Fragmentation of gold projectiles: From evaporation to total disassembly

We have studied the fragmentation of Au projectiles interacting with targets of C, Al and Cu at an incident energy ofE/A=600 MeV. The employed inverse kinematics allowed a nearly complete detection of projectile fragments with chargeZ≧2. The recorded fragmentation events were sorted according to three observables, the multiplicityM _lp of light charged particles, the largest atomic numberZ _max within an event, and a new observable,Z _bound, representing the sum of the atomic numbersZ of all fragments withZ≧2. Using these observables, the impact parameter dependence of the fragmentation process was investigated. For all three targets, a maximum mean multiplicity of 3 to 4 intermediate mass fragments (IMFs) is observed. The corresponding impact parameters range from central collisions for theC target to increasingly peripheral collisions for the heavier targets. It is found that the correlation between the IMF multiplicity andZ _bound, extending from evaporation type processes (largeZ _bound) to the total disassembly of the projectile (smallZ _bound), is independent of the target nucleus. This universal behaviour may suggest an — at least partial — equilibration of the projectile fragment prior to its decay.     

Resonance states of hydrogen nuclei 4H and 5H obtained in transfer reactions with exotic beams

To investigate ⁵H resonance states with a better instrumental resolution, we utilized the two-neutron transfer reaction ³H(t, p)⁵H accomplished with the use of a cryogenic liquid-tritium target and 57.5-MeV triton beam. As a result of this study, a valuable fraction of protons detected at ? _lab=18°–32° in ptn coincidence events was attributed to the states of the ⁵H nucleus. Two resonance states situated at 1.8±0.1 and 2.7±0.1 MeV above the t + n + n decay threshold were obtained in the missing mass energy spectrum of the ⁵H nucleus. The peak located close to E5_H was clearly seen in the ⁵H spectrum obtained from the energy distributions of ³H nuclei emitted in the reaction ²H(⁶He, ⁵H)³He at ? _lab=17°–32°. The width (Γ_obs≤0.5 MeV) obtained for the two ⁵H resonance states is surprisingly small. A state of ⁴H with E _res=3.3 MeV and γ ²=2.3 MeV was obtained in the reaction ²H(t, p)⁴H from the spectra of protons leaving the target at ? _lab=18°–32° and detected in coincidence with neutrons emitted in the decay of ⁴H nuclei.     

Correlations of neutral and charged particles in 40Ar- 58Ni reaction at 77 MeV/u

The measurement of the two-particle correlation function for different particle species allows to obtain information about the development of the particle emission process: the space-time properties of emitting sources and the emission time sequence of different particles. The single-particle characteristics and two-particle correlation functions for neutral and charged particles registered in forward direction are used to determine that the heavy fragments (deuterons and tritons) are emitted in the first stage of the reaction (pre-equilibrium source) while the majority of neutrons and protons originates from the long-lived quasi-projectile. The emission time sequence of protons, neutrons and deuterons has been obtained from the analysis of non-identical particle correlation functions.     

Quest for the 10He nucleus

The spectrum of ¹⁰He was studied by means of the ³H(⁸He, p)¹⁰He reaction at a laboratory energy of 25 MeV/A and small center-of-mass angles. Missing mass spectrum of ¹⁰He was derived from the obtained p-⁸He coincidence. A resolution of 0.7 MeV was achieved in this spectrum for the measured ¹⁰He energy. Most likely, a well isolated group of 10 events detected between 2 and 5 MeV and showing a maximum at about 3 MeV in the spectrum of the present work exhibits the ¹⁰He g.s. resonance.     

Data on light-fragment correlations in 40 Ar + 58 Ni at 77 MeV/nucleon

Results of the experimental study of p ⁴ He, d ³ He, dT, pT, p ³ He and, for the first time, nT, n ³ He, n ⁴ He correlations in the region of small relative momenta are presented. The data analysis provides an estimate of the effective source size or emission time.Received: 26 May 2003, Published online: 2 December 2003PACS: 25.70.Pq Multifragment emission and correlations     

Structure of 12Be: intruder d-wave strength at N=8

The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the [FORMULA: SEE TEXT]orbital and the [FORMULA: SEE TEXT], intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be.     

Study of complete and incomplete fusion for loosely bound projectiles 6He and 6Li on 165Ho and 166Er targets

Complete fusion (CF) and incomplete fusion (ICF) reactions were studied for the cases of the loosely bound ⁶He and ⁶Li projectiles bombarding ¹⁶⁶Er and ¹⁶⁵Ho targets at energy of about 10 MeV/nucleon. Experiments were carried out to test an approach exploiting the measured intensities of ?? rays emitted at the transitions between the yrast-band levels of reaction products formed after the termination of neutron evaporation. Partial waves feeding the CF reactions ¹⁶⁵Ho (⁶Li, ⁵ n) ¹⁶⁶Yb and ¹⁶⁶Er(⁶He, ⁶ n) ¹⁶⁶Yb as well as ICF ¹⁶⁵Ho (⁶Li, ??3n) ¹⁶⁴Er and ¹⁶⁶Er(⁶He, ??4n) ¹⁶⁴Er reaction channels were revealed from the obtained ??-ray data. The method of exit channel identification via the triple coincidence (??1-??2-light charged particle) was employed for these reactions study.