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The University of Tennessee

Department of Physics and Astronomy

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Dr. Sean N. Liddick

Where to find me

220 Ayres Hall

1403 Circle Drive

(865) 974 7803 (UT)

 (865) 576 6076 (JIHIR)

liddicksn@ornl.gov

The valley of beta stability - more on the animation page

Research Activities

My research interests are the investigation of nuclear structure using decay spectroscopy techniques. In recent years these investigations have involved nuclei near double shell closures in the 100Sn ( N = Z = 50) and 78Ni (N = 50, Z = 28) regions. These experiments can be used to test theoretical nuclear structure models and provide input into models of stellar nucleosynthesis.

The recent experiments above 100Sn have all been focused on alpha decay measurements in this unique region. The experiments were performed at the HRIBF combining the capabilities of the RMS with our decay groups Double-sided Silicon Strip Detector (DSSD) used for correlating implanted ions with subsequent radioactive decays. The first experiment looked for (and found) an signature for super-allowed alpha decay in the decay of 105Te to 101Sn. Since the half-life of 105Te is too short for transmission through the RMS without unacceptable decay losses its alpha parent, 109Xe, was produced and implanted into the DSSD. The digital data acquisition which has been extensively developed by our group enabled the first detection of the 109Xe ->105Te->101Sn alpha decay chain.

The second experiment in this region found a small alpha decay branch from 109I. This put an end to a controversy over the previously reported, but never confirmed, proton decay from 105Sb. The experiment resulted in a new value for the proton separation energy in 105Sb. This value does not appear to affect the endpoint of the rp-process.

The next set of experiments focused on nuclei both above and below 78Ni. The first was performed at the HRIBF using the Moving Tape Collector (MTC) and four clover detectors for efficient detection of beta delayed gamma rays and focused on neutron rich isotopes of Cu and Ga and is currently under analysis by our collaborators at Mississippi State University. The other neutron-rich beta decay experiment was performed at the NSCL looking at the neutron-rich Co isotopes. This data set is currently undergoing analysis by Mustafa Rajabali, a graduate student in the group.

My thesis experiment was performed at the NSCL using the beta counting system for the correlation of implanted ions and their subsequent decays and the SeGA array for the detection of beta-delayed gamma rays. The experiment involved the investigation of neutron-rich Sc isotopes and provided evidence for the non-existence of a neutron shell closure in the Ti isotopes at N= 34, contrary to shell model calculations. The fate of the N = 34 shell closure now awaits an experiment probing the properties of 54Ca.

I have also developed a few animations to describe various concepts and/or techniques used in nuclear science. One animation can be used as an introduction to nuclear science by linking the periodic table with the chart of the nuclides. Another provides a visual description for the the valley of beta stability. There are also two animations on the hardware and techniques used in beta decay experiments. There is one desrcibing the correlation between an implantation event and a subsequent decay event in a DSSD and another one the charge collection inside a pixel of the DSSD.

Selected Recent Publications

Digital pulse processing in silicon detectors for the detection of fast alpha decays

Nuclear Instruments and Methods in Physics Research B, (in preparation).

S.N. Liddick, I. G. Darby, R. Grzywacz, C. Mazzocchi, K.P. Rykaczewski

  

Discovery of the 109Xe to 105Te to 101Sn alpha decay chain

AIP, Conference Proceedings, (in preparation)

S.N. Liddick, R. Grzywacz, C. Mazzocchi, R.D Page, K.P. Rykaczewski, J.C. Batchelder, C.R. Bingham,et al.

  

Rare isotope discoveries with digital electronics

Nuclear Instruments and Methods in Physics Research B, 261, 1103 (2007),

R. Grzywacz, C.J. Gross, A. Korgul, S.N. Liddick, C. Mazzocchi, R.D. Page, K.P. Rykaczewski

  

Discovery of 109Xe and 105Te: superallowed alpha decay near doubly magic 100Sn

Physical Review Letters, 98, 212501 (2007).

S.N. Liddick, R. Grzywacz, C. Mazzocchi, R.D Page, K.P. Rykaczewski, J.C. Batchelder, C.R. Bingham,et al.

  

Half-life and spin of 60Mn

Physical Review C, 73, 044322 (2006).

S.N. Liddick, P.F. Mantica, B.A. Brown, M.P. Carpenter, A.D. Davies, M. Horoi, R.V.F. Janssens,et al.

  

Beta decay of odd-A 57Ti and 59V

Physical Review C, 72, 054321 (2005).

S.N. Liddick, P.F. Mantica, R. Broda, B.A. Brown, M.P. Carpenter, A.D. Davies, B. Fornal,et al.

  

Beta decay studies of neutron-rich nuclei produced using projectile fragmentation at the NSCL

Nuclear Instruments and Methods in Physical research B, 241, 195 (2005).

P.F. Mantica, S.N. Liddick B.E. Tomlin,et al.

  

Development of shell closures at N = 32, 34; (I.) Beta decay of neutron-rich Sc isotopes

Physical Review C, 70, 064303 (2004).

S.N. Liddick, P.F. Mantica, R. Broda, B.A. Brown, M.P. Carpenter, A.D. Davies, B. Fornal,et al.

  

Lowest Excitations in 56Ti and the Predicted N = 34 Shell Closure

Physical Review Letters, 92, 072502 (2004).

S.N. Liddick, P.F. Mantica, R.V.F. Janssens, R. Broda, B.A. Brown, M.P. Carpenter, A.D. Davies, et al.

Invited Talks

Discovery of the 109Xe to 105Te to 101Sn alpha decay chain,

International Conference on Proton Emitting Nuclei and related areas, Lisbon, Portugal, June 2006

 

Discovery of the 109Xe to 105Te to 101Sn alpha decay chain,

Radioactive Nuclear Beams 7, Cortina d'Ampezzo, Italy, July 2006

 

Development of shell structure in the neutron-rich pf shell region,

Symposium of Exotic Nuclei and Nuclear Forces, Tokyo, Japan, March 2006

 

Tracking the Monopole Migration of the neutron f5-2 state near the N = 32 Subshell Closure,

Radioactive Nuclear Beams 6, Argonne, Illinois, Sept. 2002