Laser spectroscopy of trapped Ra+ ions : towards a single-ion optical clock

A single trapped and laser-cooled radium ion, Ra+, is a promising candidate for high precision experiments, such as on atomic parity violation (APV) and atomic clocks. APV experiments provide a stringent test of the Standard Model of particles physics with high sensitivity for physics beyond. Ultra-narrow transitions in Ra+ can be employed for optical frequency standards, or “clocks”. As an important step towards such experiments excited-state laser spectroscopy was performed on short-lived trapped 209-214Ra+ ions produced from the AGOR cyclotron at KVI. Hyperfine structure constants of Ra+ atomic states and isotope shifts of relevant transitions were studied, providing benchmarks for the required atomic theory at percent level accuracy. The measurement of a lower limit of the lifetime of the meta-stable 6d2D5/2 state provides an important confirmation of the fundamental availability of long coherence times in the trapped Ra+ system, required for high-quality clocks. The potential of the electric quadrupole transitions 7s2S1/2 -6d2D3/2 , 6d2D5/2 in Ra+ isotopes as single-ion optical frequency standards was explored. The frequency shifts of the clock transitions due to external fields and corresponding uncertainties were calculated. Several competitive candidates have been identified. In particular, the transition 7s2S1/2 (F=2,mF=0)-6d2D3/2(F=0,mF=0) in 223Ra+ at 828nm wavelength stands out because of the absence of linear Zeeman and electric quadrupole shifts. It 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 223,225,226Ra+ clocks could be pushed to a projected performance reaching even the 10-18 level.

Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

We present and experimentally validate a model describing the sensitivity of the tilt angle, expansion and propulsion velocity of a tin micro-droplet irradiated by a 1 {\mu}m Nd:YAG laser pulse to its relative alignment. This sensitivity is particularly relevant in industrial plasma sources of extreme ultraviolet light for nanolithographic applications. Our model has but a single parameter: the dimensionless ratio of the laser spot size to the effective size of the droplet, which is related to the position of the plasma critical density surface. Our model enables the development of straightforward scaling arguments in turn enabling precise control the alignment sensitivity.Comment: 7 pages, 5 figure

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

Grizzly Den set for January 13, 1981

Desenvolvemos, no programa de extensão interinstitucional (Unifesp, USP e IFSP) Banca da Ciência a divulgação científica, em vários ambientes, com uma metodologia que privilegia o lúdico, o dialogismo e as interações sociais. O objetivo do programa Banca da Ciência é apresentar conceitos científicos de uma forma lúdica e interativa para estudantes da escola básica e para outros interessados. Para isso contamos com a Banca da Ciência, uma estrutura em forma de banca de jornal adaptada para receber equipamentos científicos e didáticos e com espaço para sua manipulação por grupos de estudantes funcionando como espaço expositivo, além laboratório de investigação e divulgação de ciências. A partir das diferentes demandas, espaços e formatos com os quais trabalhamos, são caracterizadas e delimitadas ações e pesquisas em diferentes projetos que se caracterizam por diferentes públicos, espaços e modalidades de ações. Esses projetos são nomeados por siglas representando personagens de ficção e/ou fantasia. Joaninha, Ellie e Susan Calvin são três projetos desenvolvidos pela Escola de Filosofia, Letras e Ciências Humanas da Universidade Federal de São Paulo (EFLCH-Unifesp) desde 2018 em colaboração com o subprojeto Pedagogia do Pibid Unifesp. Dito isso, objetivamos, nesse trabalho, descrever a estrutura e as ações do programa Banca da Ciência articulada com a formação dos graduandos do curso de Pedagogia, no campus Guarulhos da Unifesp, contribuindo assim para uma experiência na interface divulgação cientifica–ensino de ciências.We developed, in the interinstitutional extension program (Unifesp, USP and IFSP) Science Stand, the science outreach in various environments, with a methodology that privileges the playful, dialogism and social interactions. The goal of the Science Stand program is to present scientific concepts in a playful and interactive way for elementary school students and other stakeholders. For this, we have the Newsstand, a structure in the form of a newsstand adapted to receive scientific and didactic equipment and with space for its manipulation by groups of students working as an exhibition space, as well as a research and science outreach laboratory. From the different demands, spaces and formats with which we work, actions and researches are characterized and delimited in different projects, which are characterized by public, spaces and modalities of actions and, which are given names with acronyms representing fictional and/or fantasy characters. Joaninha, Ellie and Susan Calvin are three projects developed by the School of Philosophy, Letters and Human Sciences of the Federal University of São Paulo (EFLCH-Unifesp), since 2018 in collaboration with the Pibid Unifesp Pedagogy subproject. That said, we aim, in this paper, to describe the structure and actions of the Science Stand program articulated with the training of Pedagogy undergraduates at the Unifesp Guarulhos campus, thus contributing to an experience in the interface science outreach - science education

Short-wavelength out-of-band EUV emission from Sn laser-produced plasma

We present the results of spectroscopic measurements in the extreme ultraviolet (EUV) regime (7-17 nm) of molten tin microdroplets illuminated by a high-intensity 3-J, 60-ns Nd:YAG laser pulse. The strong 13.5 nm emission from this laser-produced plasma is of relevance for next-generation nanolithography machines. Here, we focus on the shorter wavelength features between 7 and 12 nm which have so far remained poorly investigated despite their diagnostic relevance. Using flexible atomic code calculations and local thermodynamic equilibrium arguments, we show that the line features in this region of the spectrum can be explained by transitions from high-lying configurations within the Sn$^{8+}$-Sn$^{15+}$ ions. The dominant transitions for all ions but Sn$^{8+}$ are found to be electric-dipole transitions towards the $n$=4 ground state from the core-excited configuration in which a 4$p$ electron is promoted to the 5$s$ sub-shell. Our results resolve some long-standing spectroscopic issues and provide reliable charge state identification for Sn laser-produced plasma, which could be employed as a useful tool for diagnostic purposes.Comment: 11 pages, 4 figure

Microdroplet-tin plasma sources of EUV radiation driven by solid-state-lasers (Topical Review)

Plasma produced from molten-tin microdroplets generates extreme ultraviolet light for state-of-the-art nanolithography. Currently, CO2 lasers are used to drive the plasma. In the future, solid-state mid-infrared lasers may instead be used to efficiently pump the plasma. Such laser systems have promise to be more compact, better scalable, and have higher wall-plug efficiency. In this Topical Review, we present recent findings made at the Advanced Research Center for Nanolithography (ARCNL) on using 1 and 2 μm wavelength solid-state lasers for tin target preparation and for driving hot and dense plasma. The ARCNL research ranges from advanced laser development, studies of fluid dynamic response of droplets to impact, radiation-hydrodynamics calculations of, e.g. ion 'debris', (EUV) spectroscopic studies of tin laser-produced-plasma as well as high-conversion efficiency operation of 2 μm wavelength driven plasma

Antonio Negri. Marx além de Marx: ciência da crise e da subversão

Resenha do livro de Negri, Antonio. Marx além de Marx: ciência da crise e da subversão. Caderno de trabalho sobre os Grundrisse