squares from the complete transition array of Er II with natural isotopic blending, whereas earlier compiled levels had been derived from the 168Er isotope

FitAik: a package to calculate least-squares fitted atomic transitions probabilities. Application to the Er + lanthanide ion

International audienceWe present a new method implemented in our new package FitAik, to perform least-squares fitting of calculated and experimental atomic transition probabilities, by using the mono-electronic transition integrals n |r|n (with r the electronic radial coordinate) as adjustable quantities. FitAik is interfaced to the Cowan suite of codes, for which it automatically writes input files and reads output files. We illustrate our procedure with the example of Er + ion, for which the agreement between calculated and experimental Einstein coefficients is found to be very good. The source code of FitAik can be found on GitLab, and the calculated Einstein coefficients are stored in our new database CaDDiACs. They are also used to calculate the dynamic dipole polarizability of Er +

Mesure et interprétation de spectres de lanthanides faiblement ionisés dans l'ultraviolet (cas du néodyme et du thulium)

Le spectre d émission d éléments de lanthanides ionisés est observé et mesuré sur des spectrographes en incidence normale dans l ultraviolet(70-275nm). Les récepteurs sont des plaques argentiques ou des écrans photostimulables. Pour le néodyme, les raies de Nd III, IV et V sont discriminées expérimentalement en faisant varier les conditions d excitation de l étincelle. L étude des configurations électroniques selon les méthodes de Racah-Slater au moyen des programmes de Cowan conduit à trouver les niveaux des ions libres Nd3+ et Nd4+. Les 41 niveaux de 4f3 (Nd IV) et les 12 niveaux de 4f2 (Nd V) sont interprétés paramétriquement en tenant compte des interactions de configuration au 3 ordre de perturbation électrostatique et au 2 ordre pour les interactions du spin (écart quadratique moyen = 1/13000 du domaine d énergie interprété). Pour Nd IV, on rapporte 1426 raies avec leur classification, et les probabilités de transition gA calculées. Pour la première fois, le rôle des configurations de cœur excité sur les transitions de résonance 4f N+1-4fN5d, via l interaction 5p64f N-15d-5p54f n5d, est mis en évidence. Les méthodes sont appliquée au spectre, totalement inconnu auparavant de Tm IV, pour lequel 760 raies sont classées et les probabilités de transitions calculées. Dans le cas de Nd V, la comparaison des intensités calculées à l ETL et observées conduit à une température effective Teff=3,6(3)eV dans l étincelle.The emission spectrum of lanthanide elements is observed an measured on normal incidence spectrographs (70-275nm). Argentic plates or phosphor image plates are used as receptors. In the case of neodymium, spark excitation conditions are varied to discriminate Nd III, IV and V spectral lines. The electronic configurations of the Cowan codes. The 41 levels of 4f3 (Nd IV) and 12 levels of 4f2(Nd V) are interpreted parametrically by taking into account the configuration interaction effects at the 3rd order of perturbation and all spin dependent effects at the 2nd order , with a root mean square deviation of 1/13000 of the interpreted energy range. In Nd IV, 1426 lines are reported with the combining levels, the calculated transition probabilities gA. For the first time the importance of the interaction 5p64f N-15d-5p54fN5d on the resonance transitions 4f N+1-4fN5d is evidenced. The same methods are applied to the formely unknown spectrum of Tm IV, that comprises now 760 classified lines (with calculated transition probabilities), involving 209 energy levels. In the case of Nd V, the comparison of ETL computed versus measured intensities leads to Teff=3,6(3)eV in the spark.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

FitAik: a package to calculate least-square fitted atomic transitions probabilities. Application to the Er+ lanthanide ion

International audienceWe present a new method implemented in our new package \textit{FitAik}, to perform least-square fitting of calculated and experimental atomic transition probabilities, by using the mono-electronic transition integrals $\langle n\ell |r| n'\ell' \rangle$ as adjustable quantities. \textit{FitAik} is interfaced to the Cowan suite of codes, for which it automatically writes input files and reads output files. We illustrate our procedure with the example of Er$^{+}$ ion, for which the agreement between calculated and Einstein coefficients is found very good. The source code of \emph{FitAik} can be found on GitLab, and the calculated Einstein coefficients are stored in our new database CaDDiACs

Anisotropic optical trapping as a manifestation of the complex electronic structure of ultracold lanthanide atoms: The example of holmium

International audienc