Seminarium Fizyki Jądra Atomowego

One of the basic facts that we are taught about nuclear structure physics is that there are three main structural paradigms; nuclei with the ratio of energies E(4+)/E(2+) near 3.3 are deformed rotors, those with E(4+)/E(2+) ≈ 2 are spherical vibrators, and those with E(4+)/E(2+) ≈ 2.5 are γ-soft. These paradigms arose from the early solutions of the Bohr Hamiltonian, and are discussed at length in nearly all textbooks on nuclear physics. There is a further prevailing belief about structural evolution that as we move away from closed shells – where experimental data clearly indicate spherical-shaped ground states – and the number of valence particles increases, we first pass through a region of spherical vibrators, then into the domain of either γ-soft rotors or well-deformed rotational nuclei.
A region that is often used to demonstrate this kind of structural evolution, and indeed touted as some of the best examples of nearly harmonic vibrational motion, has been near the midneutron-shell nuclei around Z = 50. When examined individually, nuclei near Z = 50 do indeed look very vibrational; however, detailed systematics reveal consistent and serious deviations from expected bahaviour for harmonic vibrators, leading us to conclude that they are not. This raises the question if some of our best example of spherical vibrational nuclei are not vibrational, are there any examples of nuclei that do behave as such? This presentation will outline the properties that harmonic vibrational states should possess, and confront these expectations with experimental data including very recent results on the Cd isotopes.


Szanowni Państwo,

w związku z tym, że seminarium 2 maja 2019 r. nie odbędzie się ze względu na święta 1 i 3 maja br. serdecznie zapraszamy na seminarium do ŚLCJ UW, które odbędzie się 26 kwietnia 2019 r. (piątek) o godz. 11:00 w budynku ŚLCJ UW przy ul. Pasteura 5a, na którym:

dr Magda Zielińska (IRFU/DPhN, CEA, Universite Paris-Saclay, Gif-sur-Yvette, Francja)

wygłosi referat pt.:

„Coulomb-excitation experiments with the Q3D spectrometer at MLL”

Abstract: Coulomb excitation is a well-established method to investigate electromagnetic properties of low-lying excited states in atomic nuclei. The measured excitation cross sections can be directly related to E2 and E3 transition strengths, as well as to quadrupole moments of short-lived excited states, without any nuclear-model assumptions required. The first Coulomb-excitation experiments were performed in the 1950s, employing only particle spectroscopy. The advent of high-resolution gamma-ray spectroscopy in the 1970s enabled complex multi-step Coulomb-excitation studies of deformed nuclei, and the possibility to perform Coulomb-excitation experiments without gamma-ray detection has almost been forgotten. They still represent, however, an interesting alternative to the more popular gamma-particle coincidence measurements, especially for nuclei with low level density. In the seminar I will present very preliminary results of our recent experimental campaign with the Q3D magnetic spectrometer at Meier-Leibnitz Laboratory in Munich, with a focus on octupole collectivity in Zr isotopes and implications of the remeasurement of the B(E2; 2+1 -> 0+1) value in 104Pd for exotic-beam studies at ISOLDE.