Eur. Phys. J. A (2011) 47: 6
https://doi.org/10.1140/epja/i2011-11006-7

Letter

Blocking of coupling to the 0₂ ⁺ excitation in ¹⁵⁴Gd by the [505]11/2^- neutron in ¹⁵⁵Gd

¹ University of Western Cape, Department of Physics, P/B X17, ZA-7535, Bellville, South Africa
² University of Zululand, Department of Physics, P/B X1001, ZA-3886, Kwa Dlangezwa, South Africa
³ iThemba Laboratory for Accelerator Based Sciences, PO Box 722, ZA-7129, Somerset-West, South Africa
⁴ Faculty of Physics, St. Kliment Ohridski University of Sofia, 1164, Sofia, Bulgaria
⁵ University of Stellenbosch, Department of Physics, P/B X1, ZA-7602, Stellenbosch, South Africa
⁶ ATOMKI, POB 51, 4001, Debrecen, Hungary

Received: 30 July 2010
Revised: 15 November 2010
Accepted: 2 December 2010
Published online: 6 January 2011

Abstract

The concept that the first excited 0⁺ states in N = 90 nuclei are not a -vibration but a second vacuum formed by the combination of the quadrupole pairing force and the low density of oblate orbitals near the Fermi surface is supported by the blocking of this collective mode in ¹⁵⁴Gd from coupling to the [505]11/2^- single-particle quasi-neutron orbital in ¹⁵⁵Gd . The coupling of this orbital to the 2⁺ -vibration in ¹⁵⁴Gd is observed since this coupling is not Pauli-blocked.