16 research outputs found
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 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 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) 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 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
Ă GĂȘnes, un exemple Ă suivre
Dans lâancien port de GĂȘnes se trouve depuis vingt ans La CittĂ dei Bambini e dei Ragazzi, nĂ©e dâune collaboration avec la CitĂ© des enfants de La Villette.
Plus de 3000 m2 pour captiver, Ă©merveiller les 2-13 ans par des rencontres actives et variĂ©es avec les sciences et les technologies. Les installations laissent la part belle Ă lâinitiative et Ă la dĂ©couverte individuelle dans lâamusement et le jeu, Ă lâaide dâoutils Ă©ducatifs et de diffusion scientifique qui privilĂ©gient la manipulation, lâobservation et lâexpĂ©rience directe, mais aussi la « gestion » du doute. Toute une stratĂ©gie permettant aux enfants dâaller au-delĂ des acquis scolaires, en proposant une participation active sur des thĂšmes 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 prĂ©sente la synthĂšse des rĂ©sultats dâune enquĂȘte de la SFP auprĂšs de ses adhĂ©rents, sur la culture scientifique dans la sociĂ©tĂ© française. Elle fait suite Ă une tribune sur ce sujet, parue en fĂ©vrier 2018 dans le Huffington Post.
La publication des rĂ©sultats de cette enquĂȘte a Ă©tĂ© plusieurs fois reportĂ©e, pour des raisons techniques et Ă©ditoriales. Cette publication est donc trĂšs tardive, mais ses rĂ©sultats quant Ă la perception de lâimportance et du rĂŽle de la culture scientifique dans notre sociĂ©tĂ© et au sein de la SFP restent dâactualitĂ©