Investigation of 91Zr by high resolution (d, p), (p, p′) and (p, d) reactions

Abstract

Levels in the nucleus 40 91Zr 51 were studied by high resolution (d, p), (p, p′) and (p, d) reactions. Outgoing particles were momentum analysed using a split-pole spectrograph and detected by an array of four position sensitive solid state detectors coupled to an on-line computer. Overall resolutions ranged from 7 to 15 keV. Angular distributions obtained were compared to DWBA calculations. Optical model parameters were extracted from measured elastic angular distributions. The (d, p) and (p, d) experiments determined the distribution of the single particle and hole strength and were very helpful in making spin assignments. By a careful energy calibration discrepancies between some older measurements were resolved. In the (p, p′) reaction several states were excited that originate from the coupling of the 51st neutron to the 2 +, 5 −, 4 − and 3 − states of the 90Zr core. The present results clearly indicate that states with the Same spin and parity, but based on different core states, mix strongly with each other and with the singleparticle states, and that the simple weak coupling model can not be applied in this case. Some of the core excited states had non-negligible cross sections in the (d, p) reaction. CCBA calculations were able, in any case qualitatively, to describe the measured angular distributions of these states. Combining our results with those of γ-ray experiments a fairly complete picture of the levels of 91Zr below 3 Me V excitation energy has emerged.