CERN Accelerating science

Article
Report number	CERN-EP-98-002
Title	Quadrupole-deformed and octupole collective bands in $^{228}$Ra
Author(s)	Gulda, K ; Mach, H ; Aas, A J ; García-Borge, M J ; Burke, D G ; Fogelberg, B ; Gietz, H ; Grant, I S ; Hagebø, E ; Hill, P ; Hoff, P ; Kaffrell, N ; Kurcewicz, W ; Lindroth, A ; Løvhøiden, G ; Martínez, T ; Mattsson, S ; Naumann, R A ; Nybø, K ; Nyman, G H ; Rubio, B ; Sánchez-Vega, M ; Taín, J L ; Taylor, R B E ; Tengblad, O ; Thorsteinsen, T F
Affiliation	(Univ. Warsaw) ; (Univ. Uppsala) ; (Univ. Oslo) ; (Insto. Estructura de la Materia, CSIC Madrid) ; (McMaster Univ. Hamilton) ; (Univ. Mainz) ; (The Schuster Laboratory, Manchester Univ.) ; (Univ. of Oslo) ; (Insto. Fisica Corpuscular, CSIC-Univ. Valencia, Burjassot) ; (Chalmers Univ. of Technol. Göteborg) ; (Dartmouth College, Hanover, NH 03755, USA) ; (CERN) ; (Univ. Bergen)
Publication	1998
Imprint	14 Jan 1998
Number of pages	18
In:	Nucl. Phys. A 636 (1998) 28-46
DOI	10.1016/S0375-9474(98)00191-2
Subject category	Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN ISOLDE ; IS322
Abstract	Spins and parities for collective states in $^{228}$Ra have been determined from conversion electron measurements with a mini-orange $\beta$-spectrometer. The fast-timing $\beta\gamma\gamma(t)$ method has been used to measure lifetimes of T$_{1/2}$=550(20) ps and 181(3) ps for the $2^{+}_{1}$ and $4^{+}_{1}$ members of the K=0$^{+}$ band, and T$_{1/2} \leqslant$ 7 ps and $\leqslant$ 6 ps for the $1^{-}_{1}$ and $3^{-}_1$ members of the K = $0^{-}$ band, respectively The quadrupole moments, $Q_{0}$ deduced from the B (E2; 2$_{1}^{+} \rightarrow 0_{1}^{+}$) and B (E2; 4$_{1}^{+} \rightarrow 2_1^{+}$) rates are in good agreement with the previously measured value and the systematics of the region. However, the B(E1) rates of $\geqslant$ 4 × 10$^{−4}$ e$^{2}$fm$^{2}$, which represent the first B(E1) measurements for this nucleus, are at least 25 times larger than the value previously suggested for $^{228}$Ra. The new results are consistent with the B(E1) rates recently measured for the neighbouring $^{227}$Ra and reveal octupole correlations in $^{228}$Ra.

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