On the discrepancies in the low energy neutron-deuteron breakup

In view of recent neutron-deuteron (nd) breakup data for neutron-neutron (nn) and neutron-proton (np) quasi-free-scattering (QFS) arrangements and the large discrepancy found between theoretical predictions and measured nn QFS cross sections, we analyze the sensitivity of the QFS cross sections to different partial wave components of the nucleon-nucleon (NN) interaction. We found that the QFS cross section is strongly dominated by the 1S0 and 3S1-3D1 contributions. Because the standard three-nucleon force (3NF) only weakly influence the QFS region, we conjecture, that it must be the nn 1S0 force component which is responsible for the discrepancy in the nn QFS peak. A stronger 1S0 nn force is required to bring theory and data into agreement. Such an increased strength of the nn interaction will, however, not help to explain the nd breakup symmetric-space-star (SST) discrepancy. Further experimental cross-checkings are required.Comment: 17 pages, 10 figure

Circular and Folded Multi-Spin Strings in Spin Chain Sigma Models

From the SU(2) spin chain sigma model at the one-loop and two-loop orders we recover the classical circular string solution with two S^5 spins (J_1, J_2) in the AdS_5 x S^5 string theory. In the SL(2) sector of the one-loop spin chain sigma model we explicitly construct a solution which corresponds to the folded string solution with one AdS_5 spin S and one S^5 spin J. In the one-loop general sigma model we demonstrate that there exists a solution which reproduces the energy of the circular constant-radii string solution with three spins (S_1, S_2, J).Comment: 16 pages, LaTeX, no figure

Time Resolved Photoelectron Spectroscopy of Thioflavin T Photoisomerization: A Simulation Study

The excited state isomerization of thioflavin T (ThT) is responsible for the quenching of its fluorescence in a non-restricted environment. The fluorescence quantum yield increases substantially upon binding to amyloid fibers. Simulations reveal that the variation of the twisting angle between benzothiazole and benzene groups (ϕ(1)) is responsible for the sub-picosecond fluorescence quenching. The evolution of the twisting process can be directly probed by photoelectron emission with energies ε ≥ 1.0 eV before the molecule reaches the ϕ(1)-twisted configuration (~300 fs)

X-RAY ABSORPTION STUDIES OF MIXED-VALENT RARE EARTH CLUSTERS

The transition from atomic to metallic valences in small matrixisolated clusters of Sm, Nd and Pr has been studied by XANES- and EXAFS-measurements at the corresponding L3-edges. The observed valence of the Rare Earth clusters depends on the atomic concentrations and on the type of metal atom. Hints on the cluster size are given by annealing the samples to temperatures near the melting point of the Rare Gas matrix. In Nd and Pr samples a complete valence change from 2 to 3 has been observed within an atomic concentration range of 0.1 to 0.25 % metal content. Clusters containing more than 4 - 6 atoms are totally trivalent. For Sm a valence transition is observed at 1 % metal concentration, the valence rising from 2.0 to 2.6. From EXAFS data a critical cluster size of K = 13 atoms at v = 2.6 has been elaborated. Sm clusters with K > 13 are mixed valent

Critical cluster size for mixed valence in small matrix-isolated Sm clusters

From L3 absorption measurement, information on the valence and size of small matrix-isolated Sm clusters is obtained by analyzing the x-ray-absorption near-edge structure and the extended x-ray-absorption fine structure (EXAFS). Depending on the mean cluster size, which is a function of the atomic concentration (Sm to rare-gas atom ratio), every valence between 2.0 and 3.0 is reproducibly achievable. At very low Sm concentrations the samples have the atomic valence; at a critical concentration c≊1:100 a steep rise of the valence up to v=2.6 is found. Then, with increasing metal concentration, the Sm-cluster valence approaches the valence of the solid. From EXAFS analysis, a mean cluster size of 13 atoms for clusters with v=2.6 follows. The mixed valence of the Sm atoms is explained by the pressure exerted on the Sm cluster by the distorted rare-gas lattice (the rare gas is Ne, Ar, or Kr)

Excited-state dynamics of guanosine in aqueous solution revealed by time-resolved photoelectron spectroscopy: experiment and theory

Time-resolved photoelectron spectroscopy is performed on aqueous guanosine solution to study its excited-state relaxation dynamics. Experimental results are complemented by surface hopping dynamic simulations and evaluation of the excited-state ionization energy by Koopmans' theorem. Two alternative models for the relaxation dynamics are discussed. The experimentally observed excited-state lifetime is about 2.5 ps if the molecule is excited at 266 nm and about 1.1 ps if the molecule is excited at 238 nm. The experimental probe photon energy dependence of the photoelectron kinetic energy distribution suggests that the probe step is not vertical and involves a doubly-excited autoionizing state