Photoionization of propargyl and bromopropargyl radicals: a threshold photoelectron spectroscopic study

In this Article, we present mass-selected threshold photoelectron spectra of propargyl as well as the 1- and 3-bromopropargyl radicals. The reactive intermediates were produced by flash pyrolysis of suitable precursors and ionized by VUV synchrotron radiation. The TPES of the propargyl radical was simulated using data from a recent high-level computational study. An ionization energy (IE) of 8.71 ± 0.02 eV was obtained, in excellent agreement with computations, but slightly above previous experimental IEs. The pyrolysis of 1,3-dibromopropyne delivers both 1- and 3-bromopropargyl radicals that can be distinguished by their different ionization energies (8.34 and 8.16 eV). To explain the vibrational structure, a Franck-Condon simulation was performed, based on DFT calculations, which can account for all major spectral features. Bromopropargyl photoionizes dissociatively beginning at around 10.1 eV. Cationic excited states of 1- and 3-bromopropargyl were tentatively identified. The dissociative photoionization of the precursor (1,3-dibromopropyne) was also examined, delivering an AE(0K) (C(3)H(2)Br(+)/C(3)H(2)Br(2)) of 10.6 eV.     

Selected ion flow tube study of ion-molecule reactions of N(+)(3P) and Kr+ with C3 hydrocarbons propane, propene, and propyne

Reactions of (14)N(+)((3)P), (15)N(+)((3)P), and Kr(+) with propane, propene, and propyne were studied using the selected ion flow tube, SIFT, technique. Thermal rate constants in all N(+)/C(3) systems were k = (2 ± 0.4) × 10(-9) cm(3) molecule(-1) s(-1), close to the collisional rate constants. With propane and propene, only hydrocarbon ions were found among the products of reactions with N(+); in propyne about 15% of the products were N-containing ions (C(3)H(2)N(+), C(2)H(4)N(+), C(2)H(3)N(+), C(2)H(2)N(+)), and the rest were hydrocarbon ions. A comparison with product ions from electron transfer between Kr(+) (of recombination energy similar to that for N(+)((3)P)) and the C(3) hydrocarbons and further analysis of the results led to an estimation of an approximate ratio of electron transfer vs hydride-ion transfer reactions leading to the hydrocarbon product ions: in propane the ratio was 2:1, in propene 3:1, and in propyne 5:1. A fraction of product ions resulted from reactions leading to the excited neutral product N*.     

A study on 210Po activity concentration in soil at different depths along coastal Kerala

The paper presents systematic studies on the vertical profiles of ²¹⁰Po, an important decay product of ²³⁸U, in soils along coastal Kerala. Soil samples collected from different depth intervals 0–10, 10–20, 20–30 cm were analyzed for ²¹⁰Po activity concentration by radiochemical methods. The activity ²¹⁰Po in soil samples were counted using a ZnS(Ag) alpha scintillation counting system. The mean values of activity concentrations of ²¹⁰Po in soil of various depths were found to be 8.66, 5.63 and 4.95 Bq kg⁻¹ for depth intervals of 0–10, 10–20 and 20–30 cm, respectively. The overall activity concentration of ²¹⁰Po in soil was found to vary from 2.26 ± 0.19 to 14.02 ± 0.12 Bq kg⁻¹ with a mean value of 6.43 Bq kg⁻¹. Maximum activity concentration was found in soil samples of Kollam region with the mean value of 10.08 ± 0.92 Bq kg⁻¹. The activity of ²¹⁰Po was found to be comparatively high in surface soil. The variation of ²¹⁰Po activity concentration with organic matter contents was studied. ²¹⁰Polonium activity concentration was found to increase with increasing organic matter content.     

A Spectroscopic Validation of the Improved Lennard–Jones Model

The Lennard–Jones (LJ) and Improved Lennard–Jones (ILJ) potential models have been deeply tested on the most accurate CCSD(T)/CBS electronic energies calculated for some weakly bound prototype systems. These results are important to plan the correct application of such models to systems at increasing complexity. CCSD(T)/CBS ground state electronic energies were determined for 21 diatomic systems composed by the combination of the noble gas atoms. These potentials were employed to calculate the rovibrational spectroscopic constants, and the results show that for 20 of the 21 pairs the ILJ predictions agree more effectively with the experimental data than those of the LJ model. The CCSD(T)/CBS energies were also used to determine the β parameter of the ILJ form, related to the softness/hardness of the interacting partners and controlling the shape of the potential well. This information supports the experimental finding that suggests the adoption of β≈9 for most of the systems involving noble gas atoms. The He-Ne and He-Ar molecules have a lifetime of less than 1ps in the 200–500 K temperature range, indicating that they are not considered stable under thermal conditions of gaseous bulks. Furthermore, the controversy concerning the presence of a “virtual” or a “real” vibrational state in the He2 molecule is discussed.     

Host–guest system of 4-nerolidylcatechol in 2-hydroxypropyl-β-cyclodextrin: preparation, characterization and molecular modeling

The interaction of 4-nerolidylcatechol (4-NRC), a potent antioxidant agent, and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated by the solubility method using Fourier transform infrared (FTIR) methods in addition to UV–Vis, ¹H-nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. The inclusion complexes were prepared using grinding, kneading and freeze-drying methods. According to phase solubility studies in water a B_S-type diagram was found, displaying a stoichiometry complexation of 2:1 (drug:host) and stability constant of 6494 ± 837 M^?1. Stoichiometry was established by the UV spectrophotometer using Job’s plot method and, also confirmed by molecular modeling. Data from ¹H-NMR, and FTIR, experiments also provided formation evidence of an inclusion complex between 4-NRC and HP-β-CD. 4-NRC complexation indeed led to higher drug solubility and stability which could probably be useful to improve its biological properties and make it available to oral administration and topical formulations.     

Renormalization for piecewise smooth homeomorphisms on the circle

In this work we study the renormalization operator acting on piecewise smooth homeomorphisms on the circle, that turns out to be essentially the study of Rauzy–Veech renormalizations of generalized interval exchange maps with genus one. In particular we show that renormalizations of such maps with zero mean nonlinearity and satisfying certain smoothness and combinatorial assumptions converge to the set of piecewise affine interval exchange maps.     

Multi-magnetic phases in Fe1−xNixTa2O6

X-ray, neutron diffraction and magnetic susceptibility are reported for Fe_xNi_1−xTa₂O₆ mixed oxides. X-ray refinement indicates homogeneous samples for all the reported concentrations. The neutron-diffraction measurements reveal magnetic structures with double propagation vectors. This system exhibits at least two bicritical points at about x=0.15 and 0.60. For these concentrations, at low temperatures, the system shows the coexistence of two magnetic structures. This bicritical behaviour is interpreted as induced by competition between the different magnetic structures.     

Quasiprobability and Probability Distributions for Spin-1/2 States

We develop a Radon-like transformation, in which P quasiprobability distribution for spin-1/2 states is written in terms of the tomographic probability distribution w.