New Experiments With Spheres-Gas (NEWS-G) is a direct dark matter detection experiment using SphericalProportional Counters (SPCs) with light noble gases to search for low-mass Weakly Interacting Massive Particles (WIMPs). We report the results from the first physics run taken at the Laboratoire Souterrain de Modane (LSM) with SEDINE, a 60 cm diameter prototype SPC operated with a mixture of Ne + CH 4 (0.7 %) at 3.1 bars for a total exposure of 9.7 kg · days. New constraints are set on the spin-independent WIMP-nucleon scattering cross-section in the sub-GeV/c 2 mass region. We exclude cross-sections above 4.4 × 10 −37 cm 2 at 90 % confidence level (C.L.) for a 0.5 GeV/c 2 WIMP. The competitive results obtained with SEDINE are promising for the next phase of the NEWS-G experiment: a 140 cm diameter SPC to be installed at SNOLAB by summer 2018.

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Spherical Proportional Counters (SPCs) are a novel gaseous detector technology employed by the NEWS-G low-mass dark matter search experiment for their high sensitivity to single electrons from ionization. In this paper, we report on the first characterization of the single electron response of SPCs with unprecedented precision, using a UV-laser calibration system. The experimental approach and analysis methodology are presented along with various direct applications for the upcoming next phase of the experiment at SNOLAB. These include the continuous monitoring of the detector response and electron drift properties during dark matter search runs, as well as the experimental measurement of the trigger threshold efficiency. We measure a mean ionization energy of W = 27.6 ± 0.2 eV in Ne + CH4 (2%) for 2.8 keV X-rays, and demonstrate the feasibility of performing similar precision measurements at sub-keV energies for future gas mixtures to be used for dark matter searches at SNOLAB.

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Nickel(II) phosphine complexes are prepared with a series of diphenylalkenylphosphine ligands and characterised by single crystal X-ray diffraction and spectroscopic techniques.

The solution chemistry of cobalt(II) ketophosphine complexes CoXztPhaPCHaCCOlPhJz (la, X = Cl; lb, X = Br; le, X = I) has been examined and compared to that of [CoX2(PPh3)2] (2a, X = Cl; 2b, X = Br; 2c, X = I). All the complexes undergo a tetrahedral-octahedral equilibrium in methanol. This is facilitated by solvent coordination rather than by the ligand's keto functions. Some degree of ligand displacement also occurs. The crystal structure of la has been elucidated, showing a pseudotetrahedral cobalt(II) geometry. A long interligand hydrogen-bond, not present in powder samples, is observed between the methylene group of a Ph2PCH2C(0)Ph ligand and the ketone function of the other Ph2PCH2C(0)Ph ligand, la reacts with Na[Co(CO)4] to afford the crystallographically characterized, metal-metal bonded centrosymmetric complex C02(CO)6[Ph2PCH2C(O)Ph]2 (5) (Co-Co = 2.666-(1) Á). The reactivity of la with AgBF4 and T1PF6 has also been examined and compared to that of 2a where the latter is reacted in the presence and absence of excess phosphine. Notable reaction products include the square i-1 planar cobalt(II) complex [Co{Ph2PCH2C(0)Ph}{Ph2PCH2C( 0)Ph}Cl]PF6 ( 6), which slowly transforms in solution I-1 to the octahedral complex [Co{Ph2PCH2C(0)Ph}2{Ph2PCH2C( 0)Ph}Cl] PFe (7). Reaction with AgBF4 under similar conditions affords the silver phosphine complex Ag{Ph2PCH2C(0)Ph}2Cl (8). 2a reacts with AgBF4 to give [Ag-(PPh3)2]BF4, but additionally in the presence of PPh3 gives (Ph3P)2Ag(#t-Cl)2Co(/t-Cl)2Ag(PPh3)2 ( 13). The latter formulation involving a central C0CI42-core, and an almost linear Ag-Co-Ag arrangement has been confirmed by single-crystal X-ray diffraction. The solid state structures of la, 5, and 13 .50 12 have been determined by single-crystal X-ray analysis, la crystallizes in the monoclinic space group P2\/c with Z = 4 in a unit cell of dimensions a = 10.985(2) k,b = 17.236(4) Á, c = 19.547(4) Á, and ß = 104.87(2)°.