Achievement of the planetary defense investigations of the Double Asteroid Redirection Test (DART) mission

NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 minutes, with two independent analysis methods each reporting a 1σ uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor, β, resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos–Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense

Single Crystal Growth of Cuprates from Hydroxide Fluxes

Barium and potassium hydroxide have been investigated as fluxes for the growth of cuprate single crystals. The relatively high solubility of transition metals and lanthanoids in these salt fluxes at moderate temperatures allows significant lowering of the growth temperatures required for many phases. Also, phases not stable at high temperatures become accessible. Two new cuprates have been prepared in the Ba-Ca-Cu-O and Ba-Y-Cu-O systems from a Ba(OH)2 · H2O flux. The compounds Ba3(Y0.23Cu0.77)2O5.78 and Ba3(Ca0.24Cu0.76)2O4.43 crystallize in a tetragonal (space group I4/mmm) oxygen deficient Sr3Ti2O7-type structure with lattice parameters a = 4.069(2) Å, 4.022(1) Å and c = 21.61(2) Å, 21.63(2) Å, respectively. The compound (Ba0.92Sr0.08)(Ca0.38Cu0.62)O 2.1 crystallizes with a doubled perovskite unit cell along all three axes, a = 8.116(4) Å. In addition, single crystals of Ba2YCu3O7-δ have been prepared from a KOH flux at 750 °C

Raman Spectroscopy of Single Crystals of High- Tc, Cuprates

We present normal mode assignments for the Raman spectra of 1-2-3-type materials on the basis of polarized Raman studies of single crystals of Ba2YCu3O7, Ba2YCu3O6, Sr2YCu2.4A10.607, and Ba2_xLaj+xCu3O7+δ. In Ba2YCu3O7 we observe five intrinsic modes at 500 [0(1) axial stretch], 435 [in-phase 0(2), 0(3) bend], 335 [out-of-phase 0(2), 0(3) bend], 140 [Cu(2) axial stretch mode], and 118 cm− 1(Ba axial mode). Defect-induced modes are found at 600 and 220 − 1. A mode at 640 − 1, which is seen only in ceramics, is shown to be due to a BaCuO2 impurity phase. Furthermore, we discuss the Raman spectra of Bi2Sr2Can − 1CunO4+2n, and the high-frequency (ω \u3e 1000 − 1) scattering in Ba2YCu3O6 and Ba2YCu3O7

A New Layered Cuprate Structure-Type, (A1-Xa′X)14Cu24O4 1

Phases crystallizing in a new structure-type with general formula (A1-xA′x)14Cu24O4 1 (A = alkaline earth metal, A′ = trivalent metal) and symmetry Cccm with an extended stoichiometry range have been found in studies of the SrYCuO, BaSrBiCuO and CaLaCuO systems. Single crystal X-ray studies on several crystals grown from different alkaline earth/metal oxide-cuprate melts reveal a common orthorhombic F-centered subcell of a=11.3 A ̊, b=13.0 A ̊ and c=3.9 A ̊. Superstructure is observed in crystals, leading to a 7-fold increase of the c-axis and a change in symmetry to space group Cccm. As in Ba2YCu3O7, the Cu atoms are found as CuO planes and linear CuO chains. Due to shear in the planes, half of the CuO squares share edges, producing CuCu zigzag chains, similar to the planes observed in CaCu2O3. In the linear CuO chains, the CuO squares share edges as well, leading to a short CuCu contact of 2.75Å. Experiments on ceramic samples indicate that the oxygen content is fixed and that the samples are semiconducting

Defect-Inhibited Incommensurate Distortion in Ta2NiSe7

We have observed evidence of an incommensurate structural distortion in the ternary chalcogenide Ta2NiSe7. The structure of Ta2NiSe7 is similar to FeNb3Se10 with one tantalum-centered trigonal prismatic chain and two inequivalent chains with octahedral coordination. Anomalies are observed in the resistance and magnetic susceptibility near 52.5 K. X-ray- and electron-diffraction data show the presence of an incommensurate modulation at temperatures below 52.5 K and strong diffuse scattering above 52.5 K. Hysteresis in the resistance and x-ray order parameter suggest that true long-range order of the lattice modulation is never achieved. We interpret the diffuse scattering as resulting from an inhibition of the phase transition caused by strong interactions between the lattice distortion and impurities or defects. Based on the transport data, we interpret the incommensurate structural distortion as being electronic in origin, a charge-density wave

Superconductivity in Lanthanum Barium Cuprate Perovskites

Samples in the system Ba2-xLa1+xCu3O7-δ (0.0 ≤ x ≤ 0.5; 0 \u3c δ \u3c 0.25) have been prepared and characterized by X-ray powder diffraction, magnetic susceptibility, electrical resistivity, and for x = 0.5 powder neutron diffraction. This neutron diffraction study on Ba1.5La1.5Cu3O7.25 indicates that the structure is similar to the 92 K superconductor Ba2YCu3O7 with two exceptions. First, the Ba site contains 75% Ba and 25% La and second, the symmetry is tetragonal. At x = 0.5 the material is a semiconductor, but as x decreases metallic behavior and superconductivity are observed. Compositions with x \u3c 0.2 contain traces of BaCuO2, but exhibit Tonsetc ≈ 90 K and R = 0 near 80 K. For x = 0.2-0.3, Tonsetc ≈ 60 K and R = 0 near 50 K are observed . For x ≤ 0.1 orthorhombic symmetry is observed. These results provide further evidence that oxygen stoichiometry and details of the oxygen ordering are important to superconductivity

The Structure and Properties of Ba2YCu3O6

The structure of Ba2YCu3O6 has been determined by neutron diffraction powder profile analysis. The cell is tetragonal P4/mmm with a=3.8570(1) A ̊ and c=11.8194(3) A ̊. The cations are in a perovskite type arrangement, with Ba and Y ordered on the A site to give a cell tripled along c. The oxygens occupy only 2 3 of the perovskite anion sites and are ordered such that 1 3 of the Cu is two-fold coordinated and 2 3 is five-fold coordinated. This configuration can be derived from that of the superconductor Ba2YCu3O7 by removing the oxygen atoms along the b axis at the ( 0,1 2,0) position. A pressed pellet exhibited semiconductivity with a band gap of 0.21eV from 125-300K. The compound is described as Ba2YCu1+Cu2+ 2O6