Comment on "Prospect of optical frequency standard based on a 43Ca+ ion"

A recent evaluation of the frequency uncertainty expected for an optical frequency standard based on a single trapped $^{43}$Ca$^+$ ion was published in Phys. Rev. A {\bf 72} (2005) 043404. The paper contains some interesting information like systematic frequency shifts but fails to depict their uncertainty, leading to confuse accuracy and precision. The conclusions about the major contribution to the frequency shift are not consistent with the presented calculations and omit comparisons with data published previously

Long-term stabilization of the length of an optical reference cavity

To obtain a high degree of long-term length stabilisation of an optical reference cavity, its free-spectral range is locked by means of an accurate and stable frequency synthesizer. The locking scheme is twofold: a laser is locked on the N$^{th}$ mode of a reference Fabry-Perot cavity and part of the laser light is shifted in frequency to be in resonance with the (N+1)$^{th}$ mode of the cavity. This shift is generated by an acousto-optical modulator (AOM) mounted in a double-pass scheme, matching half of the free spectral range of the reference cavity. The resulting absolute stabilization of the length of the cavity reaches the 10$^{-11}$ level per second, limited by the lock transfer properties and the frequency stability of the AOM control synthesizer

Metastable level lifetimes from electron-shelving measurements with ion clouds and single ions

The lifetime of the 3d^2D_5/2-level in singly-ionized calcium has been measured by the electron-shelving technique on different samples of rf trapped ions. The metastable state has been directly populated by exciting the dipole-forbidden 4S_1/2 - 3D_5/2 transition. In ion clouds, the natural lifetime of this metastable level has been measured to be (1095+-27) ms. For the single-ion case, we determined a lifetime of (1152+-20) ms. The 1sigma-error bars at the 2%-level have different origins for the two kinds of experiments: data fitting methods for lifetime measurements in an ion cloud and control of experimental parameters for a single ion. De-shelving effects are extensively discussed. The influence of differing approaches for the processing of the single-ion quantum jump data on the lifetime values is shown. Comparison with recent measurements shows excellent agreement when evaluated from a given method

à Gênes, un exemple à suivre

Dans l’ancien port de Gênes se trouve depuis vingt ans La Città dei Bambini e dei Ragazzi, née d’une collaboration avec la Cité des enfants de La Villette. Plus de 3000 m2 pour captiver, émerveiller les 2-13 ans par des rencontres actives et variées avec les sciences et les technologies. Les installations laissent la part belle à l’initiative et à la découverte individuelle dans l’amusement et le jeu, à l’aide d’outils éducatifs et de diffusion scientifique qui privilégient la manipulation, l’observation et l’expérience directe, mais aussi la « gestion » du doute. Toute une stratégie permettant aux enfants d’aller au-delà des acquis scolaires, en proposant une participation active sur des thèmes concrets et attrayants

Investigation of a Ca+ rf stored ion cloud and observation of the forbidden S-D transitions,

International audienceno abstrac

Collisional quenching and j-mixing rate constants for the 3 D levels of Ca+

International audienceno abstrac

Collisional quenching and j-mixing rate constants for the 3 D levels of Ca+

International audienceno abstrac

Investigation of a Ca+ rf stored ion cloud and observation of the forbidden S-D transitions,

International audienceno abstrac

Les membres de la Société Française de Physique et la culture scientifique

Cet article présente la synthèse des résultats d’une enquête de la SFP auprès de ses adhérents, sur la culture scientifique dans la société française. Elle fait suite à une tribune sur ce sujet, parue en février 2018 dans le Huffington Post. La publication des résultats de cette enquête a été plusieurs fois reportée, pour des raisons techniques et éditoriales. Cette publication est donc très tardive, mais ses résultats quant à la perception de l’importance et du rôle de la culture scientifique dans notre société et au sein de la SFP restent d’actualité