Beta-delayed neutron emission from93–100Rb to excited states in the residual Sr isotopes

Beta-delayed neutron emission from the precursors^93–100Rb to excited states in the residual nuclei^92–99Sr has been measured by means ofγ-ray and neutron spectroscopy. In general, considerable neutron feeding of excited final states is observed. The experimental branching ratios (P _n ⁱ ) are compared to predictions from statistical model calculations. It is demonstrated that the main parameter affecting theP _n ⁱ -values is the shape of theβ-strength function (S _β). For several Rb isotopes hindrance, respectively enhancement of neutron branches to specific final states is observed giving evidence for the persistence of intermediate structure of the neutron-emitting states. By the example of⁹⁸Rb it is shown that a few integralβ-delayed neutron properties may be sufficient to derive first estimates on the real shape ofS _β above the neutron binding energy. This result is of importance for exotic nuclei where detailed spectroscopic investigations are precluded.     

The beta-decay of95Rb and97Rb

In this paper the spectra ofα particles emitted in (p, α) reactions induced by ～24 MeV protons on adjacent target nuclei, onemagic, with a magic neutron or proton shell and the othernear magic, with one more nucleon outside the shell, are measured and compared. The nuclei investigated are^{90, 91}Zr,¹²²Sn,¹²³Sb,^{142, 143, 144}Nd,²⁰⁸Pb and²⁰⁹Bi. The weak population of low energy levels of the residual nucleus from thenear magic target nucleus and the excitation of homologous states in the residual nuclei from neighbouringmagic andnear magic target nuclei convincingly prove that in most of the cases the unpaired nucleon outside the magic shell acts as a spectator in the process. The implications of these experimental findings are discussed.     

Friction measurement in precision glass molding: An experimental study

Understanding the frictional behavior between glass and metals at elevated temperatures is necessary for accurate modeling and simulation of the state of the art applications such as the PGM process, pressing of micro lens arrays, hot embossing, and extrusion or drawing of glass fiber. In this research, the frictional behavior of N-BK7, an oxide glass, at elevated temperatures in contact with polished and coated tungsten carbide (WC) material and under conditions similar to the PGM process has been studied.The experimental results show that the friction coefficient between a polished and coated WC mold and N-BK7, which is a typical material for glass molding, and in conditions similar to those used in the PGM process ramps up to 0.7 and then levels off around 0.6 with a smooth transition, meaning that there is not a specific point to differentiate between static and dynamic friction. The friction coefficient of 0.6 is reported in literature for best fitting in micro lens molding simulation. Moreover, increasing the temperature in the transition regime in the mold/glass interface causes the friction force to increase which is in good agreement with the data published for the friction between soft polymeric material and metal in the transition regime.     

Intense mass-separated beams of halogens and beta-delayed neutron emission from heavy bromine isotopes

Improved production yields of short-lived halogens were obtained from a ThO₂ target, irradiated with 600 MeV protons, in combination with a negative surface ionization source. Mass-separated samples were studied by decay spectroscopy. Production yields of radioactive isotopes of chlorine, bromine, iodine and astatine are presented. Half-lives and relative neutron emission probabilities were measured for the heavy bromine isotopes^89?92Br. Normalizing to earlier publishedP _n values for⁸⁹Br, the results are:⁸⁹Br (4.30±0.14s,P _n =13.6±0.8%),⁹⁰Br (1.92±0.06s,P _n =24.8±1.5%),⁹¹Br (0.53 ±0.03 s,P _n =30.1 ±2.1%), and⁹²Br (0.31 ±0.02 s,P _n =34.6±2.5%). Energy spectra ofβ-delayed neutrons were measured.