No Arabic abstract
Using density functional theory, we investigate the structure of mixed $^3$He$_{N_3}$-$^4$He$_{N_4}$ droplets with an embedded impurity (Xe atom or HCN molecule) which pins a quantized vortex line. We find that the dopant+vortex+$^4$He$_{N_4}$ complex, which in a previous work [F. Dalfovo {it et al.}, Phys. Rev. Lett. {bf 85}, 1028 (2000)] was found to be energetically stable below a critical size $N_{rm cr}$, is robust against the addition of $^3$He. While $^3$He atoms are distributed along the vortex line and on the surface of the $^4$He drop, the impurity is mostly coated by $^4$He atoms. Results for $N_4=500$ and a number of $^3$He atoms ranging from 0 to 100 are presented, and the binding energy of the dopant to the vortex line is determined.
We present static and dynamical properties of linear vortices in 4He droplets obtained from Density Functional calculations. By comparing the adsorption properties of different atomic impurities embedded in pure droplets and in droplets where a quantized vortex has been created, we suggest that Ca atoms should be the dopant of choice to detect vortices by means of spectroscopic experiments.
We discuss the stability of homonuclear and heteronuclear mixtures of 3He and 4He atoms in the metastable 2^3S_1 state (He*) and predict positions and widths of Feshbach resonances by using the Asymptotic Bound-state Model (ABM). All calculations are performed without fit parameters, using emph{ab-initio} calculations of molecular potentials. One promising very broad Feshbach resonance (Delta B=72.9^{+18.3}_{-19.3} mT) is found that allows for tuning of the inter-isotope scattering length.
A propagation torsion model for quantized vortices is proposed.The model is applied to superfluids and liquid Helium II.
Surface waves on both superfluid 3He and 4He were examined with the premise, that these inviscid media would represent ideal realizations for this fluid dynamics problem. The work on 3He is one of the first of its kind, but on 4He it was possible to produce much more complete set of data for meaningful comparison with theoretical models. Most measurements were performed at the zero temperature limit, meaning T < 100 mK for 4He and T ~ 100 {mu}K for 3He. Dozens of surface wave resonances, including up to 11 overtones, were observed and monitored as the liquid depth in the cell was varied. Despite of the wealth of data, perfect agreement with the constructed theoretical models could not be achieved.
The strong-interaction shift of kaonic 3He and 4He 2p states was measured using gaseous targets for the first time in the SIDDHARTA experiment. The determined shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70s and 80s. Thus, the problems in kaonic helium (the kaonic helium puzzle) was definitely solved by our measurements. The first observation of the kaonic 3He X-rays was also achieved. The shift both of kaonic 3He and 4He was found to be as small as a few eV.