Nuclear orbiting and anomalies in nuclear reactions

In this paper, we report our measurements of back-angle oxygen and carbon particle yields from ¹⁶O+⁸⁹Y, ¹²C+⁹³Nb reactions forming the same compound nucleus ¹⁰⁵Ag at the same excitation energy and spin distribution. We find anomalously large oxygen yield and entrance channel dependence at high excitation energies from ¹⁶O+⁸⁹Y reaction implying formation of a dinuclear orbiting complex. Possible connection between nuclear orbiting and fast fission is also discussed.     

Towards advanced chemical and biological nanosensors-An overview

This paper reviews recent developments in the design and application of two types of optical nanosensor, those based on: (1) localized surface plasmon resonance (LSPR) spectroscopy and (2) surface-enhanced Raman scattering (SERS). The performance of these sensors is discussed in the context of biological and chemical sensing. The first section addresses the LSPR sensors. Arrays of nanotriangles were evaluated and characterized using realistic protein/ligand interactions. Isolated, single nanoparticles were used for chemosensing and performed comparably to the nanoparticle array sensors. In particular, we highlight the effect of nanoparticle morphology on sensing response. The second section details the use of SERS sensors using metal film over nanosphere (MFON) surfaces. The high SERS enhancements and long-term stability of MFONs were exploited in order to develop SERS-based sensors for two important target molecules: a Bacillus anthracis biomarker and glucose in a serum protein mixture.     

Polymerization of aromatic nuclei. XVIII. Polymerization of benzene to poly-p-phenylene by aluminum chloride–air–water

Although the reaction of benzene with aluminum chloride has been quite thoroughly examined by prior investigators, the present report is the first one on formation of poly-p-phenylene in this system. Optimum conditions, which gave low yields, involved 7 days at 49–51deg;C. The presence of oxygen (oxidant) and presumably water (cocatalyst) was necessary in order for polymerization to occur. Physical and chemical properties, e.g., behavior toward Br₂ and H₂O₂–CH₃CO₂H, indicate that the polymer structure is slightly different from that of the material from C₆H₆–AlCl₃–CuCl₂. The polymer from C₆H₆–AlCl₃ may possess a lower molecular weight and exhibits a greater degree of structural irregularity in the form of dihydrobenzene, p-quinoid, or polynuclear regions. In the chemical studies, various compounds were used as models (tetrahydroquaterphenyl, triphenylene, and lower p-polyphenyls).     

Analysis of key steps in the catalytic cross-coupling of alkyl electrophiles under Negishi-like conditions

The use of tpy'(tpy'= 4,4',4'-tri-tert-butyl-terpyridine) as a ligand for nickel allows for the isolation of a Ni(I)-alkyl complex and a Ni(II)-alkyl halide complex, both of which can be used as mechanistic probes of key steps in alkyl cross-coupling reactions.     

Self-assembly of CdSe/CdS quantum dots by hydrogen bonding on Au surfaces for photoreception

CdSe/CdS core-shell quantum dots have been self-assembled onto thiolcarboxylic acid functionalized gold surfaces by hydrogen bonding; control of the pH during deposition allows producing a high coverage photoactive surface for use in a surface sensitized Schottky barrier photovoltaic structure.     

Syntheses, structure, some band gaps, and electronic structures of CsLnZnTe3 (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y)

Eleven new quaternary rare-earth tellurides, CsLnZnTe3 (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Y), were prepared from solid-state reactions at 1123 K. These isostructural materials crystallize in the layered KZrCuS3 structure type in the orthorhombic space group Cmcm. The structure is composed of LnTe6 octahedra and ZnTe4 tetrahedra that share edges to form [LnZnTe3] layers. These layers stack perpendicular to [010] and are separated by layers of face- and edge-sharing CsTe8 bicapped trigonal prisms. There are no Te-Te bonds in the structure of these CsLnZnTe3 compounds so the formal oxidation states of Cs/Ln/Zn/Te are 1+/3+/2+/2-. Optical band gaps of 2.13 eV for CsGdZnTe3 and 2.12 eV for CsTbZnTe3 were deduced from single-crystal optical absorption measurements. A first-principles calculation of the density of states and the frequency-dependent optical properties was performed on CsGdZnTe3. The calculated band gap of 2.1 eV is in good agreement with the experimental value. A quadratic fit for the lanthanide contraction of the Ln-Te distance is superior to a linear one if the closed-shell atom is included.     

The CsLnMSe3 semiconductors (Ln = rare-earth element,Y; M = Zn,Cd, Hg)

CsLnCdSe(3) (Ln = Ce, Pr, Sm, Gd, Tb, Dy, Y) and CsLnHgSe(3) (Ln = La, Ce, Pr, Nd, Sm, Gd, Y) have been synthesized at 1123 K. These isostructural materials crystallize in the layered KZrCuS(3) structure type in the orthorhombic space group Cmcm and are group X extensions of the previously characterized Zn compounds. The structure is composed of two-dimensional [LnMSe(3)] layers that stack perpendicular to [010] and are separated by layers of face- and edge-sharing CsSe(8) bicapped trigonal prisms. Because there are no Se-Se bonds in the structure of CsLnMSe(3) (M = Zn, Cd, Hg), the formal oxidation states of Cs/Ln/M/Se are 1+/3+/2+/2-. CsSmHgSe(3) does not adhere to the Curie-Weiss law, whereas CsCeHgSe(3) and CsGdHgSe(3) are Curie-Weiss paramagnets with micro (eff) values of 2.77 and 7.90 micro (B), corresponding well with the theoretical values of 2.54 and 7.94 micro (B) for Ce(3+) and Gd(3+), respectively. Single-crystal optical absorption measurements were performed with polarized light perpendicular to the (010) and (001) crystal faces of these materials. The band gaps of the (010) crystal faces range from 1.94 eV (CsCeHgSe(3)) to 2.58 eV (CsYCdSe(3)) whereas those of the (001) crystal faces span the range 2.37 eV (CsSmHgSe(3)) to 2.54 eV (CsYCdSe(3) and CsYHgSe(3)). The largest band gap variation between crystal faces is 0.06 eV for CsYCdSe(3). Theoretical calculations for CsYMSe(3) indicate that these materials are direct band gap semiconductors whose colors and optical band gaps are dependent upon the orbitals of Y, M, and Se.     

Measurement of the ground state 2n pickup probability for 28Si+68Zn and its role in sub-barrier fusion enhancement

The ground state and excited state transfer yields for the 2-neutron pickup channel in the ²⁸Si+⁶⁸Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV.     

Fission fragment angular distributions in 16O+181Ta

Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model.