Atomic Spectroscopic Databases at NIST

We describe recent work at NIST to develop and maintain databases for spectra, transition probabilities, and energy levels of atoms that are astrophysically important. Our programs to critically compile these data as well as to develop a new database to compare plasma calculations for atoms that are not in local thermodynamic equilibrium are also summarized

EUV spectra of highly-charged ions W54+^{54+}-W63+^{63+} relevant to ITER diagnostics

We report the first measurements and detailed analysis of extreme ultraviolet (EUV) spectra (4 nm to 20 nm) of highly-charged tungsten ions W$^{54+}$ to W$^{63+}$ obtained with an electron beam ion trap (EBIT). Collisional-radiative modelling is used to identify strong electric-dipole and magnetic-dipole transitions in all ionization stages. These lines can be used for impurity transport studies and temperature diagnostics in fusion reactors, such as ITER. Identifications of prominent lines from several W ions were confirmed by measurement of isoelectronic EUV spectra of Hf, Ta, and Au. We also discuss the importance of charge exchange recombination for correct description of ionization balance in the EBIT plasma.Comment: 11 pages, 4 figure

Spectra of W39+^{39+}-W47+^{47+} in the 12 nm to 20 nm region observed with an EBIT light source

We observed spectra of highly ionized tungsten in the extreme ultraviolet with an electron beam ion trap (EBIT) and a grazing incidence spectrometer at the National Institute of Standards and Technology. Stages of ionization were distinguished by varying the energy of the electron beam between 2.1 keV and 4.3 keV and correlating the energies with spectral line emergence. The spectra were calibrated by reference lines of highly ionized iron produced in the EBIT. Identification of the observed lines was aided by collisional-radiative modeling of the EBIT plasma. Good quantitative agreement was obtained between the modeling results and the experimental observations. Our line identifications complement recent results for W$^{40+}$-W$^{45+}$ observed in a tokamak plasma by P\"{u}tterich {\it et al} (\jpb {\bf 38}, 3071, 2005). For most lines we agree with their assignment of ionization stage. Additionally, we present new identifications for some allowed and forbidden lines of W$^{39+}$, W$^{44+}$, W$^{46+}$, and W$^{47+}$. The uncertainties of our wavelengths range from 0.002 nm to 0.010 nm.Comment: 19 pages, 8 figure

Production of Sodium Bose--Einstein condensates in an optical dimple trap

We report on the realization of a sodium Bose--Einstein condensate (BEC) in a combined red-detuned optical dipole trap, formed by two beams crossing in a horizontal plane and a third, tightly focused dimple trap propagating vertically. We produce a BEC in three main steps: loading of the crossed dipole trap from laser-cooled atoms, an intermediate evaporative cooling stage which results in efficient loading of the auxiliary dimple trap, and a final evaporative cooling stage in the dimple trap. Our protocol is implemented in a compact setup and allows us to reach quantum degeneracy even with relatively modest initial atom numbers and available laser power

Modelling of spectral properties and population kinetics studies of inertial fusión and laboratory astrophysical plasmas

Fundamental research and modelling in plasma atomic physics continue to be essential for providing basic understanding of many different topics relevant to high-energy-density plasmas. The Atomic Physics Group at the Institute of Nuclear Fusion has accumulated experience over the years in developing a collection of computational models and tools for determining the atomic energy structure, ionization balance and radiative properties of, mainly, inertial fusion and laser-produced plasmas in a variety of conditions. In this work, we discuss some of the latest advances and results of our research, with emphasis on inertial fusion and laboratory-astrophysical applications

O 1s excitation and ionization processes in the CO2 molecule studied via detection of low-energy fluorescence emission

Oxygen 1s excitation and ionization processes in the CO2 molecule have been studied with dispersed and non-dispersed fluorescence spectroscopy as well as with the vacuum ultraviolet (VUV) photon?photoion coincidence technique. The intensity of the neutral O emission line at 845 nm shows particular sensitivity to core-to-Rydberg excitations and core?valence double excitations, while shape resonances are suppressed. In contrast, the partial fluorescence yield in the wavelength window 300?650 nm and the excitation functions of selected O+ and C+ emission lines in the wavelength range 400?500 nm display all of the absorption features. The relative intensity of ionic emission in the visible range increases towards higher photon energies, which is attributed to O 1s shake-off photoionization. VUV photon?photoion coincidence spectra reveal major contributions from the C+ and O+ ions and a minor contribution from C2+. No conclusive changes in the intensity ratios among the different ions are observed above the O 1s threshold. The line shape of the VUV?O+ coincidence peak in the mass spectrum carries some information on the initial core excitatio