Simple device for dissolution and sample transfer for applications in spin-hyperpolarization

ABSTRACT

Rapid dissolution and transfer of samples are crucial steps in hyperpolarization methods such as dissolution dynamic nuclear polarization (dDNP) and quantum-rotor-induced polarization (QRIP). Here we introduce a simple and modular dissolution transfer device, and we demonstrate its application for QRIP. This device operates with low pressures and solvent volumes compared to state-of-the-art dDNP setups. On the other hand, transfer times are longer, although sufficient for ¹³C NMR spectroscopy. Our approach does not require an additional cryostat.     

Extrinsic symplectic symmetric spaces

We define the notion of extrinsic symplectic symmetric spaces and exhibit some of their properties. We construct large families of examples and show how they fit in the perspective of a complete classification of these manifolds. We also build a natural ?$?$-quantization on a class of examples.     

High pressure studies on Fe-pnictide superconductors

A review of high pressure studies on Fe-pnictide superconductors is given. The pressure effects on the magnetic and superconducting transitions are discussed for different classes of doped and undoped FeAs-compounds: ROFeAs (R = rare-earth), AeFe₂As₂ (Ae = Ca, Sr, Ba), and AFeAs (A = Li, Na). Pressure tends to decrease the magnetic transition temperature in the undoped or only slightly doped compounds. The superconducting T_c increases with low pressure for underdoped FeAs-pnictides, remains approximately constant for optimal doping, and decreases linearly in the overdoped range. The undoped LaOFeAs and AeFe₂As₂ become superconducting under pressure although non-hydrostatic pressure condition seems to play a role in CaFe₂As₂. The superconductivity in the (undoped) AFeAs is explained as a chemical pressure effect due to the volume contraction caused by the small ionic size of the A-elements. The binary FeSe shows the largest pressure coefficient of T_c in the Se-deficient superconducting phase.     

Superconducting Fe-based compounds (A1-xSrx)Fe2As2 with A=K and Cs with transition temperatures up to 37 K

New high-T{c} Fe-based superconducting compounds, AFe2As2 with A=K, Cs, K/Sr, and Cs/Sr, were synthesized. The T{c} of KFe2As2 and CsFe2As2 is 3.8 and 2.6 K, respectively, which rises with partial substitution of Sr for K and Cs and peaks at 37 K for 50%-60% Sr substitution, and the compounds enter a spin-density-wave state with increasing electron number (Sr content). The compounds represent p-type analogs of the n-doped rare-earth oxypnictide superconductors. Their electronic and structural behavior demonstrate the crucial role of the (Fe2As2) layers in the superconductivity of the Fe-based layered systems, and the special feature of having elemental A layers provides new avenues to superconductivity at higher T{c}.     

Absence of fermionic quasiparticles in the superfluid state of the attractive fermi gas

We calculate the effect of order parameter fluctuations on the fermionic single-particle excitations in the superfluid state of neutral fermions interacting with short-range attractive forces. We show that in dimensions D< or =3 the singular effective interaction between the fermions mediated by the gapless Bogoliubov-Anderson mode prohibits the existence of well-defined quasiparticles. We explicitly calculate the single-particle spectral function in the BEC regime in D=3 and show that in this case the quasiparticle residue and the density of states are logarithmically suppressed.     

Observation of strongly deformed ground-state configurations in184Au and183Au by laser spectroscopy

Resonance ionization mass spectroscopy (RIMS) and pulsed-laser induced desorption (PLID) have been combined in order to study the isotope shift (IS) and hyperfine structure (HFS) of¹⁸⁴Au (T_1/2=53 s) and¹⁸³Au (T_1/2=42 s) in the 6s²S_1/2 → 6p²P_1/2 (λ=267 nm) transition. The Au isotopes were obtained as daughters in the decay of^184,183Hg produced and mass separated at the new ISOLDE-3 facility at CERN. It was found that the strong deformationβ ₂}-0.25 setting in at¹⁸⁶Au persists down to¹⁸³Au.     

α-particle break-up in the interaction with protons at 8.6 GeV/c 4He momentum

Helium break-up reactions have been studied in ⁴He-proton interactions at 8.6 GeV/c⁴He momentum in the hydrogen bubble chamber. Total and differential cross sections for different reaction channels without pion production have been measured. The results have been compared with multiple scattering model predictions.     

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