Narrow Results

The nuclei ¹³¹I and ¹³³I have been populated in multi-nucleon transfer reactions between ¹³⁶Xe ions and various targets, and their structure investigated by time-correlated γ-ray coincidence spectroscopy and the measurement of γ-ray angular correlations. A 19/2^- isomer at 1918 keV, with a half-life of 24(1) µs, has been identified in ¹³¹I, as well as nanosecond isomers with J^π = 23/2⁺ in both isotopes. A T_1/2 = 25(3) ns isomer at 4308 keV in ¹³¹I is suggested to have J^π = (31/2^-, 33/2^-) and is primarily attributed to the coupling of an odd proton in the d_5/2 or g_7/2 orbit with the configuration in ¹³⁰Te, responsible for the 15^- isomer in that nucleus. The observed level properties are compared with predictions of a shell-model calculation.

Experiments based on the isomer-spectroscopy method were performed using the secondary beam line at RCNP, Osaka University. Recently, a new γ-ray spectroscopy method was established using fusion reaction induced by low-energy RI beam. This method enables us to study high-spin states of nuclei in wider mass region where it is difficult to populate them by using the combination of stable beams and stable targets. This method works well although low production of nuclei, because (1) the combination of beams and targets can be selected with large-reaction cross section and (2) high-S/N measurement can be performed by the event-by-event detection to select the events correlated with RI beam, which reduces background γ rays, competing with γ rays emitted from fusion products.

As the first step, high-spin states of ¹⁴²Pr were studied using fusion reaction induced by low-energy ¹⁷N RI beam. Large cross section was obtained by the ¹³⁰Te(¹⁷N,5n) reaction with 4.9 MeV/u ¹⁷N beam. Event selection, which was carried out by the event-by-event detection with low-beam intensity of 2×10⁴ pps, enables high-S/N measurement.

Quantum transport for different models of isomer molecules attached with two semi-infinite leads is studied on the basis of the Green's function technique. The electronic transport property is strongly affected by (a) the relative position of the atoms in these molecules and (b) the molecular coupling strength with the leads.

Excited states of ¹¹⁷Sn have been populated using the fusion-evaporation reaction ¹¹⁴Cd(⁷Li, 1p3n) at a beam energy of 48MeV. A total of nine new transitions have been identified and added into the level scheme of ¹¹⁷Sn. Based on the systematical comparisons with the neighboring Sn isotopes and the configuration-fixed constrained triaxial relativistic mean-field (RMF) calculations, a collective structure and two isomers are proposed to exist in ¹¹⁷Sn. The phenomenon of shape coexistence has been extended to A = 117 in odd-A Sn isotopes for the first time.

PCN and PNC are possible interstellar species that have not been experimentally characterized. With various ab initio methods, including multireference and restricted open-shell single-reference electronic structure theory, the PCN/PNC species and the transition state for the isomerization reaction PCN ↔ PNC have been studied. The Dunning series of correlation-consistent basis sets, cc-pVXZ and aug-cc-pVXZ (X = T and Q), have been used. Geometries, total energies, dipole moments, harmonic vibrational frequencies, infrared intensities, and zero-point vibrational energies are reported for the PCN/PNC isomers and the transition state. Both PCN and PNC are linear with ³Σ^- ground states, and linear is predicted to lie 13.7 kcal mol^-1 (13.5 kcal mol^-1 with ZPVE correction) above linear at the aug-cc-pVQZ CCSD(T) level of theory. The CN bond distance in is predicted to be 1.174 Å, only 0.002 Å longer than the experimental value of 1.172 Å for diatomic CN (X²Σ⁺, suggesting that CN has triple bond character in . The isomerization transition state is found to be cyclic , with angles θ_e (PCN) = 82.2°, θ_e (CNP) = 63.1°, and θ_e (NPC) = 34.7°. The isomerization barrier is predicted to be 35.7 kcal mol^-1 (34.5 kcal mol^-1 with ZPVE correction) relative to linear . The predicted dipole moments are substantial, 2.79 debye (polarity ⁺PCN^-) and 2.51 debye (polarity ⁺PNC^-).

The task to isolate metalloporphyrin compounds from crude oils is difficult, especially from reservoirs; the existence of well-known complexes homologous series type etioporphyrin (E), deoxophyloerythroetioporphyrin (DPEP), tetrahydrobenzodeoxoerythroetioporpyrin (THBD), benzoetio- porphyrin(BE) and benzodeoxoerythroetioporphyrin (BD) of vanadyl and nickel porphyrins, compounds found in crude oils around the world makes it hard. This includes natural porphyrins found in Mexican crude oils such as Ixtal-101, Zaap-1 and Ceh-1 from Sonda de Campeche, México, were the vanadyl porphyrins mixtures of the main series Etio and DPEP have also been reported elsewhere [14]. The objective of this investigation was to isolate porphyrins isomers from a single heavy crude oil from the Sonda de Campeche area, in México, and is based on the modified reversed-phase high-performance liquid chromatography method (RP-HPLC) [9, 11, 12]. Forty vanadyl porphyrin isomers, such as nickel porphyrin complexes were successfully isolated for the first time from heavy crude oil Zaap-1, through an exhaustive work which included a process of demetallization of vanadyl porphyrins to transmetallization to nickel porphyrins, in agreement with other methods [9, 11, 12, 14]. Further purification was achieved by thin-layer chromatography (TLC) with small glass chromatographic columns, packed with silica gel; then the purified isomers were analyzed and identified by electron impact mass spectrometry (EI-MS), providing the following results: from the Etio series seven isomers C₂₇E, C₂₈E, C₂₉E, C₃₀E, C₃₁E, C₃₂E, C₃₃E were identified. From DPEP series six isomers C₂₉D, C₃₀D, C₃₁D, C₃₂D, C₃₃D, C₃₄D were identified; from the BD series it was identified only 1 isomer of vanadyl from BD.

The electrical conduction of isomers of anthracene molecule attached between two semi-infinite gold electrodes was simulated using extended Huckel theory (EHT)-based on semi-empirical model in this research work. The electron transport parameters were examined in two epochs by buffering anthracene and its isomer phenanthrene alternatively between gold electrodes using sulphur as an alligator clip, under variegated bias voltages. Differential NDR effect was observed in both the cases but phenanthrene exhibited more linear I–V curve than its counterpart, anthracene. The simulated results discovered phenanthrene as a better candidate than anthracene towards contributing to electrical conduction in molecular junctions. Phenanthrene reported maximum conductance of 0.74G₀ whereas anthracene exhibited 0.03G₀ at 0.8V.

The stability of an organic compound depends on its nature and the environment in which it is placed. It depends on the presence or absence of reagents (acid, base, oxidizing agent, reducing agent, light, etc.) and catalysts. The stability may not be the same in the solid, liquid or gaseous state. In a homogenous solution, the stability might be affected by the polarity of the solvent and its concentration. For instance a polar solvent favors ionization. In a non-polar solvent ionization is difficult. In the gas phase ionization never occurs. In the gas phase and in solution stability depends on pressure and the presence of impurities. We are interested here in the thermal stability of pure compounds in the gas phase or in non-polar solvents under one atmosphere…

Neutron super-elastic scattering, also called neutron inelastic acceleration (INNA), occurs during the collision of a neutron with an excited nucleus. In this reaction, the nucleus could partly transfer its excitation energy to the scattered neutron. The effect of this neutron induced de-excitation is known in nuclear astrophysics to take place in the s-process nucleosynthesis.¹ Here, we report on the INNA cross section measurement, for the long-lived metastable state of ¹⁷⁷Lu, which was achieved using a direct method. High-energy neutrons have been detected using a specially designed setup placed on a cold neutron beam extracted from the ORPHEE reactor in Saclay. The measured value of 146±19 b for the INNA cross section in the ORPHEE cold neutron flux confirms the high cross section for this process on the ¹⁷⁷Lu^m isomer. The deviation from the 258±58 b previously published obtained for a Maxwellian neutron flux at a 323 K temperature, could be explained by the presence of a low energy resonance. Resonance parameters are deduced and discussed.