Gamma-ray Spectroscopy: Into the 21st Century

6. Principles and Advantages of g-ray Tracking Efficiency � Proper summing of scattered gamma rays, no solid angle lost to suppressors Peak-to-background � Reject Compton events Doppler correction - Position of 1st interaction Polarization � Angular distribution of the 1st scattering Counting rate - Many segments

7. GRETINA Status

8. GRETINA Status

9. The First 4-crystal Detector Maximum mechanical deviation is 0.073 mm < 0.200 mm (meets spec) Signal rise time <80 nsec (meets spec) Integral crosstalk <0.2% (meets spec) Differential crosstalk <0.4% (meets spec) Energy resolution of two crystals meets specs- 2.3 keV at 1332 keV Manufacturer visiting in May

10. From GRETINA to GRETA

12. Structure Near the Driplines: Knockout Reactions

23. Shell Structure and Collective Modes Near The N=20 Shell Gap

26. 28Ne Gamma Spectra This is the singles Doppler-corrected gamma-ray spectrum of 28Ne produced by one-proton knockout from 29Na with a cross section of 1.45 mb. The v/c is 0.42. We had enough data for gamma-gamma coincidences and we see three in coincidence, at 1310, 1712, ad 893 keV (their relative intensities are 100, 24, and 15%). Only 1310 appears in the ENSDF database, and no spin and parity is assigned to the first level. It has been found in fragmentation and coulex, and based on intensity considerations assigned 21+ ? 01+. 1712 is reported in fragmentation. 893 only found recently in fragmentation (Belleguic 2005) but postulated to feed 21+ from 02+ in parallel with 1712 which also feeds 21+. This was shown as an evidence for low-lying 02+ and therefore shrink N=20 gap. Our high-statistics data proves that this is not the decay from the 02+, and so in principle there is no evidence for shrinked N=20 gap at 28Ne. In addition to these three lines, we have a fourth one, very strong and not in coincidence with anything else. Because of its intensity we postulate it is the 22+ to 02+. This is the singles Doppler-corrected gamma-ray spectrum of 28Ne produced by one-proton knockout from 29Na with a cross section of 1.45 mb. The v/c is 0.42. We had enough data for gamma-gamma coincidences and we see three in coincidence, at 1310, 1712, ad 893 keV (their relative intensities are 100, 24, and 15%). Only 1310 appears in the ENSDF database, and no spin and parity is assigned to the first level. It has been found in fragmentation and coulex, and based on intensity considerations assigned 21+ ? 01+. 1712 is reported in fragmentation. 893 only found recently in fragmentation (Belleguic 2005) but postulated to feed 21+ from 02+ in parallel with 1712 which also feeds 21+. This was shown as an evidence for low-lying 02+ and therefore shrink N=20 gap. Our high-statistics data proves that this is not the decay from the 02+, and so in principle there is no evidence for shrinked N=20 gap at 28Ne. In addition to these three lines, we have a fourth one, very strong and not in coincidence with anything else. Because of its intensity we postulate it is the 22+ to 02+.

33. 18N Results

34. n-p interaction

35. The Curious Case of 16C Anomalous hindered B(E2, 2+ ? 0+) of 0.26 W.u. in 16C ? low proton deformation. (N. Imai et al., PRL. 92 (2004) 062501) Inelastic scattering ? large neutron deformation. (Z. Elekes et al., PLB 586 (2004) 34) 18O systematic: first excited 2+ state at 2 MeV has T1/2 = 1.94 ps. A lifetime of similar order expected for the 2+ state at 1766 keV in 16C. Expect B(E2, 2+ ? 0+) of ~ 7 W.u. for 16C.