PRESSURE BROADENING AND SHIFTING COEFFICIENTS AS TESTS OF H2(D2)-He POTENTIAL ENERGY SURFACES

International audienceWe have calculated the helium-pressure broadening and shifting coefficients of the isotropic Raman Q(1) lines of the fundamental of H 2 and D 2. The quantum dynamical close coupling calculations were performed on five 3-dimensional PESs, namely: the pot3d potential of Bakr et al, 1 the so-called BMP PES, 2 the modified Muchnik and Russek PES, 3 the modified BMP PES, 1 and the Schaefer and Köhler PES. 4 The last one being the oldest one and obtained at the lowest-level of quantum chemical accuracy but has the advantage of covering interactions over a larger intramolecular interval. Moreover, the theoretical values it leads to 5,6,7 are in quite good agreement with experimental pressure broadening and shifting coeffients. 7,8,9,10 By decomposing the kinetic energy dependent pressure broadening cross-sections in an inelastic part and a dephasing one and by also looking at the isotropic contribution of the pressure shifting cross-sections allow us to bring to the fore the main differences that exist between the five PESs we have considered. The modBMP PES has been readily rejected because it is only a slight modification of the original BMP PES. The BMP and modMR PESs lead to thermally averaged values far from the experimental ones. The quantum chemical " state of the art " PES of Bakr et al provides shifting parameters in better agreement than the SK PES with experimental shifts but, the broadening parameters seem to be slightly more accurate with the SK PES. This last point should be confirmed by an accu-

Narrow Line Photoassociation in an Optical Lattice

With ultracold $^{88}$Sr in a 1D magic wavelength optical lattice, we performed narrow line photoassociation spectroscopy near the $^1$S$_0 - ^3$P$_1$ intercombination transition. Nine least-bound vibrational molecular levels associated with the long-range $0_u$ and $1_u$ potential energy surfaces were measured and identified. A simple theoretical model accurately describes the level positions and treats the effects of the lattice confinement on the line shapes. The measured resonance strengths show that optical tuning of the ground state scattering length should be possible without significant atom loss.Comment: 4 pages, 4 figure

High-resolution MCP-TimePix3 imaging/timing detector for antimatter physics

We present a hybrid imaging/timing detector for force sensitive inertial measurements designed for measurements on positronium, the metastable bound state of an electron and a positron, but also suitable for applications involving other low intensity, low energy beams of neutral (antimatter)-atoms, such as antihydrogen. The performance of the prototype detector was evaluated with a tunable low energy positron beam, resulting in a spatial resolution of approximate t

Guidelines for developing optical clocks with 10-18 fractional frequency uncertainty

There has been tremendous progress in the performance of optical frequency standards since the first proposals to carry out precision spectroscopy on trapped, single ions in the 1970s. The estimated fractional frequency uncertainty of today's leading optical standards is currently in the 10−18 range, approximately two orders of magnitude better than that of the best caesium primary frequency standards. This exceptional accuracy and stability is resulting in a growing number of research groups developing optical clocks. While good review papers covering the topic already exist, more practical guidelines are needed as a complement. The purpose of this document is therefore to provide technical guidance for researchers starting in the field of optical clocks. The target audience includes national metrology institutes (NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD students and postdocs entering the field. Another potential audience is academic groups with experience in atomic physics and atom or ion trapping, but with less experience of time and frequency metrology and optical clock requirements. These guidelines have arisen from the scope of the EMPIR project "Optical clocks with 1×10−18 uncertainty" (OC18). Therefore, the examples are from European laboratories even though similar work is carried out all over the world. The goal of OC18 was to push the development of optical clocks by improving each of the necessary subsystems: ultrastable lasers, neutral-atom and single-ion traps, and interrogation techniques. This document shares the knowledge acquired by the OC18 project consortium and gives practical guidance on each of these aspects.EU/Horizon2020/EMPIR/E

Collisional-Broadened and Dicke-Narrowed Lineshapes of H216O and H218O Transitions at 1.39 μm

We present results of a study on the self-broadening and broadening by nitrogen and oxygen of H(2)(16)O and H(2)(18)O lines in the 1.39-µm wavelength region using a distributed feedback semiconductor diode laser. To estimate the broadening coefficients, the absorption lineshapes were analyzed using the ordinary Voigt profile which provided good fits for most of the investigated lines. The broadening coefficients were found to be larger for nitrogen used as a perturber than for oxygen. This agrees with the fact that the quadrupole moment of N(2) is larger than that of O(2). Nevertheless, for lines involving high-rotational quantum number J, relatively smaller broadening coefficients were found and deviations of the measured profiles from the standard Voigt profile were observed. These deviations were ascribed as caused by Dicke-narrowing effect. Corresponding to this effect, collisional-broadening and narrowing coefficients were determined using the Nelkin-Ghatak profile which is suitable for the "hard"-collision model. The optical diffusion coefficients of the water in both nitrogen and oxygen gases were determined from the measurements of the collisional-narrowing coefficients. Copyright 2001 Academic Press