In-Beam Spectroscopy of the Extremely Neutron Deficient Nuclei 169Ir and 110Xe

This thesis describes new results obtained from experimental studies of the extremely neutron-deficient isotopes 169Ir and 110Xe, close to the proton drip-line. The experiments use state-of-the-art equipment for nuclear spectroscopy where a large high-resolution Germanium-detector array is coupled to a high-transmission recoil separator and using the highly selective recoil-decay tagging technique. The work is based on two experiments performed at the Accelerator Laboratory of the University of Jyväskylä, Finland. The experimental techniques used are described as are the experimental set-ups. Comparison between experimental results and theoretical predictions are made. The thesis also briefly summarises the theoretical models employed to interpret the experimental results. The results for 169Ir point to a rotational-like behaviour of a moderately deformed nucleus exhibiting triaxial shape. The experimental results do not fully agree with theoretical predictions for the shape evolution of the neutron-deficient iridium isotopes, approaching the proton drip-line. The results for 110Xe indicate an emergence of enhanced collectivity near the N=Z line in the region of the nuclear chart above 100Sn. These findings are interpreted as a possible effect of increased neutron-proton isoscalar pair correlations, a residual interaction effect not accounted for in present-day nuclear models.QC 2010111

In-Beam Spectroscopy of Extremely Neutron Deficient Nuclei 110Xe, 163Ta, 169Ir and 172Hg

This thesis describes new results obtained from experimental studies of the extremely neutron-deficient isotopes 110Xe, 163Ta, 169Ir, and 172Hg, close to the proton drip-line. The experiments used state-of-the-art equipment for nuclear spectroscopy where a large high resolution Germanium-detector array was coupled to a high-transmission recoil separator.The highly selective recoil-decay tagging technique was applied in order to identify andstudy the most weakly populated reaction channels. The work is based on four experimentsperformed at the Accelerator Laboratory of the University of Jyväskylä, Finland. The experimental techniques used and the experimental set-ups are described. Comparisonbetween experimental results and theoretical predictions are made. The thesis also brieflysummarises the theoretical models employed to interpret the experimental data. The results for 110Xe indicate an emergence of enhanced collectivity near the N=Z linein the region of the nuclear chart above 100Sn. These findings are interpreted as a possible effect of increased neutron-proton isoscalar pair correlations, a residual interaction effect not accounted for in present-day nuclear models. The findings for 163Ta reveal three strongly coupled band structures built on differentquasiparticle configurations. The low-lying yrast band exhibits strong signature splittingindicative of a significant triaxial shape asymmetry. An intriguing possibility exits forenhanced octupole correlation in 163Ta, where the odd-proton is proposed to couple to anoctupole-vibrational phonon. However, further investigations are needed to elucidate thisscenario. Also for 169Ir do the properties of the yrast structure point to a rotational-like behaviourof a moderately deformed nucleus exhibiting a triaxial shape. For neither 163Taor 169Ir do the experimental results fully agree with theoretical predictions for the shapeevolution of the neutron-deficient tantalum and iridium isotopes, approaching the protondrip-line.The nearly constant level spacing in 172Hg between the lowest excited 2+, 4+ and 6+states suggests a transition to a near-spherical harmonic collective vibrational structureas compared with heavier even-even Hg isotopes around the neutron midshell and above.The experimental data have been compared with total Routhian surface calculations and quasiparticle random phase approximation calculations.QC 2010080

In-Beam Spectroscopy of the Extremely Neutron Deficient Nuclei 169Ir and 110Xe

This thesis describes new results obtained from experimental studies of the extremely neutron-deficient isotopes 169Ir and 110Xe, close to the proton drip-line. The experiments use state-of-the-art equipment for nuclear spectroscopy where a large high-resolution Germanium-detector array is coupled to a high-transmission recoil separator and using the highly selective recoil-decay tagging technique. The work is based on two experiments performed at the Accelerator Laboratory of the University of Jyväskylä, Finland. The experimental techniques used are described as are the experimental set-ups. Comparison between experimental results and theoretical predictions are made. The thesis also briefly summarises the theoretical models employed to interpret the experimental results. The results for 169Ir point to a rotational-like behaviour of a moderately deformed nucleus exhibiting triaxial shape. The experimental results do not fully agree with theoretical predictions for the shape evolution of the neutron-deficient iridium isotopes, approaching the proton drip-line. The results for 110Xe indicate an emergence of enhanced collectivity near the N=Z line in the region of the nuclear chart above 100Sn. These findings are interpreted as a possible effect of increased neutron-proton isoscalar pair correlations, a residual interaction effect not accounted for in present-day nuclear models.QC 2010111

In-Beam spectroscopy of extremely neutron deficient nuclei [sup 110]Xe [sup 163]Ta [sup 169]Ir and [sup 172]Hg

This thesis describes new results obtained from experimental studies of the extremely neutron-deficient isotopes 110Xe, 163Ta, 169Ir, and 172Hg, close to the proton drip-line. The experiments used state-of-the-art equipment for nuclear spectroscopy where a large highresolution Germanium-detector array was coupled to a high-transmission recoil separator. The highly selective recoil-decay tagging technique was applied in order to identify and study the most weakly populated reaction channels. The work is based on four experiments performed at the Accelerator Laboratory of the University of Jyväskylä, Finland. The experimental techniques used and the experimental set-ups are described. Comparison between experimental results and theoretical predictions are made. The thesis also briefly summarises the theoretical models employed to interpret the experimental data. The results for 110Xe indicate an emergence of enhanced collectivity near the N=Z line in the region of the nuclear chart above 100Sn. These findings are interpreted as a possible effect of increased neutron-proton isoscalar pair correlations, a residual interaction effect not accounted for in present-day nuclear models. The findings for 163Ta reveal three strongly coupled band structures built on different quasiparticle configurations. The low-lying yrast band exhibits strong signature splitting indicative of a significant triaxial shape asymmetry. An intriguing possibility exits for enhanced octupole correlation in 163Ta, where the odd-proton is proposed to couple to an octupole-vibrational phonon. However, further investigations are needed to elucidate this scenario. Also for 169Ir do the properties of the yrast structure point to a rotational-like behaviour of a moderately deformed nucleus exhibiting a triaxial shape. For neither 163Ta or 169Ir do the experimental results fully agree with theoretical predictions for the shape evolution of the neutron-deficient tantalum and iridium isotopes, approaching the proton drip-line. The nearly constant level spacing in 172Hg between the lowest excited 2+, 4+ and 6+ states suggests a transition to a near-spherical harmonic collective vibrational structure as compared with heavier even-even Hg isotopes around the neutron midshell and above. The experimental data have been compared with total Routhian surface calculations and quasiparticle random phase approximation calculations

A Geant4 simulation package for the SAGE spectrometer

A comprehensive Geant4 simulation was built for the sage spectrometer. The simulation package includes the silicon and germanium detectors, the mechanical structure and the electromagnetic fields present in sage. This simulation can be used for making predictions through simulating experiments and for comparing simulated and experimental data to better understand the underlying physics.peerReviewe

Determination of absolute internal conversion coefficients using the SAGE spectrometer

A non-reference based method to determine internal conversion coefficients using the SAGE spectrometer is carried out for transitions in the nuclei of 154Sm, 152Sm and 166Yb. The Normalised-Peak-to-Gamma method is in general an efficient tool to extract internal conversion coefficients. However, in many cases the required well-known reference transitions are not available. The data analysis steps required to determine absolute internal conversion coefficients with the SAGE spectrometer are presented. In addition, several background suppression methods are introduced and an example of how ancillary detectors can be used to select specific reaction products is given. The results obtained for ground-state band E2 transitions show that the absolute internal conversion coefficients can be extracted using the methods described with a reasonable accuracy. In some cases of less intense transitions only an upper limit for the internal conversion coefficient could be given.peerReviewe

Production and investigation of neutron-rich isotopes with and around N=126 using gas flow transport method

Neutron-rich isotopes of heavy nuclei are until now poorly studied. In this work we investigate neutron-rich osmium isotopes produced in multi-nucleon transfer reactions. The reaction 136Xe+208Pb at energy near Coulomb barrier is used for production of osmium isotopes. The CORSAR-V setup is used to record the characteristics of osmium isotopes. The separation of the reaction products is based on their respective volatility. Experimental results are presented and discussed.peerReviewe

Prompt and delayed spectroscopy of 199At

The neutron-deficient nucleus At199 has been studied through γ-ray and electron spectroscopy, using the recoil-decay tagging technique. Two experiments were conducted, using a gas-filled recoil separator with a focal-plane spectrometer alone and together with a germanium-detector array at the target position. The resulting level scheme for At199 includes a new isomer with a half-life of 0.80(5) μs and a spin and parity of (29/2+). The 13/2+ isomer, which de-excites via an M2 transition to the 9/2− ground state, was measured to have a half-life of 70(20) ns. Our earlier version of the level scheme for At197 has been updated as well.peerReviewe

Experimental study of 1/2(+) isomers in At-199,At-201

Using fusion-evaporation reactions, a gas-filled recoil separator, and recoil-electron and recoil-electron-α tagging techniques, a new isomeric 1 2 + state [T1/2 = 45(3) ms] in 201At is identified, and an earlier reported corresponding state [T1/2 = 273(9) ms] in 199At is confirmed. The 1 2 + state is suggested to originate from an intruder π(s1/2) −1 configuration. In addition, nuclear structure of states below and above this 1 2 + state are studied in both nuclei. The isomer decays through a cascade of an E3 transition followed by a mixed M1/E2 transition to the 9 2 − ground state, and it is interpreted to be fed from nearly spherical 3 2 + and 5 2 + states originating from π(d3/2) −1 and π(d5/2) −1 configurations, respectively.peerReviewe

Confirmation of the new isotope 178Pb

The extremely neutron-deficient isotope 178Pb has been produced. The GREAT spectrometer at the focal plane position of the gas-filled separator RITU was used to study the α decay of 178Pb and its α-decay chain through α-α correlations. The α decay was measured to have an energy and half-life of Eα= 7610(30) keV and t1/2 = 0.21+0.21 −0.08 ms, respectively. The half-life is consistent with recent theoretical calculations using the Coulomb and proximity potential model. The α-decay reduced width and hindrance factor for 178Pb were deduced and correspond to an unhindered l = 0 transition. In addition, the mass excess of 178Pb and the α-decay Q value were calculated from the experimental results and compared to theoretical values.peerReviewe