Gamma-Ray Studies of a = 119-126 Tin Isomers Formed in Deep Inelastic Heavy Ion Collisions.

The purpose of the present study was to investigate the feasibility of using deep-inelastic heavy-ion collisions as spectroscopic tool to study yrast isomerism in A > 120 tin nuclei which cannot be produced in conventional fusion-evaporation reactions. Enriched 1mg/cm ^2 ^{122}Sn and ^{124}Sn targets, backed with lead, were placed at the center of the Argonne-Notre Dame gamma-ray Facility. In-beam and off-beam gamma-ray singles and gamma gamma coincidences were recorded following the collisions with pulsed ^{76 }Ge, ^{80}Se and ^{136}Xe beams at energies of {~}{15}% above the Coulomb barrier. Experimental results include the identification of new I^pi = 10^+ isomers in even-A ^{122 }Sn, ^{124}Sn, and ^ {126}Sn and first characterizations of isomeric I^pi = 27/2^- decays in odd-A ^{119}Sn, ^{121}Sn, and ^ {123}Sn nuclei. The obtained level schemes are discussed in terms of shell model configurations. For even-A tin isotopes, the 10^+ isomers are interpreted as (nu h _{11/2})^{n} seniority v = 2 states. The measurement of their isomeric half-lives completes a series of B(E2;10^+to8 ^+) determinations in ^ {116-130}Sn nuclei illustrating the predicted dependence of E2 transition rates between j^{n} states on h _{11/2} subshell occupation number. The results establish half-filling of the h_ {11/2} in tin isotopes to occur close to mass number A = 123. The 27/2^- isomers identified in odd-A tin nuclei are interpreted as (nu h_{11/2})^ {n} seniority v = 3 states. Observed level energies are found to be in excellent agreement with predictions from fractional parentage calculations. The gammagamma coincidence data have also provided yield distributions of even-even deep-inelastic reaction products in both projectile and target regions. General features of the observed yield patterns are discussed within the framework of N/Z equilibration of the dinuclear system. Such calculations can be used to predict the outcome of future experiments. The new method of populating high-spin states in neutron-rich isotopes may aid in experimentally accessing up to now unexplored regions of the nuclear chart.