High-spin states in Au-188: Further evidence for nonaxial shape

The high-spin level structure of Au-188 has been investigated via the Yb-173(F-19,4n gamma) reaction at beam energies of 86 and 90 MeV. The previously reported level scheme has been modified and extended significantly. A new I-pi = 20(+) state associated with pi h(11/2)(-1) circle times nu i(13/2)(-2)h(9/2)(-1) configuration and two new rotational bands, one of which is built on the pi h(9/2) circle times nu i(13/2) configuration, have been identified. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around Au-188 for the pi h(9/2) circle times nu i(13/2) bands in odd-odd Au isotopes. Evidence for pi h(11/2)(-1) circle times nu i(13/2)(-1) structure of nonaxial shape with gamma < -70 degrees has been obtained by comparison with total Routhian surface and cranked-shell-model calculations.

Identification of a quasiparticle band in very neutron-rich Zr-104

The high spin levels of a very neutron-rich Zr-104 nucleus have been reinvestigated by measuring the prompt. rays in the spontaneous fission of Cf-252. The ground-state band has been confirmed. A new sideband has been identified with a band-head energy at 1928.7 keV. The projected shell model is employed to investigate the band structure of Zr-104. The results of calculated levels are in good agreement with the experimental data, and suggest that the new band in Zr-104 may be based on the neutron nu 5/2(-)[532] circle times nu 3/2(+)[411] configuration.

Dipole bands in nucleus Pm-139

High-spin states in nucleus Pm-139 have been studied using the reaction Cd-116(Al-27, 4n)Pm-139. Two dipole cascades have been found. Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei (DCO) ratios and systematic behavior in neighboring odd-proton nuclei. The level structures of Pm-139 are compared with those of the N = 78 isotone Eu-141 in which two dipole bands have been confirmed as magnetic rotational bands. The close similarity between them suggests that the dipole bands in Pm-139 may be magnetic rotational bands.

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.

Band properties of the transitional nucleus Pt-189

High-spin states in Pt-189 have been studied with the in-beam gamma-spectroscopy method via the Yb-176(O-18, 5n) reaction at beam energies of 88 MeV and 95 MeV. A new level scheme of Pt-189 has been established. Rotational bands based on the upsilon i(13/2)(-1), upsilon f(5/2)(p(3/2)) and upsilon i(13/2)(-2)upsilon f(p(3/2)) configurations, as well as several structures with irregular level spacings, have been observed. Properties of rotational bands have been analyzed in the framework of triaxial particle-rotor model. A gamma similar to -30 degrees triaxial shape and a near prolate shape have been proposed to the upsilon i(13/2)(-1) and uf(5/2)(p(3/2)) bands, respectively. Two Delta I=2 transition sequences with similar energies have been observed, and they have been proposed to be associated with the upsilon i(13/2)(-1)upsilon f(5/2)(p(3/2)) configuration. According to the relevant Nilsson orbitals, the bands built on the upsilon i(13/2)(-1)upsilon f(5/2)(p(3/2)) configuration could be interpreted as a pair of pseudo-spin partner.

Analytical potential energy function and spectroscopic parameters for the ground and excited states of NaH

set of energies at different internuclear distances for the ground electronic state and two excited electronic states of NaH molecule have been calculated using valence internally contracted multireference configuration interaction(MRCI) including Davidson correction and three basis sets. Then, a potential energy curve (PEC) for each state was determined by extrapolating MRCI energies to the complete basis sets limit. Based on the PECs, accurate vibrational energy levels and rotational constants were determined. The computational PECs are were fitted to analytical potential energy functions using the Murrell-Sorbie potential function. Then, accurate spectroscopic parameters were calculated. Compared with experimental results, values obtained with the basis set extrapolation yield a potential energy curve that gives accurate vibrational energy levels, rotational constants and spectroscopic parameters for the NaH molecule. (C) 2004 Elsevier B.V. All rights reserved.

Photodissociation dynamics of the methyl radical at 212.5 nm: Effect of parent internal excitation

Photodissociation dynamics of the CH3 radical at 212.5 nm has been investigated using the H atom Rydberg tagging time-of-flight method with a pure CH3 radical source generated by the photolysis of CH3I at 266 nm. Time-of-flight spectra of the H atom products from the photolysis of both cold and hot methyl radicals have been measured at different photolysis polarizations. Experimental results indicate that the photodissociation of the methyl radical in its ground vibrational state at 212.5 nm excitation occurs on a very fast time scale in comparison with its rotational period, indicating the CH3 dissociation at 212.5 nm occurs on the excited 3s Rydberg state surface. Experimental evidence also shows that the photodissociation of the methyl radical in the nu(2)=1 state of the umbrella mode at 212.5 nm excitation is characteristically different from that in the ground vibrational state. (C) 2004 American Institute of Physics.

State-to-state dynamics of elementary chemical reactions using Rydberg H-atom translational spectroscopy

In this review, a few examples of state-to-state dynamics studies of both unimolecular and bimolecular reactions using the H-atom Rydberg tagging TOF technique were presented. From the H2O photodissociation at 157 nm, a direction dissociation example is provided, while photodissociation of H2O at 121.6 has provided an excellent dynamical case of complicated, yet direct dissociation process through conical intersections. The studies of the O(D-1) + H-2 --> OH+H reaction has also been reviewed here. A prototype example of state-to-state dynamics of pure insertion chemical reaction is provided. Effect of the reagent rotational excitation and the isotope effect on the dynamics of this reaction have also been investigated. The detailed mechanism for abstraction channel in this reaction has also been closely studied. The experimental investigations of the simplest chemical reaction, the H-3 system, have also been described here. Through extensive collaborations between theory and experiment, the mechanism for forward scattering product at high collision energies for the H+HD reaction was clarified, which is attributed to a slow down mechanism on the top of a quantized barrier transition state. Oscillations in the product quantum state resolved different cross sections have also been observed in the H+D-2 reaction, and were attributed to the interference of adiabatic transition state pathways from detailed theoretical analysis. The results reviewed here clearly show the significant advances we have made in the studies of the state-to-state molecular reaction dynamics.

The shape parameter of Liposomes and DNA-lipid complexes determined by viscometry utilizing small sample volumes

A minicapillary viscometer utilizing <0.5 ml of sample at a volume fraction of <0.1% is described. The calculated a/b of DPPC/DPPG multilamellar liposome was 1.14 as prolate ellipsoids and a/b of dioleoylpropyltrimethyl ammonium methylsulfate-DNA complex at a charge ratio of 4: 1 (+/-) was 3.7 as prolate ellipsoids or 4.9 as oblate ellipsoids. The deviation of shape from perfect sphere is thus expressed quantitatively in more than two significant figures. In these measurement, the necessary amount of DNA is <0.5 mg.

Theoretical studies of product polarization and state distributions of the H+HCl reaction

The angular momentum polarization and rotational state distributions of the H-2 and HCl products from the H + HCl reaction are calculated at a relative translational energy of 1.6 eV by using quasiclassical trajectories on two potential energy surfaces, one from G3 surface [T.C. Allison et al., J. Phys. Chem. 100 (1996) 13575], and the other from BW2 surface [W. Bian, H.-J. Werner, J. Chem. Phys. 112 (2000) 220]. Product rotational distributions obtained on the G3 potential energy surface (PES) are much closer to the experimental results (P.M. Aker et al., J. Chem. Phys. 90 (1989) 4795; J. Chem. Phys. 90 (1989) 4809) than the distributions calculated on the BW2 PES. The distributions of P(phi(r)) for the H-2 and HCl products obtained on the G3 PES are similar, whereas the rotational alignment effect of the H-2 product is stronger than that of the HCl product. In contrast to the polarization distributions obtained on the G3 PES, the rotational alignment effect of the two products calculated on the BW2 PES is similar. However, the abstraction reaction is dominated by out-of-plane mechanisms, while the exchange reaction is dominated by in-plane mechanisms. The significant difference of the product rotational polarization obtained on the G3 and BW2 PESs implies that the studies of the dynamical stereochemistry can provide a sensitive test for the accuracy of the PES. (C) 2002 Elsevier Science B.V. All rights reserved.

The rheological behavior and dynamic mechanical properties of syndiotactic 1,2-polybutadiene

The rheological behavior and the dynamic mechanical properties of syndiotactic 1,2-polybutadiene (sPB) were investigated by a rotational rheometer (MCR-300) and a dynamic mechanical analyzer (DMA-242C). Rheological behavior of sPB-830, a sPB with crystalline degree of 20.1% and syndiotactic content of 65.1%, showed that storage modulus (G ') and loss modulus (G '') decreased, and the zero shear viscosity (eta(0)) decreased slightly with increasing temperature when measuring temperatures were lower than 160 degrees C. However, G ' and G '' increased at the end region of relaxation curves with increasing temperature and)10 increased with increasing temperature as the measuring temperatures were higher than 160 degrees C. Furthermore, critical crosslinked reaction temperature was detected at about 160 degrees C for sPB-830. The crosslinked reaction was not detected when test temperature was lower than 150 degrees C for measuring the dynamic mechanical properties of sample. The relationship between processing temperature and crosslinked reaction was proposed for the sPB-830 sample.

Electronic structures and chemical bonding in 4d transition metal monohalides

Bond distances, vibrational frequencies, dipole moments, dissociation energies, electron affinities, and ionization potentials of NIX (XM = Y-Cd, X = F, Cl, Br, I) molecules in neutral, positively, and negatively charged ions were studied by density functional method, B3LYP. The bonding patterns were analyzed and compared with both the available data and across the series. It was found that besides ionic component, covalent bonds are formed between the 4d transition metal s, d orbitals, and the p orbital of halogen. For both neutral and charged molecules, the fluorides have the shortest bond distance, iodides the longest. Although the opposite situation is observed for vibrational frequency, that is, fluorides have the largest value, iodides the smallest. For neutral and anionic species, the dissociation energy tends to decrease with the increasing atomic number from Y to Cd, suggesting the decreasing or weakening of the bond strength. For cationic species, the trend is observed from Y to Ag.

Analysis of interfacial phenomena of aqueous solutions of polyethylene oxide and polyethylene glycol flowing in hydrophilic and hydrophobic capillary viscometers

Viscosities of aqueous solutions of five polyethylene oxide (PEO) samples with molar masses from 1.5 x 10(5) to 1.0 x 10(6) were carefully measured in a polytetrafluoroethylene (PTFE) capillary Ubbelohde viscometer in the concentration range from dilute down to extremely dilute concentration regions and compared with those of the same sample obtained from a glass capillary viscometer. At the same time, viscosities of aqueous solutions of three PEG samples in glass and paraffin-coated capillary viscosity were measured. The wall effects occurred in viscosity measurements for PEO and PEG aqueous solutions in different capillary viscometers were theoretically analyzed and discussed. It was found that different interfacial behaviors occurred in both hydrophobic and hydrophilic capillary viscometers respectively and the interfacial behaviors also exhibit molar mass dependence.

Electronic structures of 3d-metal mononitrides

Bond distances, vibrational frequencies, electron affinities, ionization potentials, and dissociation energies of the title molecules in neutral, positively, and negatively charged ions were studied by use of density functional methods B3LYP, BLYP, BHLYP, BPW91, and B3PW91. The calculated results are compared with experiments and previous theoretical studies. It was found that the calculated properties are highly dependent on the functionals employed, in particular for the dissociation energy and vibrational frequency. For neutral species, pure density functional methods BLYP and BPW91 have relatively good performance in reproducing the experimental bond distance and vibrational frequency. For cations, hybrid exchange functional methods B3LYP and B3PW91 are good in predicting the dissociation energy. For both neutral and charged species, BHLYP tends to give smaller dissociation energy.

Functionalization of an ethylene-propylene copolymer with allyl (3-isocyanate-4-tolyl) carbamate

An ethylene-propylene copolymer (EPM) was functionalized with an iso cyanate-bearing unsaturated monomer, allyl(3-isocyanate-4-tolyl) carbamate (TAI), with dicumyl peroxide as an initiator in a xylene solution. Fourier transform infrared (FTIR) was used to confirm the formation of EPM-g-TAI. The peak at 2273 cm(-1), characteristic of -NCO groups in EPM-g-TAI, revealed evidence of grafting. The grafting degree was determined with both chemical titration and FTIR. The grafting degree could be adjusted, and the maximum was over 6 wt % without any gelation. The molar mass distribution of EPM-g-TAI was narrower than that of EPM. The rheological behavior of both EPM-g-TAI and EPM was investigated with a rotational rheometer. The apparent viscosity of EPM-g-TAI was higher than that of EPM and increased with an increasing grafting degree of TAI. Surface analysis by contact-angle measurements showed that contact angles of EPM-g-TAI samples to a given polar liquid decreased with an increasing grafting degree of TAI. We also obtained the dispersion component of the surface free energy (gamma(S)(d)), the polar component of the surface free energy (gamma(S)(d)), and the total surface free energy (gamma(S) = gamma(S)(d) + gamma(S)(p)) of the grafted EPM. These parameters increased with the enhancement of the grafting degree, which gave us a quantitative estimation of the polar contribution of the grafted TAI to the total surface free energy of EPM-g-TAI.