Natural Zr Research Articles

Mass dependence of π 0-production in heavy ion collisions at 1 A GeV

The production of neutral pions has been studied in the reactions 40 Ar+ nat Ca , 86 Kr+ nat Zr and 197 Au+ 197 Au at 1 A GeV. For high energy pions emitted from the heavier systems a steeper than linear rise of the pion multiplicity with the centrality of the reaction is observed, indicating a pion production process other than binary nucleon-nucleon collisions. At low transverse momenta an enhancement of the π 0-multiplicity increasing with the mass of the collision system is found. Systematic discrepancies between the experimental results and recent BUU, QMD and Cascade calculations are discussed.

The decay of mass-separated 99g, mAg

The decays of neutron-deficient 15 s 99Ag and 124 s 99gAg nuclides have been investigated at the Leuven Isotope Separator on-line facility. Sources were produced by the 92Mo( 14N, 2p5n) and nat Zr( 14 N, x n) reactions. Positron, conversion electron, X- and γ-ray singles spectra together with γ-γ coincidence measurements have been performed on mass-separated samples. The 1 2 − isomeric level in 99)Ag decays with a 163.6 keV isomeric transition to a 7 2 + level at 342.6 keV. Of the 106 γ-rays observed in the β + EC decay of the 99Ag ground state, 68 γ-rays (92 % of the γ-ray intensity) have been placed in a proposed level scheme. The relative variation of the J π = 9 2 + and 1 2 − levels in odd-mass Ag isotopes has been calculated using a residual proton-neutron delta interaction. The occurrence of decoupled bands in the odd Pd isotopes is discussed. Detailed calculations for 99Pd have been carried out in the framework of the Nilsson model (strong-coupling wave functions) using a strong Coriolis band mixing. Energy spectra for high-spin states, wave functions and low-lying non-yrast levels (below E x = 1 MeV) are also discussed.