The 153Sm nucleus: An experimental and theoretical study

The level structure of ¹⁵³Sm has been studied by means of the ¹⁵⁰Nd(α, n)¹⁵³Sm reaction. The experiment included measurements of the γ-γ coincidences and γ-ray yield as a function of projectile energy. The rotational band built on the $\text{11}\text{2}{}^{\mathrm{?}}$[505] Nilsson orbital was observed up to spin $\text{19}\text{2}$, and two ΔI = 2 bands of positive parity were identified with spins up to $\text{19}\text{2}\text{and}\text{21}\text{2}$, respectively. These bands are associated with the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ single-particle structure.The data obtained in the present work together with data available in the literature are compared to the result of a particle-rotor coupling calculation. The ¹⁵³Sm nucleus is found to be a wellbehaved rotor. An appropriate single-particle level scheme for ¹⁵³Sm is established.     

An investigation of the 144Sm(α, 3He)145Sm reaction

The ¹⁴⁴Sm(α, ³He)¹⁴⁵Sm stripping reaction has been studied up to 3 MeV excitation energy with a 40 MeV α-beam. Angular distributions have been recorded, and spectroscopic factors are deduced using a standard DWBA procedure. The reaction favours high-l transfers, and is found to be very useful for the investigation of large-j states. From a comparison with the spectroscopic factors known from the ¹⁴⁴Sm(d, p)¹⁴⁵Sm reaction the normalization factor for the (α, ³He) reaction is found to depend strongly on the optical model parameters and on the transferred angular momentum l.     

Hafnium decontamination from microquantities of some elements of groups I,II and III

A method for deep decontamination of high spin^178m2Hf isomer from microquantities of Sc, Fe, Co, Ni, Sb and Ag was elaborated using ion exchange separation on Dowex-1 in Hf and CH₃COOH–HCl media.     

Nuclear structure studies in the tellurium isotopes: the Te(d, p)Te reaction

The levels of ¹²⁷Te have been studied with the ¹²⁶Te(d, p)¹²⁷Te reaction at 7.5 MeV bombarding energy using the MIT multiple-gap broad-range magnetic spectrograph. A total number of 154 levels was observed below 5.7 MeV excitation energy. The angular distributions of 47 of the emitted proton groups were compared with DWBA stripping calculations to determine the orbital angular momentum of the captured neutrons. Transition strengths (2J+1)S_{ln, j} were extracted and compared to pairing-theory calculations. The total number of vacancies measured in the and states in the target is 6.0 , which is considerably lower than the expected value of 7.4 from pairing theory. It is suggested that this discrepancy results mainly from failure of the DWBA theory to predict the correct cross section for the l_n = 5 transition.     

A theoretical study of the effect of silicon substitution on hydrocarbon acidity

Ab initio molecular orbital calculations with double-zeta basis sets show the relative stabilities of three tautomers on the C₂SiH₄ energy hypersurface to be 3-silapropyne > 1-silaallene > 1-silapropyne. Comparison with literature values shows 1-silaallene to be more stable than 2-silaallene. Assuming deprotonation at carbon then the order of acidity is 1-silapropyne > 10-silaallene > 3-silapropyne > silaethane > silaethylene. For silaethylene and silaethane deprotonation occurs more easily at silicon than at carbon, while for both silapropynes and 1-silaallene carbon deprotonation is slightly favoured. The α-silyl group enhances the acidity of the adjacent methyl group and a silyl group in conjugation with a carboncarbon triple bond enhances the acidity of the alkynyl proton. The methyl, ethyl, and 2-silaethyl groups all weakly decrease the acidity of the alkynyl proton.     

A pH-responsive carboxylic β-1,3-glucan polysaccharide for complexation with polymeric guests

The helix-forming nature of β-1,3-glucan polysaccharides is a characteristic that has potential for producing gene carriers, bio-nanomaterials and other chiral nanowires. Herein, carboxylic curdlan (CurCOOH) bearing the β-1,3-polyglucuronic acid structure was successfully prepared from β-1,3-glucan polysaccharide curdlan (Cur) by one-step oxidation using a 4-acetamido-TEMPO/NaClO/NaClO(2) system as the oxidant. The resulting high-molecular-weight CurCOOH was proved to bear the 6-COOH group in 100% purity. The optical rotatory dispersion (ORD) spectra indicated that the obtained CurCOOH behaves as a water-soluble single-strand in various pH aqueous media. This advantage has allowed us to use CurCOOH as a polymeric host to form various macromolecular complexes. For example, complexation of CurCOOH with single-walled carbon nanotubes (SWNTs) resulted in a water-soluble one-dimensional architecture, which formed a dispersion in aqueous solution that was stable for several months, and much more stable than SWNTs complexes of the similar negatively-charged polyacrylic acid (PAA) and polymethacrylic acid (PMAA). It was shown that in the complex, SWNTs are effectively wrapped by a small amount of CurCOOH, enabling them to avoid electrostatic repulsion. This pH-responsive CurCOOH formed a very stable complex with cationic water-soluble polythiophenes (PT-1), which was stabilized not only by the hydrophobic interaction but also by the electrostatic attraction between trimethylammonium cations in PT-1 and dissociated anionic COO(-) groups in CurCOOH. The included PT-1 became CD-active only in the neutral to basic pH region, and the positive Cotton effect suggested that the conjugated main chain is twisted in the right-handed direction. We also found that CurCOOH can interact with polycytidylic acid (poly(C)) only under high NaCl concentrations, the binding and release of which could be controlled by a change in the salt concentration. We believe, therefore, that CurCOOH bearing a dissociable COOH group can act as a new potential polymeric host to construct novel polymeric complexes applicable for gene carriers, biosensors, chiral polymer assemblies, etc.     

Optical pulse-shaping for internal cooling of molecules

We consider the use of pulse-shaped broadband femtosecond lasers to optically cool rotational and vibrational degrees of freedom of molecules. Since this approach relies on cooling rotational and vibrational quanta by exciting an electronic transition, it is most easily applicable to molecules with similar ground and excited potential energy surfaces, such that the vibrational state is usually unchanged during electronic relaxation. Compared with schemes that cool rotations by exciting vibrations, this approach achieves internal cooling on the orders-of-magnitude faster electronic decay timescale and is potentially applicable to apolar molecules. For AlH(+), a candidate species, a rate-equation simulation indicates that rovibrational equilibrium should be achievable in 8 μs. In addition, we report laboratory demonstration of optical pulse shaping with sufficient resolution and power for rotational cooling of AlH(+).