Magneto-optical trapping of bosonic and fermionic neon isotopes and their mixtures: isotope shift of the ^3P_2 to ^3D_3 transition and hyperfine constants of the ^3D_3 state of Ne-21

We have magneto-optically trapped all three stable neon isotopes, including the rare Ne-21, and all two-isotope combinations. The atoms are prepared in the metastable ^3P_2 state and manipulated via laser interaction on the ^3P_2 to ^3D_3} transition at 640.2nm. These cold (T = 1mK) and environmentally decoupled atom samples present ideal objects for precision measurements and the investigation of interactions between cold and ultracold metastable atoms. In this work, we present accurate measurements of the isotope shift of the ^3P_2 to ^3D_3 transition and the hyperfine interaction constants of the ^3D_3 state of Ne-21. The determined isotope shifts are (1625.9\pm0.15)MHz for Ne-20 to Ne-22, (855.7\pm1.0)MHz for Ne-20 to Ne-21, and (770.3\pm1.0)MHz for Ne-21 to Ne-22. The obtained magnetic dipole and electric quadrupole hyperfine interaction constants are A(^3D_3)= (-142.4\pm0.2)MHz and B(^3D_3)=(-107.7\pm1.1)MHz, respectively. All measurements give a reduction of uncertainty by about one order of magnitude over previous measurements

On the alpha activity of natural tungsten isotopes

The indication for the alpha decay of 180-W with a half-life T1/2=1.1+0.8-0.4(stat)+-0.3(syst)x10^18 yr has been observed for the first time with the help of the super-low background 116-CdWO_4 crystal scintillators. In conservative approach the lower limit on half-life of 180-W has been established as T1/2>0.7x10^18 yr at 90% C.L. Besides, new T1/2 bounds were set for alpha decay of 182-W, 183-W, 184-W and 186-W at the level of 10^20 yr.Comment: 16 pages, 8 figures, accepted in Phys. Rev.

Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra

[Abridged] We previously presented evidence for a varying fine-structure constant, alpha, in two independent samples of Keck/HIRES QSO spectra. Here we present a detailed many-multiplet analysis of a third Keck/HIRES sample containing 78 absorption systems. We also re-analyse the previous samples, providing a total of 128 absorption systems over the redshift range 0.2<z_abs<3.7. All three samples separately yield consistent, significant values of da/a. The analyses of low- and high-z systems rely on different ions/transitions with very different dependencies on alpha, yet they also give consistent results. We identify additional random errors in 22 high-z systems characterized by transitions with a large dynamic range in apparent optical depth. Increasing the statistical errors on da/a for these systems gives our fiducial result, a weighted mean da/a=(-0.543+/-0.116)x10^-5, representing 4.7-sigma evidence for a smaller weighted mean alpha in the absorption clouds. Assuming that da/a=0 at z_abs=0, the data marginally prefer a linear increase in alpha with time: dota/a=(6.40+/-1.35)x10^-16 yr^-1. The two-point correlation function for alpha is consistent with zero over 0.2-13 Gpc comoving scales and the angular distribution of da/a shows no significant dipolar anisotropy. We therefore have no evidence for spatial variations in da/a. We extend our previous searches for possible systematic errors, identifying atmospheric dispersion and isotopic structure effects as potentially the most significant. However, overall, known systematic errors do not explain the results. Future many-multiplet analyses of QSO spectra from different telescopes and spectrographs will provide a now crucial check on our Keck/HIRES results.Comment: 31 pages, 25 figures (29 EPS files), 8 tables. Accepted by MNRAS. Colour versions of Figs. 6, 8 & 10 and text version of Table 3 available at http://www.ast.cam.ac.uk/~mim/pub.htm

Strontium isotope measurements in Greenland ice from the last glacial maximum to the early Holocene

Strontium isotopic composition and concentration have been measured by thermal ionisation mass spectrometry on a suite of samples from the GRIP ice core drilled at Summit, Greenland. The sample ages range from ~24 to ~7.3 ky BP extending from the last glacial maximum into the early Holocene. Less than 10 g of sample was used for each analysis. No attempt was made to separate soluble/insoluble species in the samples. Sr concentrations are between ~950 and ~1,550 pg.g$^{-1}$ over the period ~24 ky to ~14 ky BP but fall dramatically to generally less than 150 pg.g$^{-1}$ between ~14 to ~7.3 ky BP. The $^{87}$Sr/$^{86}$Sr ratio shows a general rising trend from ~0.712 to ~0.715 over the entire period however there are a number of significant deviations from this trend which are most likely due to changing source regions for aerosol dust input to Greenland. Sr isotopic composition shows a strong correlation with $\delta^{80}$O suggesting that climate plays a strong role in determining regions for dust release

Isotopic and elemental relics of the 1815 AD Tambora eruption in ice from Law Dome, Antarctica

Lead isotopes and Pb, Ba and Bi concentrations have been recently measured at sub-annual resolution in an ice core section from Law Dome, Antarctica, corresponding to the period 1814-1819 AD and containing a SO$^{2-}_4$signal attributed to the 1815 AD eruption of Tambora volcano in Indonesia. While increasing concentrations of Pb and Bi coincide with the 1817-1818 AD volcanic SO$_4^{2-}$ peak, Pb isotope data do not confirm Tambora as the source. Barium concentrations were elevated from 1816.5 to 1818.5 AD, indicating increased atmospheric dust levels. These findings contribute to the growing body of data indicating that effusive, rather than explosive, volcanism is the most important volcanic emission process determining the flux of volcanogenic heavy metals to the polar ice sheets

One hundred fifty-year record of lead isotopes in Antarctic snow from Coats Land

A record of the concentrations of Pb and Ba and the isotopic composition of Pb has been established for a remote, low accumulation site in the Atlantic sector of Antarctica (Coats Land) by means of thermal ionization mass spectrometry. The snow samples cover the period similar to 1840 to 1990. They were taken from the walls of a pit to a depth of 7.8 nu and as a core to 16 m; ultraclean procedures were used. Detailed laboratory subsampling provided both long-term (secular scale) and short-term (intra-annual) Pb, Ba, and Pb isotope variations. The results show that there have been significant variations in Ph concentrations (range, 0.1 to 9.3 pg/g) and isotopic composition (range, 1.096 to 1,208 for Pb-206/Pb-207 ratio) since the 1840s. The data show evidence of pollution for this metal in Antarctica as early as the 1880s. Several Pb maxima were observed: the first at the beginning of the 20th century and the last in the 1970s to 1980s, with a clear decrease during recent years. Although the last maximum is clearly linked to the rise and fall in the use of leaded gasoline in the Southern Hemisphere, especially in South America, the reason for the first remains uncertain. The pattern of changing isotopic composition of Ph reveals the changing origin and character of the anthropogenic inputs to Antarctica. An interesting feature in this pattern is the relatively large contribution of unradiogenic Pb in the similar to1890s, possibly originating from Australia. Another interesting feature is the pronounced intra-annual variation in the isotopic composition of Pb, which illustrates the complexity of the changing inputs of Pb to Antarctica

Isotopic Composition of the Elements 2001

The Commission on Atomic Weights and Isotopic Abundances of the Intenational Union of Pure and Applied Chemistry completed its last review of the isotopic compositions of the elements as determined by isotope ratio mass spectrometry in 2001. That review involved a critical evaluation of the published literature, element by element, and from the basis of the table of isotopic compositions of the elements (TICE) presented here. For each element, TICE includes evaluated data from the ¿best measurement¿ of the isotope abundances in a single sample, along with a set of representative isotope abundances and uncertainties that accommodate known variations in normal terrestrial materials. The representative isotope abundances and uncertainties generally are consistent with the standard atomic weight of the element Ar(E) and its uncertainty U[Ar(E)] recommended by CAWIA in 2001.JRC.D.4-Isotope measurement