Characterizing the local vectorial electric field near an atom chip using Rydberg state spectroscopy

We use the sensitive response to electric fields of Rydberg atoms to characterize all three vector components of the local electric field close to an atom-chip surface. We measured Stark-Zeeman maps of $S$ and $D$ Rydberg states using an elongated cloud of ultracold Rubidium atoms ($T\sim2.5$ $\mu$K) trapped magnetically $100$ $\mu$m from the chip surface. The spectroscopy of $S$ states yields a calibration for the generated local electric field at the position of the atoms. The values for different components of the field are extracted from the more complex response of $D$ states to the combined electric and magnetic fields. From the analysis we find residual fields in the two uncompensated directions of $0.0\pm0.2$ V/cm and $1.98\pm0.09$ V/cm respectively. This method also allows us to extract a value for the relevant field gradient along the long axis of the cloud. The manipulation of electric fields and the magnetic trapping are both done using on-chip wires, making this setup a promising candidate to observe Rydberg-mediated interactions on a chip.Comment: 8 pages, 5 figure

Rydberg dressing of a one-dimensional Bose-Einstein condensate

We study the influence of Rydberg-dressed interactions in a one-dimensional (1D) Bose-Einstein condensate (BEC). We show that a 1D geometry offers several advantages over a three-dimensional geometry for observing BEC Rydberg dressing. The effects of dressing are studied by investigating collective BEC dynamics after a rapid switch-off of the Rydberg dressing interaction. The results can be interpreted as an effective modification of the s-wave scattering length. We include this modification in an analytical model for the 1D BEC and compare it to numerical calculations of Rydberg dressing under realistic experimental conditions.</p

Two-Electron Excitation of an Interacting Cold Rydberg Gas

We report the creation of an interacting cold Rydberg gas of strontium atoms. We show that the excitation spectrum of the inner valence electron is sensitive to the interactions in the Rydberg gas, even though they are mediated by the outer Rydberg electron. By studying the evolution of this spectrum we observe density-dependent population transfer to a state of higher angular momentum l. We determine the fraction of Rydberg atoms transferred, and identify the dominant transfer mechanism to be l-changing electron-Rydberg collisions associated with the formation of a cold plasma

Spectroscopy of a cold strontium Rydberg gas

We present a study of a cold strontium Rydberg gas. The narrowband laser excitation of Rydberg states in the range n = 20–80 from a 6 mK cloud of strontium atoms is detected using the spontaneous ionization of the Rydberg atoms. Using a high-resolution step-scanning technique, we perform detailed measurements of the Stark maps of selected Rydberg states. We find excellent agreement between the measured Stark maps and a numerical calculation based on an independent electron model. Finally we show that excitation of the second valence electron can be used to probe the dynamics of the Rydberg gas with nanosecond temporal resolution via autoionization

Modulation-free pump-probe spectroscopy of strontium atoms

We have performed polarization spectroscopy on the 5s21S0 →5s5p1P1 transition of atomic strontium. The signal is generated by saturation effects, rather than optical pumping, as the ground state is non-degenerate. This technique generated a dispersion-type lineshape suitable for laser stabilization, without the need for frequency modulation. The dependence of the amplitude and gradient on intensity and magnetic field were also investigated, and compared to a related technique based on the circular dichroism induced by a magnetic field

Medium-finesse optical cavity for the stabilization of Rydberg lasers

We describe the design, construction, and characterization of a medium-finesse Fabry-Perot cavity for simultaneous frequency stabilization of two lasers operating at 960 and 780 nm wavelengths, respectively. The lasers are applied in experiments with ultracold rubidium Rydberg atoms, for which a combined laser linewidth similar to the natural Rydberg linewidth (≈10 kHz) is desired. The cavity, with a finesse of ≈1500, is used to reduce the linewidth of the lasers to below this level. By using a spacer made of ultra low expansion (ULE) glass with active temperature stabilization, the residual frequency drift is limited to ≤1 MHz/day. The design optimizes for ease of construction, robustness, and affordability

Obtention de poudres spheriques et monodispersees de metaux precieux (Ag Pd en particulier) utilisables dans les composants electroniques et en microelectronique couche epaisse

Available from INIST (FR), Document Supply Service, under shelf-number : AR 16059 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEMinistere de la Recherche et de la Technologie (MRT), 75 - Paris (France)FRFranc

Rebels without a conscience: the evolution of the rogue states narrative in US security policy

This article examines how the foundations of the ‘rogue states’ security narrative in the United States developed prior to the declaration of the George W. Bush administration’s ‘Global War on Terror’ and President Bush’s representation of Iraq, Iran and North Korea as an ‘axis of evil’. The article argues that the puzzle of how US post-Cold War foreign and defence policy came to be focused on ‘irrational’ — but militarily inferior — adversaries can be understood through analysing how actors within the US defence community discursively constructed discrete international crises as the trigger for a major shift in US threat scenarios. This is developed through an examination of two crucial episodes in the construction of post-Cold War US national security interests: the crisis in the Persian Gulf in 1990–1 and the North Korean nuclear crisis in 1993–4. The article suggests the importance of historicizing contests over the interpretation of international crises in order to both better understand the process through which a country’s national security interests are defined and to gain greater analytical purchase on how security narratives are reconstructed during processes of systemic change