Thomas Glasmacher - Intermediate-Energy Coulomb Excitation

Intermediate-Energy Coulomb Excitation

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	The farther a nucleus is away from the valley of beta-stability, the less is generally known about it. Measurements become difficult because it is not easy to produce large amounts of these rare isotopes. They decay within milliseconds. We developed the experimental technique of intermediate-energy Coulomb excitation to study rare isotopes in flight and to measure basic nuclear structure observables before the atoms decay. This technique works with with beam rates of as low as a few particles per second. It is ideally suited to the exotic beams produced at the NSCL's Coupled Cyclotron Facility. We can measure the location of the first excited states in rare isotopes, as well as how strongly these states are coupled to the ground states. Geometrically this measurement is related to the shape of the nucleus, quantum-mechanically we measure the electric quadrupole transition matrix element between the two states.

Principle	The picture on the right shows a very simplified schematic setup of our experiment. The exotic beam enters from the left, gets excited in the Coulomb field of a heavy gold target and emits a gamma-ray. These gamma-rays are Doppler-shifted, since the beam moves with 30% of the speed of light. We need to measure the energy and the interaction point of the gamma-rays emitted to reconstruct the proper energy in the frame of the moving projectile. To do this, we need a position-sensitive gamma-ray detector.

Result	The spectrum for ⁴⁰S demonstrates the power of the experimental technique. In the laboratory we measure the spectrum shown in the top panel. A transition from the stationary gold target is visible as a peak, however the transition corresponding to the fast moving (v=0.27c) projectile is a broad bump. Only when the spectrum is transformed into the moving projectile frame (lower panel) does the transition corresponding to the ⁴⁰S beam become sharp. The gamma-ray in ⁴⁰S was observed for the first time in Heiko Scheit's thesis experiment.	Energy spectrum of ⁴⁰S observed in Heiko Scheit's thesis experiment.

Publications	Measurement of E2 transition strengths in ^32,24Mg. J.A. Church, C.M. Campbell, D.-C. Dinca, J. Enders, A. Gade, T. Glasmacher, Z. Hu, R.V.F. Janssens, W.F. Mueller, H. Olliver, B.C. Perry, L.A. Riley, and K.L. Yurkewicz. Phys. Rev. C 72 (2005) 054320. Quadrupole deformation of the self-conjugate nucleus ⁷²Kr. A. Gade, D. Bazin, A. Becerril, C.M. Campbell, J.M. Cook, D.-C. Dinca, T. Glasmacher, G.W. Hitt, M.E. Howard, W.F. Mueller, H. Olliver, J.R. Terry, and K. Yoneda. Phys. Rev. Lett. 95 (2005) 022502. Reduced transition probabilities to the first 2⁺ state in ^52,54,56Ti and development of shell closures at N=32,34. D.-C. Dinca, R. V. F. Janssens, A. Gade, D. Bazin, R. Broda, B. A. Brown, C. M. Campbell, M. P. Carpenter, P. Chowdhury, J. M. Cook, A. N. Deacon, B. Fornal, S. J. Freeman, T. Glasmacher, M. Honma, F. G. Kondev, J.-L. Lecouey, S. N. Liddick, P. F. Mantica, W. F. Mueller, H. Olliver, T. Otsuka, J. R. Terry, B. A. Tomlin, and K. Yoneda. Phys. Rev. C 71 (2005) 041302(R). E2 excitation strength in ⁵⁵Ni: Coupling of the ⁵⁶Ni 2₁⁺ collective core vibration to the f_7/2 odd neutron hole. K. L. Yurkewicz, D. Bazin, B. A. Brown, C. M. Campbell, J. A. Church, D.-C. Dinca, A. Gade, T. Glasmacher, M. Honma, T. Mizusaki, W. F. Mueller, H. Olliver, T. Otsuka, L. A. Riley, and J. R. Terry. Phys. Rev. C 70 (2004) 064321. Nuclear Structure in the vicinity of N=Z=28 ⁵⁶Ni. K.L. Yurkewicz, D. Bazin, B.A. Brown, C.M. Campbell, J.A. Church, D.-C. Dinca, A. Gade, T. Glasmacher, M. Honma, T. Mizusaki, W.F. Mueller, H. Olliver, T. Otsuka, L.A. Riley, J.R. Terry. Phys. Rev. C 70 (2004) 054319. Intermediate-energy Coulomb excitation of ⁵²Fe. K.L. Yurkewicz, D. Bazin, B.A. Brown, C.M. Campbell, J.A. Church, D.-C. Dinca, A. Gade, T. Glasmacher, M. Honma, T. Mizusaki, W.F. Mueller, H. Olliver, T. Otsuka, L.A. Riley, J.R. Terry. Phys. Rev. C 70 (2004) 034301. Detailed experimental study on intermediate-energy Coulomb excitation of ⁴⁶Ar. A. Gade, D. Bazin, C. M. Campbell, J. A. Church, D. C. Dinca, J. Enders, T. Glasmacher, Z. Hu, K. W. Kemper, W. F. Mueller, H. Olliver, B. C. Perry, L. A. Riley, B. T. Roeder, B. M. Sherrill, and J. R. Terry, Phys. Rev. C 68 (2003) 014302. Transition to the “Island of inversion”: Fast-beam g-ray spectroscopy of ^28,30Na, B.V. Pritychenko, T. Glasmacher, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, L.A. Riley, H. Scheit, Phys. Rev. C 66 (2002) 024325. Structure of the “island of inversion” nucleus ³³Mg. B.V. Pritychenko, T. Glasmacher, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, L.A. Riley, A. Sakharuk, H. Scheit, M. Steiner, and V. Zelevinsky, Phys. Rev. C 65 (2002) 061304(R). Transition to the “Island of inversion”: Fast-beam g-ray spectroscopy of ^28,30Na, B.V. Pritychenko, T. Glasmacher, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, L.A. Riley, H. Scheit, Phys. Rev. C 66 (2002) 024325. 0+g.s.→2⁺₁ excitations in the mirror nuclei ³²Ar and ³²Si. P.D. Cottle, Z. Hu, B.V. Pritychenko, M. Chromik, J.A. Church, M. Fauerbach, T. Glasmacher, R.W. Ibbotson, K.W. Kemper, L.A. Riley, H. Scheit, M. Steiner, Phys. Rev. Lett. 88 (2002) 172502. Structure of the “island of inversion” nucleus ³³Mg. B.V. Pritychenko, T. Glasmacher, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, L.A. Riley, A. Sakharuk, H. Scheit, M. Steiner, and V. Zelevinsky, Phys. Rev. C 65 (2002) 061304(R). B(E2;0⁺→2⁺) in ²⁶Si and mirror symmetry in the A=26 system. P.D. Cottle, B.V. Pritychenko, J.A. Church, M. Fauerbach, T. Glasmacher, R.W. Ibbotson, K.W. Kemper, H. Scheit, M. Steiner, Phys. Rev. C 64 (2001) 057304. Intermediate-energy Coulomb excitation. T. Glasmacher, Nucl. Phys. A 693 (2001) 90. Shape coexistence on the boundary of the “island of inversion”: Exotic beam spectroscopy of ³⁴Al, B.V. Pritychenko, T. Glasmacher, B.A. Brown, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, H. Scheit, Phys. Rev. C 63 (2001) 047308. First observation of an excited state in the neutron-rich nucleus ³¹Na, B.V. Pritychenko, T. Glasmacher, B.A. Brown, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, L.A. Riley, H. Scheit, Phys. Rev. C 63 (2001) 011305(R). Single particle structure along the boundary of the “island of inversion'”: Radioactive beam spectroscopy of ³³Si and ³⁴P. B.V. Pritychenko, T. Glasmacher, B.A. Brown, P.D. Cottle, R.W. Ibbotson, K.W. Kemper, H. Scheit, Phys. Rev. C 62 (2000) 051601(R). B(E2:0→2) in ¹⁸Ne and isospin purity in A = 18 nuclei. L. A. Riley, P. D. Cottle, M. Fauerbach, T. Glasmacher, K. W. Kemper, B. V. Pritychenko, H. Scheit. Phys. Rev. C 62 (2000) 034306. Spectroscopy of the 2⁺₁ state in ²²O and shell structure near the neutron dripline. P.G. Thirolf, B.V. Pritychenko, B.A. Brown, M. Chromik, T. Glasmacher, G. Hackman, R.W. Ibbotson, K.W. Kemper, T. Otsuka, L.A. Riley, H. Scheit, Phys. Lett. B 485 (2000) 16. Intermediate-energy Coulomb excitation of ¹⁹Ne. G. Hackman, Sam M. Austin, T. Glasmacher, T. Aumann, B. A. Brown, R. W. Ibbotson, K. Miller, B. Pritychenko, L. A. Riley, B. Roeder, and E. Spears, Phys. Rev. C 61 (2000) 052801(R). Role of intruder configurations in ^26,28Ne and ^30,32Mg, B.V. Pritychenko, T. Glasmacher, P.D. Cottle, M. Fauerbach, R.W. Ibbotson, K.W. Kemper, V. Maddalena, A. Navin, R. Ronningen, A. Sakharuk, H. Scheit, and V.G. Zelevinsky, Phys. Lett. B 461 (1999), 322. The 0⁺_g.s. → 2⁺₁ transition in ³⁸Ca and isospin symmetry in A=38 nuclei, P.D. Cottle, M. Fauerbach, T. Glasmacher, R.W. Ibbotson, K.W. Kemper, B. Pritychenko, H. Scheit, and M. Steiner, Phys. Rev. C 60 (1999), in print. A position sensitive high-efficiency NaI(Tl) photon-detection system for use with intermediate energy radioactive ion beams, H. Scheit, T. Glasmacher, R. W. Ibbotson, and P. G. Thirolf, Nucl. Instr. Meth. A 422 (1999), 124. Coulomb excitation of odd-A neutron-rich π(s-d) and ν(f-p) shell nuclei, R. W. Ibbotson, T. Glasmacher, P.F. Mantica, and H. Scheit, Phys. Rev. C 59 (1999) 642. Coulomb excitation at intermediate energies, T. Glasmacher, Ann. Rev. Nucl. Part. Sci. 48 (1998), 1. Quadrupole collectivity in ^32,34,36,38Si and the N=20 shell closure, R.W. Ibbotson, T. Glasmacher, B.A. Brown, L. Chen, M.J. Chromik, P.D. Cottle, M. Fauerbach, K.W. Kemper, D.J. Morrissey, H. Scheit, and M. Thoennessen, Phys. Rev. Lett. 80 (1998), 2081. Coulomb excitation of the one-neutron halo nucleus ¹¹Be. M. Fauerbach, M.J. Chromik, T. Glasmacher, P.G. Hansen, R.W. Ibbotson, D. Morrissey, H. Scheit, P. Thirolf, and M. Thoennessen, Phys. Rev. C 56 (1997), R1. Excitation and decay of the first excited state of ¹⁷Ne, M.J. Chromik, B.A. Brown, M. Fauerbach, T. Glasmacher, R. Ibbotson, H. Scheit, M. Thoennessen, and P.G. Thirolf, Phys. Rev. C 55 (1997), 1676. Collectivity in ⁴⁴S, T. Glasmacher, B.A. Brown, M.J. Chromik, P.D. Cottle, M. Fauerbach, R.W. Ibbotson, K.W. Kemper, D.J. Morrissey, H. Scheit, D.W. Sklenicka, and M. Steiner, Phys. Lett. B 395 (1997), 163. New region of strong deformation: the neutron-rich sulfur isotopes, H. Scheit, T. Glasmacher, B.A. Brown, J. Brown, P.D. Cottle, P.G. Hansen, R. Harkewicz, M. Hellstrm, R. Ibbotson, J.K. Jewell, K.W. Kemper, D.J. Morrissey, M. Steiner, P. Thirolf and M. Thoennessen, Phys. Rev. Lett. 77 (1996), 3967.

Thomas Glasmacher Professor of Physics and Associate Director (NSCL) Exp. Nuclear Physics
Updated 26 December 2005