Role of magnetic and orbital ordering at the metal-insulator transition in NdNiO3

Soft x-ray resonant scattering at the Ni L2,3 edges is used to test models of magnetic and orbital-ordering below the metal-insulator transition in NdNiO3. The large branching ratio of the L3 to L2 intensities of the (1/2,0,1/2) reflection and the observed azimuthal angle and polarization dependence originates from a non collinear magnetic structure. The absence of an orbital signal and the non collinear magnetic structure show that the nickelates are materials for which orbital ordering is absent at the metal-insulator transition.Comment: 10 pages, 4 figures, Physical Review B rapid communication, to be publishe

Study of Bº→D*-π+π-π+ and Bº→D*-K+π-π+ decays

Using proton-proton collision data collected by the LHCb experiment at √s=7  TeV, corresponding to an integrated luminosity of 1.0  fb-1, the ratio of branching fractions of the Bº→D*-π+π-π+ decay relative to the Bº→D*-π+ decay is measured to be B(Bº→D*-π+π-π+)/B(Bº→D*-π+)=2.64±0.04(stat)±0.13(syst). The Cabibbo-suppressed decay Bº→D*-K+π-π+ is observed for the first time, and the measured ratio of branching fractions is B(Bº→D*-K+π-π+)/B(Bº→D*-π+π-π+)=(6.47±0.37(stat)±0.35(syst))×10-2. A search for orbital excitations of charm mesons contributing to the Bº→D*-π+π-π+ final state is also performed, and the first observation of the Bº→D- 1(2420)0π+π- decay is reported with the ratio of branching fractions B(B0→(D- 1(2420)0→D*-π+)π-π+)/B(B0→D*-π+π-π+)=(2.04±0.42(stat)±0.22(syst))×10-2, where the numerator represents a product of the branching fractions B(B0→D- 1(2420)0π-π+) and B(D- 1(2420)0→D*-π+)

Vibrational state dependence of ionic rotational branching ratios in resonance enhanced multiphoton ionization of CH

We show that rapid evolution of a Rydberg orbital with internuclear distance in a resonance enhanced multiphoton ionization (REMPI) process can have a profound influence on the production of molecular ions in alternative rotational states. This is illustrated by calculations of ionic rotational branching ratios for (2+1′) REMPI via the O11 (20.5) branch of the E′ ^2Σ^+(3pσ) Rydberg state of CH. The rotational propensity rule for ionization changes from ΔN=odd (ΔN=N_+−N_i) at lower vibrational excitation, as expected from the ΔN+l=odd selection rule, to ΔN=even at higher vibrational levels. This effect is expected to be quite general and should be most readily observable in diatomic hydrides

High-velocity stars from the interaction of a globular cluster and a massive black hole binary

High-velocity stars are usually thought to be the dynamical product of the interaction of binary systems with supermassive black holes. In this paper, we investigate a particular mechanism of production of high-velocity stars as due to the close interaction between a massive and orbitally decayed globular cluster and a supermassive black hole binary. The high velocity acquired by some stars of the cluster comes from combined effect of extraction of their gravitational binding energy and from the slingshot due to the interaction with the black hole binary. After the close interaction, stars could reach a velocity sufficient to travel in the halo and even overcome the galactic potential well, while some of them are just stripped from the globular cluster and start orbiting around the galactic centre

Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method

The newly developed nonadiabatic method based on the coupled-channel Schroedinger equation with Gamow states is used to study the phenomenon of proton radioactivity. The new method, adopting the weak coupling regime of the particle-plus-rotor model, allows for the inclusion of excitations in the daughter nucleus. This can lead to rather different predictions for lifetimes and branching ratios as compared to the standard adiabatic approximation corresponding to the strong coupling scheme. Calculations are performed for several experimentally seen, non-spherical nuclei beyond the proton dripline. By comparing theory and experiment, we are able to characterize the angular momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure

Rotationally resolved photoelectron angular distributions in resonance enhanced multiphoton ionization of NO

We report calculated ionic rotational branching ratios and associated photoelectron angular distributions for (1+1′) resonance enhanced multiphoton ionization (REMPI) via the R_(21)(20.5), P_(21)+Q_(11)(25.5), and P_(11)(22.5) branches of the A ^2 Σ^+(3sσ) state of NO. The branching ratios are dominated by even angular momentum transfer peaks, in agreement with the ΔN+l=odd (ΔN≡N+−Ni ) selection rule. Whereas the calculated photoelectron angular distributions are very branch dependent alignment, the ionic branching ratios are found to be less so. The present calculated results agree well with the experimental results of Allendorf et al