Stretched high-spin two-neutron-hole states in 206Pb and 114Sn via the (p,t) reaction at 168 MeV.

Abstract

Two-neutron-hole excitations have been investigated via the(/ital p/,/ital t/) reaction at 168 MeV on /sup 208/Pb and/sup 116/Sn targets, up to /similar to/25 and /similar to/17 MeVexcitation energy, respectively. The kinematic conditions strongly favor high/ital L/ transfer values (/ital L//similar to/10 for Sn and /ital L//similar to/13 for Pb).High-spin stretched states are found to dominate the spectra with an evenstronger enhancement for/ital J/=((/ital l//sub 1/+(1/2)(l/sub 2//minus/1)/2))/sub /ital J//sub max// states.Angular distributions and standardlocal zero-range distorted-wave Born approximation analysis have been performedfor /sup 206/Pb. Such analysis has been extended to the/sup 114/Sn data taken at two angles. The zero-range normalizationconstant /ital D//sub 0//sup 2/ is found to be significantly smaller thanthat usually adopted at low incident energy, /ital D//sub 0//sup 2//similar to/6instead of /similar to/22. The high-spin stretched states of the valencemultiplets are distributed from 2.2 MeV up to 6.1 MeV in/sup 206/Pb, whereas they are clustered between /similar to/3.0and 3.7 MeV in /sup 114/Sn. New spectroscopic information gainedfor /ital J//sup ..pi../greater than or equal to6 levels or structures in /sup 206/Pb and/sup 114/Sn is discussed together with that of previous studies,especially the (..cap alpha..,/sup 6/He) results at high incident energy.Such comparisons show that configuration mixing is larger than predicted forthemore » higher-energy transitions in /sup 206/Pb. No significantconcentration of valence plus deep hole states could be found in/sup 206/Pb, whereas the previously known one valence plus one deepbump in /sup 114/Sn exhibits a maximum at /similar to/7.3 MeVhere mainly attributed to the(/ital g//sub 7/2/+g/sub 9/2/)/sub 8/sup +// state inagreement with the prediction of the quasiparticle phonon model.« less