Radium single-ion optical clock

We explore the potential of the electric quadrupole transitions 7s\,^2S_{1/2} - 6d\,^2D_{3/2}, 6d\,^2D_{5/2} in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated. Several competitive $^A$Ra$^+$ candidates with $A=$ 223 - 229 are identified. In particular, we show that the transition 7s\,^2S_{1/2}\,(F=2,m_F=0) - 6d\,^2D_{3/2}\,(F=0,m_F=0) at 828 nm in $^{223}$Ra$^+$, with no linear Zeeman and electric quadrupole shifts, stands out as a relatively simple case, which could be exploited as a compact, robust, and low-cost atomic clock operating at a fractional frequency uncertainty of $10^{-17}$. With more experimental effort, the $^{223,225,226}$Ra$^+$ clocks could be pushed to a projected performance reaching the $10^{-18}$ level.Comment: 20 pages, 1 figur

Hadronic Vacuum Polarization Contribution to the Muonium Hyperfine Splitting

We discuss hadronic effects in the muonium hyperfine structure and derive an expression for the hadronic contribution to the hfs interval in form of the one-dimensional integral of the cross section of e+e- annihilation into hadrons. Higher-order hadronic contributions are also considered

Aspects of Cooling at the TRIμ\muP Facility

The Tri$\mu$P facility at KVI is dedicated to provide short lived radioactive isotopes at low kinetic energies to users. It comprised different cooling schemes for a variety of energy ranges, from GeV down to the neV scale. The isotopes are produced using beam of the AGOR cyclotron at KVI. They are separated from the primary beam by a magnetic separator. A crucial part of such a facility is the ability to stop and extract isotopes into a low energy beamline which guides them to the experiment. In particular we are investigating stopping in matter and buffer gases. After the extraction the isotopes can be stored in neutral atoms or ion traps for experiments. Our research includes precision studies of nuclear $\beta$-decay through $\beta$-$\nu$ momentum correlations as well as searches for permanent electric dipole moments in heavy atomic systems like radium. Such experiments offer a large potential for discovering new physics.Comment: COOL05 Workshop, Galena, Il, USA, 18-23. Sept. 2005, 5 pages, 3 figure

Investigations of Ra+^+ properties to test possibilities of new optical frequency standards

The present work tests the suitability of the narrow transitions $7s \ ^2S_{1/2} \to 6d ^2D_{3/2}$and$7s ^2S_{1/2} \to 6d ^2D_{5/2}$in Ra$^+$for optical frequency standard studies. Our calculations of the lifetimes of the metastable$6d$states using the relativistic coupled-cluster theory suggest that they are sufficiently long for Ra$^+$ to be considered as a potential candidate for an atomic clock. This is further corroborated by our studies of the hyperfine interactions, dipole and quadrupole polarizabilities and quadrupole moments of the appropriate states of this system.Comment: Latex files, 5 pages, 1 figur

On-line Excited-State Laser Spectroscopy of Trapped Short-Lived Ra+^+ Ions

As an important step towards an atomic parity violation experiment in one single trapped Ra$^+$ ion, laser spectroscopy experiments were performed with on-line produced short-lived $^{212,213,214}$Ra$^+$ ions. The isotope shift of the 6\,^2D$_{3/2}$\,-\,7\,^2P$_{1/2}$ and 6\,^2D$_{3/2}$\,-\,7\,^2P$_{3/2}$ transitions and the hyperfine structure constant of the 7\,^2S$_{1/2}$ and 6\,^2D$_{3/2}$ states in $^{213}$Ra$^+$ were measured. These values provide a benchmark for the required atomic theory. A lower limit of $232(4)$ ms for the lifetime of the metastable 6\,^2D$_{5/2}$ state was measured by optical shelving.Comment: 4.2 pages, 6 figures, 2 tables

Thermal Analysis of EPOS components

We present a simulation study of the thermal behaviour of essential parts of the electron-positron converter of the positron source EPOS at the Research Center Dresden-Rossendorf. The positron moderator foil and the upper tube element of the electrostatic extraction einzellens are directly exposed to the primary electron beam (40 MeV, 40 kW). Thus, it was necessary to prove by sophisticated simulations that the construction can stand the evolving temperatures. It was found that thin moderator foils (< 20...40 µm) will not show a too strong heating. Moreover, the temperature can be varied in a wide range by choosing an appropriate thickness. Thus, the radiation-induced lattice defects can at least partly be annealed during operation. The wall of the extraction lens which is made from a stainless steel tube must be distinctly thinned to avoid damage temperatures. The simulations were performed time dependent. We found that the critical parts reach their final temperature after less than a minute

Melhoramento molecular como ferramenta para aumentar a qualidade das forrageiras tropicais Brachiaria brizantha e Panicum maximum.

As pastagens constituem a principal fonte de alimentação dos bovinos no Brasil. O desempenho desses animais em pastagens depende do potencial genético do animal, da disponibilidade de forragem na pastagem, da qualidade desta forragem e do consumo da mesma por parte do animal (CÓSER et al., 2008). Cabe ressaltar que em criações que visam produção de carne, o acréscimo no desempenho dos bovinos resulta em menor permanência do animal no sistema, reduzindo a produção de metano (CH4) durante o seu ciclo de vida, contribuindo para mitigar a emissão de gases de efeito estufa (GEE). Dentre as principais espécies utilizadas nas pastagens brasileiras estão Brachiaria brizantha e Panicum maximum, gramíneas tropicais (C4), de origem africana, amplamente adaptadas às condições edafo-climáticas do País. Elas apresentam elevada taxa de crescimento e produção de matéria seca, em virtude da maior eficiência na fixação de carbono (C4) em relação às gramíneas temperadas (C3), porém a sua qualidade (proteína e digestibilidade) é, em geral, inferior a das gramíneas temperadas (C3), cuja degradação ruminal é mais rápida devido à parede celular menos espessa, ou seja, com menor teor de compostos indigeríveis, como a lignina (CABRAL et al., 2004). Tendo em vista a complexidade genética de B. brizantha e P. maximum (poliplóides e apomíticas) novas técnicas genômicas e da biotecnologia moderna (transgenia) apresentam-se como abordagens promissoras para obtenção de novas cultivares com melhor qualidade. Para viabilizar esta abordagem sem o pagamento de taxas de licenciamento e ?royalties? há necessidade de se buscar genes e promotores que possam ser utilizados em construções gênicas para obtenção dessas gramíneas forrageiras tropicais geneticamente melhoradasPoster 058