Single ion spectroscopy in preparation of an atomic parity violation measurement in Ra+

Precisiemetingen van atomaire pariteitsviolatie (APV) vormen een stringente test van het Standaardmodel voor deeltjesfysica. De bepaling van de Weinberghoek (sin^2θ_W), bij lage energieën in het bijzonder, maakt het mogelijk om naar fysica buiten het Standaardmodel te zoeken. De precisie waarmee deze parameter kan worden verkregen hangt af van de nauwkeurigheid van de kennis van de atomaire golffuncties, die voor systemen met één valentie-elektron zoals Ba+ en Ra+-ionen nauwkeurig kunnen worden berekend. APV-effecten zijn het grootst in zware atomen, waardoor Ra^+ een zeer geschikt systeem vormt voor een dergelijke meting. In dit werk onderwerpen we verschillende in een val opgesloten Ra+-isotopen aan laserspectroscopie. De frequentie voor de 7s^2S_(1/2)-6d^2D_(3/2) overgang in de isotopen (212-214)Ra+ is daarmee tot op 19 MHz nauwkeurigheid gemeten. Een competetieve meting van APV met Ra+ vereist één enkel gelokaliseerd ion. Vanwege de radioactiviteit van alle Ra+ isotopen wordt het enkele-ionenexperiment aan het Van Swinderen Instituut ontwikkeld met het chemisch homologe Ba+ als voorloper voor Ra+. Hieraan zijn laserspectroscopie en metingen van levensduren van Ba+ verricht. De frequenties van de 6s^2S_(1/2)-6p^2P_(1/2), 5d^2D_(3/2)-6p^2P_(1/2) en 6s^2S_(1/2)-5d^2D_(3/2) overgangen zijn bepaald tot op 3 MHz nauwkeurig en vormen daarmee de tot op heden meest precieze metingen. De levensduur van de 5D_(5/2) toestand werd vastgesteld opτ_(5D_(5/2))=26.4(1.7)s, wat in goede overeenstemming is met theoretische voorspellingen en binnen twee standaardafwijkingen valt van eerder gedane metingen. De gemeten waardes kunnen worden gebruikt om de theoretische berekeningen aan Ba+-ionen te verbeteren. De resultaten die behaald zijn met Ba+ maken de weg vrij voor een APV-experiment met Ra+

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

A single-frequency, diode-pumped Nd:YLF laser at 657 nm: a frequency and intensity noise comparison with an extended cavity diode laser

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORWe report on a continuous wave, diode-pumped, intracavity frequency-doubled Nd:YLF (yttrium lithium fluoride) single-frequency ring laser designed for high-resolution spectroscopy of the calcium intercombination transition at 657 nm. We measured its frequency modulation (FM) and amplitude modulation (AM) noise and compared it with an extended cavity diode laser (ECDL). The Nd: YLF laser has much lower FM noise, extending to 50 kHz in comparison with 5 MHz for the ECDL, and slightly higher AM noise, transferred from the pump diode laser. This characterization is important for the design of servo-systems for frequency or intensity stabilization, and also for quantum optics experiments. A Nd: YLF laser at 657 nm can become an attractive high-power 'local oscillator' for a calcium optical clock, with a fundamental 'telecom wavelength' that can be directly used for remote transfer in optical fibers.We report on a continuous wave, diode-pumped, intracavity frequency-doubled Nd:YLF (yttrium lithium fluoride) single-frequency ring laser designed for high-resolution spectroscopy of the calcium intercombination transition at 657 nm. We measured its frequency modulation (FM) and amplitude modulation (AM) noise and compared it with an extended cavity diode laser (ECDL). The Nd: YLF laser has much lower FM noise, extending to 50 kHz in comparison with 5 MHz for the ECDL, and slightly higher AM noise, transferred from the pump diode laser. This characterization is important for the design of servo-systems for frequency or intensity stabilization, and also for quantum optics experiments. A Nd: YLF laser at 657 nm can become an attractive high-power 'local oscillator' for a calcium optical clock, with a fundamental 'telecom wavelength' that can be directly used for remote transfer in optical fibers.23214FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP [2006/53713-0]CEPOF [2005/51689-2]2006/53713-0; 2005/51689-2Sem informaçãoSem informaçãoThis work was supported by FAPESP (grant No. 2006/53713-0), CEPOF (grant No. 2005/51689-2), Fotonicom, CNPq and CAPES/COFECUB. We thank Richard Fox from NIST/Boulder for providing the AR-coated diode lasers

Ba+ Isotope shift studies in preparation of atomic parity violation measurement

The Ba+ ion, has a structure of spectral lines similar to heavy single valence electron alkali atoms. It is precisely studied by laser spectroscopy in presence of several light fields in order to prepare for a measurement of atomic parity violation (APV). Measurements in heavy alkali earth ions (e.g. Ba+ and Ra+) permit the precise determination of the weak mixing (Weinberg) angle sin2θW with improvement over the previous best measurement in neutral Cs by a factor of 5 in a week of actual measurement time. The transition frequencies for the 6s2S1/2 - 6p2P1/2, 6p2P1/2 - 5d2D3/2 and 6s2S1/2 - 5d2D3/2 transitions in 138Ba+ have been measured to 10−10 relative accuracy employing a line shape model for single ions in a radio frequency Paul trap [1]. These measurements have been extended to 134,136Ba+. Together with a determination of the lifetime of the excited 5d2D5/2 state these measurements provide for a stringent test of calculations, the accuracy of which is pivotal for a determination of sin2θW. The observed lifetime is 25.8(5)s. Being about 5s shorter than previous measurements and calculations agreeing with them, it provides for a puzzle. [1] E. A. Dijck et al., Phy. Rev. A 91, 060501(R)(2015

Ba+ Isotope shift studies in preparation of atomic parity violation measurement

The Ba+ ion, has a structure of spectral lines similar to heavy single valence electron alkali atoms. It is precisely studied by laser spectroscopy in presence of several light fields in order to prepare for a measurement of atomic parity violation (APV). Measurements in heavy alkali earth ions (e.g. Ba+ and Ra+) permit the precise determination of the weak mixing (Weinberg) angle sin2θW with improvement over the previous best measurement in neutral Cs by a factor of 5 in a week of actual measurement time. The transition frequencies for the 6s2S1/2 - 6p2P1/2, 6p2P1/2 - 5d2D3/2 and 6s2S1/2 - 5d2D3/2 transitions in 138Ba+ have been measured to 10−10 relative accuracy employing a line shape model for single ions in a radio frequency Paul trap [1]. These measurements have been extended to 134,136Ba+. Together with a determination of the lifetime of the excited 5d2D5/2 state these measurements provide for a stringent test of calculations, the accuracy of which is pivotal for a determination of sin2θW. The observed lifetime is 25.8(5)s. Being about 5s shorter than previous measurements and calculations agreeing with them, it provides for a puzzle. [1] E. A. Dijck et al., Phy. Rev. A 91, 060501(R)(2015