.
New data on the production of single neutral pions in the
p
d
→
3
He
π
0
reaction are presented. For fifteen proton beam momenta between
p
p
=
1
.
60
GeV/
c
and
p
p
=
1
.
74
GeV/
c
, differential ...cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
New data on the production of single neutral pions in the pd -> He-3 pi(0) reaction are presented. For fifteen proton beam momenta between p(p) = 1.60GeV/c and p(p) = 1.74 GeV/c, differential ...cross sections are determined over a large fraction of the backward hemisphere. Since the only previous systematic measurements of single-pion production at these energies were made in collinear kinematics, the present work constitutes a significant extension of the current knowledge on this reaction. Even this far above the production threshold, significant changes are found in the behaviour of the angular distributions over small intervals in beam momentum.
The dayside atmospheres of ultra-hot Jupiters (UHJs) are predicted to possess temperature inversion layers with extremely high temperatures at high altitudes. We observed the dayside thermal emission ...spectra of WASP-18b and WASP-76b with the new CRIRES
+
high-resolution spectrograph at near-infrared wavelengths. Using the cross-correlation technique, we detected strong CO emission lines in both planets, which confirms the existence of temperature inversions on their dayside hemispheres. The two planets are the first UHJs orbiting F-type stars with CO emission lines detected; previous detections were mostly for UHJs orbiting A-type stars. Evidence of weak H
2
O emission signals is also found for both planets. We further applied forward-model retrievals on the detected CO lines and retrieved the temperature-pressure profiles along with the CO volume mixing ratios. The retrieved logarithmic CO mixing ratio of WASP-18b (−2.2
−1.5
+1.4
) is slightly higher than the value predicted by the self-consistent model assuming solar abundance. For WASP-76b, the retrieved CO mixing ratio (−3.6
−1.6
+1.8
) is broadly consistent with the value of solar abundance. In addition, we included the equatorial rotation velocity (
υ
eq
) in the retrieval when analyzing the line profile broadening. The obtained
υ
eq
is 7.0 ± 2.9 km s
−1
for WASP-18b and 5.2
−3.0
+2.5
km s
−1
for WASP-76b, which are consistent with the tidally locked rotational velocities.
The density functional theory (DFT) method has been used to calculate oxygen adsorption on the Ag-doped MnO
2
- and LaO-terminated (001) LaMnO
3
surfaces. The catalytic effect of Ag doping is ...revealed by comparison of the adsorption energies, electron charge redistribution, and interatomic distances for the doped and undoped surfaces. Adsorption of Ag on the MnO
2
-terminated surface increases the adsorption energy for both atomic and molecular oxygen. This increases the oxygen surface concentrations and could improve the cathode efficiency of fuel cells. The opposite effect takes place at the LaO-terminated surface. Due to the large adsorption energies, adsorbed oxygen atoms are immobile and the oxygen reduction reaction rate is controlled by the concentration and mobility of oxygen vacancies.
Context. It is generally agreed upon that stars form in open clusters (OCs) and stellar associations, but little is known about structures in the Galactic OC population; whether OCs and stellar ...associations are born isolated or if they prefer to form in groups, for example. Answering this question provides new insight into star and cluster formation, along with a better understanding of Galactic structures. Aims. In the past decade, studies of OC groupings have either been based solely on spatial criteria or have also included tangential velocities for identifications. In contrast to previous approaches, we assumed that real OC groupings occupy a well defined area in the sky and show similar velocity vectors. For the first time, we have used 6D phase-space information, including radial velocities from the RAdial Velocity Experiment (RAVE) and other catalogues, for the detection of OC groupings. We also checked the age spread of potential candidates to distinguish between genuine groupings and chance alignments. Methods. We explored the Catalogue of Open Cluster Data (COCD) and determined 6D phase-space information for 432 out of 650 listed OCs and compact associations. The group identification was performed using an adapted version of the Friends-of-Friends algorithm, as used in cosmology, with linking lengths of 100 pc and 10-20 km s super(-1). For the verification of the identified structures, we applied Monte Carlo simulations with randomised samples. Results. For the linking lengths 100 pc and 10 km s super(-1), we detected 19 groupings, including 14 pairs, 4 groups with 3-5 members, and 1 complex with 15 members. The Monte Carlo simulations revealed that, in particular, the complex is most likely genuine, whereas pairs are more likely chance alignments. A closer look at the age spread of the complex and the comparison between spatial distributions of young and old cluster populations suggested that OC groupings likely originated from a common molecular cloud.
Metal tris-
o
-dioxolene (
o-
quinone,
o-
semiquinone, and catecholate) complexes represent an interesting and vivid model system for the demonstration of a relationship between the structure and ...magnetic properties when considering a series of objects of the same type. After publishing the reviews 1, 2, the metal tris-
o-
dioxolene complexes containing the symmetric 3,6-di-
tert
-butyl-
o-
benzoquinone derivatives with substituents in positions 4 and 5 are described in a number of works. In addition, some earlier unpublished structures of the complexes of this type are reviewed. The substituents in the lateral chains enhance the steric protection of the metal center and, as a consequence, result in the formation of coordination polyhedra uncharacteristic of the tris(dioxolene) complexes, such as a trigonal prism. In turn, the distortion of the structure affects the magnetic properties of the complexes. Only the complexes with the derivatives of sterically hindered
o-
quinones, 3,5- and 3,6-di-
tert
-butyl-
o-
benzoquinones, are considered in the present review. On the one hand, bulky
tert
-butyl groups prevent the formation of direct intermolecular contacts and, on the other hand, prevent organic reactions to occur at the benzoquinone cycle.
Context. A subclass of the upper main-sequence chemically peculiar stars, mercury-manganese (HgMn) stars were traditionally considered to be non-magnetic, showing no evidence of variability in their ...spectral line profiles. However, discoveries of chemical inhomogeneities on their surfaces imply that this assumption should be investigated. In particular, spectroscopic time-series of AR Aur, α And, and five other HgMn stars indicate the presence of chemical spots. At the same time, no signatures of global magnetic fields have been detected. Aims. We attempt to understand the physical mechanism that causes the formation of chemical spots in HgMn stars and gain insight into the potential magnetic field properties at their surfaces; we performed a highly sensitive search for magnetic fields for a large set of HgMn stars. Methods. With the aid of a new polarimeter attached to the HARPS spectrometer at the ESO 3.6 m-telescope, we obtained high-quality circular polarization spectra of 41 single and double HgMn stars. Using a multi-line analysis technique on each star, we co-added information from hundreds of spectral lines to ensure significantly greater sensitivity to the presence of magnetic fields, including very weak fields. Results. For the 47 individual objects studied, including six components of SB2 systems, we do not detect any magnetic fields at greater than the 3σ level. The lack of detection in the circular polarization profiles indicates that if strong fields are present on these stars, they must have complex surface topologies. For simple global fields, our detection limits imply upper limits to the fields present of 2−10 Gauss in the best cases. Conclusions. We conclude that HgMn stars lack large-scale magnetic fields, which is typical of spotted magnetic Ap stars, of sufficient strength to form and sustain the chemical spots observed on HgMn stars. Our study confirms that in addition to magnetically altered atomic diffusion, there exists another differentiation mechanism operating in the atmospheres of late-B main sequence stars that can produce compositional inhomogeneities on their surfaces.
The
o
-iminobenzoquinone complexes of lanthanum, samarium, and ytterbium, Ln(L)
3
(L = 3,5-ditert- butyl-1,2-quinone-1-(2-oxy-3,5-di-tert-butylphenyl)imine) are synthesized. In order to study the ...photovoltaic properties of the obtained complexes and previously synthesized similar complexes of zinc and aluminum M(L)
2
prototypes of photovoltaic cells are prepared on their basis. An examination of the fabricated devices has revealed that nanolayers of all the compounds, except for ytterbium complex, exhibited photovoltaic properties. The best results of energy conversion are achieved for single-layer cells containing zinc complex as a photoactive material (Open-circuit voltage
U
OC
= 1.01 V, short-circuit current
J
SC
= 5.2 nA/cm
2
).
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