Introduction Experimental result Discussion Conclusion Impact of the intruder orbitals on the structure of neutron-rich Ag isotopes KIM, Yung-Hee GANIL 9Be+238U fission experiment Introduction n-rich Ag isotopes : Triaxiality Two worlds in shell model Results Spectra & level scheme Signature splitting : Evidence of triaxiality Discussion Shell model calculation Conclusion I’d like to present result from prompt gamma-ray spectroscopy from fission fragment from 9Be+238U near the Coulomb barrier Investigating the Impact of the intruder orbitals on the structure of neutron-rich Ag isotopes

Introduction Experimental result Discussion Conclusion 238U(9Be,fγ) prompt γ-ray spectroscopy on isotopically identified fragments ΔZ/Z ∼ 1.5% ΔA/A ∼ 0.45% Ag A. Navin et al., Physics Letters B 728 (2014) 136–140 VAMOS++ 9Be (10μm) Unlike many of you who are studying fission process it self, we use fission as a tool to populate n-rich nuclei near Sn and to study the structure. In 2011 The fission of 238U on 9Be was carried out in GANIL 238U to 9Be has capable of populating n-rich nuclei over wide range of elements and it can excite to relatively high spin states. The fission was carried out inverse kinematics to get advantage from kinematical focusing The VAMOS++ large acceptance spectrometer coupled to EXOGAM Clover Ge-Detector array was used for prompt-g-ray spectroscopy. Due to large acceptance and isotopic identification of the VAMOS++ (click) Which has very good resolution accounting the energy is around the Coulomb barrier. we could get prompt g-ray spectroscopy without any unambiguity with good statistics in n-rich nuclei. From these advantages, this one experiment could produce results with various topic in nuclear structure. Doppler correction resolution 1.3MeV ~10keV in backward direction middle 15keV FWHM 238U(9Be,fγ) transfer/fusion-fission Various n-rich nuclei (rel.) High spin state VAMOS++ & EXOGAM Wide acceptance + isotopic ID In-beam γ-ray spectroscopy w/ good Doppler correction 238U (6.2 MeV/u) FF1 FF2 20° EXOGAM S. Pullanhiotan et al., Nucl. Instr. and Meth. A, 593,(2008) 343-352

238U(9Be,fγ) prompt γ-ray spectroscopy -Single particle motion Introduction Experimental result Discussion Conclusion 238U(9Be,fγ) prompt γ-ray spectroscopy -Single particle motion Single particle motion (Large-scale shell-model) 124-128Sb/122-126In: E2/M1 competition, natural seniority breaking 121-123Cd: shell model interaction 132Te: shell model interaction Collective motion (IBM/TPSM) 105,106Zr: Triaxiality/shape co-existence 114-119Rh: Triaxiality The various results can be cartegorized in two main topics, first is the subject more concerned about single particle motion near the shell closure. One good example is the Sb/In structure across the Sn shell closure. These nuclides were interpreted by large scale shell model calculations which is fully microscopic point of view. Collaboration EXOGAM+VAMOS / GAMMASPHERE 143-153Pr: Resolving structural uncertainty M. Rejmund et al., Phys. Lett. B 753 (2016) 86–90

238U(9Be,fγ) prompt γ-ray spectroscopy -Collective motion Introduction Experimental result Discussion Conclusion 238U(9Be,fγ) prompt γ-ray spectroscopy -Collective motion Single particle motion (Large-scale shell-model) 124-128Sb/122-126In: E2/M1 competition, natural seniority breaking 121-123Cd: shell model interaction 132Te: shell model interaction Collective motion (IBM/TPSM) 105,106Zr: Triaxiality/shape co-existence 114-119Rh: Triaxiality On the otherhand for nuclides in the midshell, the collective properties of nuclides were investigated. such as triaxiality of nuclides in the rotational band or shape co-exsistance. They are interpreted by more collective models such as TPSM or IBM calculations using deformed basis in the wave functions. Collaboration EXOGAM+VAMOS / GAMMASPHERE 143-153Pr: Resolving structural uncertainty A. Navin et al., Phys. Lett. B. in press (2016)

238U(9Be,fγ) prompt γ-ray spectroscopy Ag isotopes Introduction Experimental result Discussion Conclusion 238U(9Be,fγ) prompt γ-ray spectroscopy Ag isotopes Single particle motion (Large-scale shell-model) 124-128Sb/122-126In: E2/M1 competition, natural seniority breaking 121-123Cd: shell model interaction 132Te: shell model interaction Proton # Pr Te Sb Collective motion (IBM/TPSM) 105,106Zr: Triaxiality/shape co-existence 114-119Rh: Triaxiality Collective motion through microscopic view 113,118-121Ag Sn In In nuclear chart, you can see the result from this experiment with different topics What I’d like to show you is the combining these two topics for nuclei in between which is the neutron rich Ag isotope. Ag Rh Zr Neutron # Collaboration EXOGAM+VAMOS / GAMMASPHERE 143-153Pr: Resolving structural uncertainty http://www.nndc.bnl.gov

Expected triaxial deformation at 113-121Ag Introduction Experimental result Discussion Conclusion Expected triaxial deformation at 113-121Ag Ag = Distance from shell closure Y. X. Luo et al., J. Phys. G: Nucl. Part. Phys. 31 (2005) 1303–1327 For more Ag isotopes triaxiality is expected to continue from the systematics from lighter Ag and also from systematics from odd-Z isotopes Y-Nb-Rh where the triaxial deformation increase as Z moves closer to the Sn shell closure. Systematics Y-Nb-Rh  closer shell closures, stronger triaxial deformation Triaxiality near n-rich nuclei at lighter Ag isotopes A≤110 Observable: Direct: Doublet bands (Chiral, Wobbling) Indirect: Large signature splitting, Signature inversion

Expected triaxial deformation at 113-121Ag Introduction Experimental result Discussion Conclusion Expected triaxial deformation at 113-121Ag 108Ag 109Ag J. Sethi et al. Phys. Lett. B 725 (2013) 85–91 S. Roy et al. Phys. Lett. B 710 (2012) 587–593 The n-rich Ag isotopes the triaxial deformation can be expected For the Ag isotope below A 110 triaxial deformation was confirmed by the observable directly chiral dublet bands or indirectly by large signature splitting which is compared with deformed shell models. Systematics Y-Nb-Rh  closer shell closures, stronger triaxial deformation Triaxiality near n-rich nuclei at lighter Ag isotopes A≤110 Observable: Direct: Doublet bands (Chiral, Wobbling) Indirect: Large signature splitting, signature inversion

Two worlds in shell model Introduction Experimental result Discussion Conclusion Two worlds in shell model M. Rejmund et al., PRC 93, 024312 (2016) A. Navin et al., Physics Letters B 728 (2014) 136 As you may well know, the shell model interpretations are quite different between the different region. Where near the shell closure, the sphereical shell model with spereical basis are used, It is limited in this region due to the expontially increasing model space moving from the shell closure. But recently due to increaed computing power and development of calculation techniques it is expanding its calculable regions. On the otherhand for the midshell nuclides deformed shell models or Nilsson like models are used. Many models of this kind assumes deformed core or basis, with few quasi-particle outside of the core, From this it has significantly less computing power and give intuitive explanation of the collective motion of the nucleus. For the neutron rich Ag are now in the border between these two worlds and previously light Ag isotope near stability were explained by deformed shell models. But if it could be interpreted with spherical shell model would give different view view And it can make bridge between two worlds. From these motivations I would like to show the experimental results. Spherical shell model Spherical basis Nuclei near shell closure High computing power needed Increasing calculable regions Deformed shell model Deformed basis (assumption/exp. data deformation of core is needed) Mid-shell nuclei Less computing power n-rich Ag can be bridge between two worlds

Spectrum of 113,116-121Ag New spectra 113,118-121Ag Introduction Experimental result Discussion Conclusion Spectrum of 113,116-121Ag x3 x3 x3 This is the newly observed spectrum of odd-A Ag isotopes, these ones are singles spectrum and the insets are showing coincidence spectra The analysis was done until the coincidence spectrum could be observed As you can see the largest peaks connecting to each other shows similar energy This is the newly observed even-A Ag isotopes of 118 and 120 Ag isotopes, You can see there is doublet in the low E and high E peak with similar energy showing similar spectra. New spectra 113,118-121Ag Similar spectra from the light Ag

Smooth evolution of the Level scheme Introduction Experimental result Discussion Conclusion Smooth evolution of the Level scheme Odd-A Even-A v v v v M.-G. Porquet et al., Eur. Phys. J. A 18 (2003) 25–30 This is the level scheme of newly observed odd-A Ag isotopes, You can see the level have large energy straggling and it evolves smoothly for different isotopes In case of even-A Ag the levels are more equidistance different from odd-A Ag. And different isotopes show similar energy. This similar structure for different isotope doesn’t end only in this isotopes but they are quite consistent through out very long chain of isotopes. v v Smooth evolution of level energies Odd-A large energy staggering Even-A regular level spacing

Evidence of triaxiality in odd-A -Large signature splitting Introduction Experimental result Discussion Conclusion Evidence of triaxiality in odd-A -Large signature splitting This is the signature splitting of odd–A Ag which measures the energy straggling of different levels And the large signature splitting are one of the eveidence of the triaxiality. What is striking is the large and constant signature splitting over very long chain of isotopes Through out the N 50 to 82 magicity in low lying states. This is quite different from Rh or lighter isotopes where signature splitting shows evolution. LARGE & CONSTANT signature splitting

Evidence of triaxiality in odd-A -Large signature splitting Introduction Experimental result Discussion Conclusion Evidence of triaxiality in odd-A -Large signature splitting This is the signature splitting of odd–A Ag which measures the energy straggling of different levels And the large signature splitting are one of the eveidence of the triaxiality. What is striking is the large and constant signature splitting over very long chain of isotopes Through out the N 50 to 82 magicity in low lying states. This is quite different from Rh or lighter isotopes where signature splitting shows evolution. LARGE & CONSTANT signature splitting over long chain of isotopes 50<N<82

Evidence of triaxiality in even-A -Signature inversion Introduction Experimental result Discussion Conclusion Evidence of triaxiality in even-A -Signature inversion This constancy in signature spltting is also observed in even A Ag until mass 114 but in this case they show a inversed signature splitting where favored signature have larger S(J) different from odd-A case The singnature inversion it is also thought as a finger print of triaxiality although there debate going on why signature inversion arises. Constant signature inversion (N<69)

Evidence of triaxiality in even-A -Signature inversion Introduction Experimental result Discussion Conclusion Evidence of triaxiality in even-A -Signature inversion But when we move to N=69 the signauture inversion becomes smaller and it changes to normal signature when it goes to A=118, A=120 So from these systematics for long chain of isotopes the question arised that What is the origin of large and constant signature splitting of odd-A Ag isotopes And why in even-A isotopes signature evolved from signature inversion to normal signature splitting. So to understand this behavior, microscopic large scale shell model calculation were carried out. Constant signature inversion (N<69) Normal signature (N>69) N=69

Large-scale shell-model calculation Introduction Experimental result Discussion Conclusion Large-scale shell-model calculation v The calculation was carried out in the restricted space of jj45pna interaction shown here. This is because of the large space needed for the calculation and also it was not able to reproduce Their structure for the heavier Ag isotopes. The calcualtion result gives very good agreement with the experimental value reproduing its level order, energy. There is some shriked can be seen in the high spin states which is also seen in Cd calculation Probabliy due to small space we used. This calcualtion was also used for the Cd, In isotopes and showed good agreement with the experiment. Diagonal neutron-neutron interaction was adjusted 1p3/2 1f5/2 LSSM calculation in restricted space jj45pna interaction π(g9/2, p1/2), ν(d3/2, s1/2, h11/2) orbitals Good agreement with experiment (level ordering & energy reproduction)

Large-scale shell-model calculation Introduction Experimental result Discussion Conclusion Large-scale shell-model calculation Odd-A Even-A v This is showing all the calculation for this experiment. Which we can see good agreement between the experiment and the calculation . LSSM calculation in restricted space jj45pna interaction π(g9/2, p1/2), ν(d3/2, s1/2, h11/2) orbitals Good agreement with experiment (level ordering & energy reproduction)

Shell-model calculation result -signature splitting- Introduction Experimental result Discussion Conclusion Shell-model calculation result -signature splitting- 119-121Ag : Large signature splitting 116Ag : Signature inversion 118-120Ag : Normal signature All features are well reproduced! Odd-A The signature spltting wise the large signature splitting at low lying state is well reproduced. And evolution from signature inversed 116Ag to normal signature in 118, 120 Ag are also well reproduced. The wave function shows that πg9/2 νh11/2 intruder state scheme dominates, therefore to get more deeper insight, we carried out more simpler calculation including only two orbital Even-A Dominant contribution from πg9/2-3xνh11/2 m intruder orbital

Two-shell shell-model calculation Signature splitting Introduction Experimental result Discussion Conclusion Two-shell shell-model calculation Signature splitting Large Signature splitting Only πg9/2 νh11/2 space Odd-A : Large signature splitting Even-A : Signature inversion Normal signature Essential features are reproduced Odd-A Signature inversion favored The calculation only including the two shell shows quite good reproduction of level order and energy accounting its simplicity, And when we calculate signature splitting it reproduces the essential features of the experiment Where the large and relatively constant signature splitting in odd-A Ag as function of neutron occupancy in h11/2 shell And also evolution from signature inversion to normal signature in even-A Ag The h11/2 occupancy corresponds to exactly to the full calculation result where 116Ag is 3.5 and 118Ag is 5. And as the h11/2 occupancy is increased more than 7 the signature is almost constant This evolution corresponds to where particle-hole interaction changes to the hole-hole interaction. unfavored 116Ag Nh11/2=3.5 Even-A 118Ag Normal Signature Even-A Signature evolution : particle-hole (Nh11/2<6)  hole-hole (Nh11/2>6) 120Ag

Introduction Experimental result Discussion Conclusion New level scheme of 113,118-121Ag Striking evolution in signature splitting in 50<N<82 evidenced towards triaxialty Microscopic shell model reproduces structure without any assumption in deformation Essentially understood by simple intruder g9/2, h11/2 shell-model  Simplicity under complicated structure due to band from intruder orbital πg9/2-3xνh11/2m MORE features!! e.g. Inheritance from Cd in Ag isotope, natural seniority breaking Even-A Ag In conculsion The new level scheme of 113,121Ag was determined. The large consistancy in level energy and signature splitting could be obseved which is strikin. To understand the structure of this nuclei we carried out large scale shell model calculation Which reproduced the levels very well for the first time in this region. Although the structure looks quite complicated, The structures could be essentially understood with only two intruder orbital h11/2 g9/2 There are more features I could not present due to time limit but if you are interested please ask me LOL….

Merci  Thank you