6th Dec 2011 ISOLDE Workshop, CERN Reaction Dynamics studies with 6,7 Li and 9 Be nuclei at Pelletron, Mumbai, India Vivek Parkar University of Huelva, Spain Previous affiliation : Bhabha Atomic Research Centre, Mumbai, India

Outline of Talk:  Introduction to 14UD Pelletron facility, Mumbai, India  Studies with stable weakly bound ( 6,7 Li and 9 Be) nuclei:  Fusion cross-sections  Inclusive and exclusive breakup  Dipole Polarizabilities of 7 Li and 9 Be  Future prospects with light RIBs at ISOLDE

Started in 1988

A] Basic Research  Reaction studies near barrier  Fission studies  Nuclear Structure  Atomic Physics  Radio Chemistry studies  Magnetism B] Applied Research  Radiation damage studies  Radiation Biology  Accelerator Mass Spectroscopy (AMS)  Track etched membrane  Bio-environmental studies

Reactions with stable weakly bound nuclei Low breakup threshold Stable ions 6 Li   +d, S  d =1.48 MeV 7 Li   +t, S  t =2.47 MeV 9 Be   +  +n, S  n =1.57 MeV Advantage  large intensity and good beam quality  Study effect of breakup channel on elastic scattering and fusion cross-sections  Inclusive and exclusive breakup studies Next step: Reaction dynamics with light RIBs

Fusion cross-sections from online and offline  ray measurements 6,7 Li+ 144,152 Sm 6,7 Li+ 90 Zr 6,7 Li+ 198 Pt 6,7 Li+ 165 Ho 6,7 Li+ 159 Tb 9 Be+ 124 Sn 9 Be+ 89 Y Motivation : Fusion in presence of breakup channel  enhance fusion due to coupling OR suppress fusion due to loss of flux Online  ray technique: When ER is short lived (few secs)   ray de-excitation from the excited states of that ER Offline  ray technique: When ER is long lived (few mnts - days)  Measurement of  rays after beta decay/Electron capture  Fusion = Σ  ER

Evaporation Residue Measurement Off-beam intensities of charac- teristic  -lines from  decay of ER and half-life were measured F.C. Target & Catcher Beam

P. K. Rath et al., PRC 79, R (2009) (Rapid Communication)

Suppression (~28%) at E>Vb  breakup Enhancement at E<Vb  target deformation  Effect of breakup and deformation coexist Projectile breakup vs. target deformation P. K. Rath et al., Nucl Phys. A (Accepted)

V.V.Parkar et al., PRC 82, (2010) C. Palshetkar et al.,PRC 82, (2010)

Systematic of fusion suppression factor (i) For a particular projectile, the suppression factor is more or less independent of the product Z P Z T, (ii) suppression increases with decreasing breakup threshold of the projectile.

Exploring fusion at deep sub-barrier energies New sensitive off-beam method KX -  rays coincidence A. Lemasson et al., NIMA 598, 445 (2009) A. Shrivastava et al., PRL 103, (2009)

Inclusive and Exclusive breakup study 6 Li+ 65 Cu 6 Li+ 209 Bi 6,7 Li+ 90 Zr 9 Be+ 89 Y

Measurements: typical 2D spectra E (arb. unit)  E (arb. unit ) 7 Li 6 Li  t,d,p (a)(b) (c)(d)  Beam: 6 Li,  Energy: MeV  Target: 209 Bi ~330  g/cm 2 self-supporting  4 telescopes of SSB

Inclusive alpha production No evaporation alpha; E  evp <E  cent  incl  ~ direct reaction

Universal behaviour of inclusive alpha cross-sections

S. Santra et al., Phys. Rev. C (Submitted) Below barrier,   =  Reaction Otherwise,  CF +    Reaction Complete reaction picture for 6 Li+ 209 Bi

Exclusive breakup study of 6 Li FC 209 Bi (1 mg/cm 2 ) 6 Li Beam (~40nA) T 1  T 2 (d) T3()T3() T 4 (d) M1M1 M2M2 Detectors: 2 telescopes (  E: ~ 33  and E: ~ 500  ), 2 telescopes (  E:~150  and E: ~1000  ), and 2 single monitors (E ~ 2000  ) of Si surface barrier detectors Measured: Light charged particles in singles as well as coincidence, in list mode Angular range: 50 o -170 o. Energy: 36 and 40 MeV

Projectile breakup Direct breakup: Projectile breaks up directly into fragments at any excitation energy larger than breakup threshold. Sequential breakup: Projectile excited to resonant state followed by breakup, or it can exchange a few nucleon with the target and then breaks up. 6 Li 209 Bi  d 6 Li 6 Li* 5 Li 209 Bi   d p n

Typical two dimensional spectra with and without coincidence conditions. Counts Ch. No. 55 o 65 o

Inclusive and exclusive  -production  CDCC results with full coupling agrees with the average of two sets of experimental data for 3+ resonant state  Total   d (theory) <<    (incl)    p (exp) +   d (th) <<   (incl)  Other possible sources : (1) ( 6 Li, 4 He) (2) ( 6 Li, 5 He  n+ 4 He) (3) ( 6 Li, 7 Li  4 He+t) (4) partial fusion (d-cap) S. Santra et al., PLB 677, 139 (2009)

Dipole polarizability of 7 Li, 9 Be Elastic scattering

 Centre of matter distributions and centre of charge distributions of a nucleus do not coincide (e.g. deuteron, 7 Li, 6 He, 11 Li etc.) in the presence of strong electric field.  Transition between states of opposite parity. (For normal nuclei states of opposite parity are at high excitation energy)  For weakly bound nuclei  low breakup threshold, continuum states of opposite parity are nearby.  The effect is very small. (2% change in elastic cross section of d Pb (α d =0.70 fm 3 ), Similar effect expected for 7 Li Pb (α 7Li = fm 3 ). Introduction

 Beam :- 7 Li Target :- enriched 208 Pb (on Carbon backing) Beam energies :- E 7Li = MeV (All energies below Coulomb Barrier) Experimental Details T 4 : T 2 : T 1 : FC 208 Pb T 3 : Li Beam

Measured Spectra

CDCC Calculation Details  The diagonal and coupling potentials calculated using cluster folding method, R – 7 Li - target separation r - separation between clusters. Continue…… R r  t 208 Pb VV VtVt

 A value of DP found from a precise measurement of elastic scattering data to be,  = fm 3  Loosely bound unstable nuclei (e.g. 6 He, 11 Li, 11 Be) DP effect more important. V. V. Parkar et al., Phys. Rev. C (Rapid Com.), 78, R (2008) Polarizability parameter 

For 9 Be : S. K. Pandit et al., Phys. Rev. C (Rapid Com.), 84, R (2011)

Future prospective at ISOLDE  Reactions with 8,9,11 Li and 7,10,11,12,14 Be on similar targets to study complete reaction dynamics and compare with existing 6,7 Li and 9 Be data  Dipole polarizability studies for number of nuclei GLORIA UHU, Spain

Team Members S. Kailas, A. Chatterjee, S. Santra, A. Shrivastava, K. Mahata, K. Ramachandran, V. Jha, B. J. Roy, S. K. Pandit, P. K. Rath Nuclear Physics Division, BARC, Mumbai V. Nanal, R. G. Pillay, R. Palit DNAP, TIFR, Mumbai