Measurement of the E c:m: 184 keV Resonance Strength in the 26g Alp; 27 Si Reaction C. Ruiz, 1, * A. Parikh, 2,† J. Jose ´, 3,4 L. Buchmann, 1 J. A. Caggiano, 1 A. A. Chen, 5 J. A. Clark, 2 H. Crawford, 6 B. Davids, 1 J. M. D’Auria, 6 C. Davis, 1 C. Deibel, 2 L. Erikson, 7 L. Fogarty, 8 D. Frekers, 9 U. Greife, 7 A. Hussein, 10 D. A. Hutcheon, 1 M. Huyse, 11 C. Jewett, 7 A. M. Laird, 12 R. Lewis, 2 P. Mumby-Croft, 12 A. Olin, 1 D. F. Ottewell, 1 C. V. Ouellet, 5 P. Parker, 2 J. Pearson, 5 G. Ruprecht, 1 M. Trinczek, 1 C. Vockenhuber, 1 and C. Wrede 2 1 TRIUMF, Vancouver, BC V6T 2A3, Canada 2 Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124, USA 3 Departament de Fı ´sica i Enginyeria Nuclear, Universitat Polite ´cnica de Catalunya, Barcelona, Spain 4 Institut d’Estudis Espacials de Catalunya (IEEC), Barcelona, Spain 5 McMaster University, Hamilton, ON L8S 481, Canada 6 Simon Fraser University, Burnaby, BC V5A 1S6, Canada 7 Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA 8 National University of Ireland, Maynooth, Co. Kildare, Ireland 9 Institut fu ¨r Kernphysik, Westfa ¨lische Willhelms-Universita ¨t Mu ¨nster, 48149 Mu ¨nster, Germany 10 University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada 11 Katholieke Universiteit Leuven, 3000 Leuven, Belgium 12 Department of Physics, University of York, York YO10 5DD, United Kingdom (Received 13 April 2006; published 28 June 2006) The strength of the E c:m: 184 keV resonance in the 26g Alp; 27 Si reaction has been measured in inverse kinematics using the DRAGONrecoil separator at TRIUMF’s ISAC facility. We measure a value of ! 35 7 eV and a resonance energy of E c:m: 184 1 keV, consistent with p-wave proton capture into the 7652(3) keV state in 27 Si, and discuss the implications of these values for 26g Al nucleosynthesis in typical oxygen-neon white-dwarf novae. DOI: 10.1103/PhysRevLett.96.252501 PACS numbers: 24.30.v, 25.40.Lw, 26.50.+x, 27.30.+t Introduction.—The recent detection of decaying 26g Al [t 1=2 7:2 0:210 5 yr] via its characteristic 1.809 MeV ray by the RHESSI and INTEGRAL satellites has fur- thered our understanding of the production sites of this radioisotope [1,2]. The COMPTEL all-sky map of the 1.809 MeV line [3] points to young, high-mass progenitors such as core collapse supernovae (CCSN) and Wolf-Rayet stars [4]. Though previous studies suggested that all of the 26g Al in the Galaxy [presently measured as 2:8 0:8M [5] ] could have been entirely produced in CCSN [6], these new results have suggested that CCSN may be a much less dominant component, and that other sources must contrib- ute, thought chiefly to be Wolf-Rayet stars [7]. However, classical novae are one potential source of 26g Al and it has been shown that up to 0:4M of the Galactic abundance could have been produced in these sites [8]. Of particular importance to the calculation of nova-synthesized 26g Al abundances are the 25 Alp; 26 Si and 26g Alp; 27 Si reaction rates, the former being the most uncertain. The 26g Alp; 27 Si reaction rate at typical oxygen-neon white-dwarf nova (ONeWD) temperatures is dominated by a single resonance around E c:m: 188 keV [9,10]. An unpublished measurement of this resonance strength in normal kinematics yielded a value of 55 9 eV [9]. The final abundance of 26g Al synthesized in a typical ONeWD hydrodynamic calculation is somewhat sensitive to this strength. Because of the long lifetime of 26g Al, space-based -ray observatories such as INTEGRAL are unable to detect it from individual sources. Therefore, the likely primary progenitors can only be inferred from the Galactic 26g Al distribution. However, with a firm under- standing of the 26g Alp; 27 Si rate we can infer solid upper limits for the nova contribution to Galactic 26g Al as a secondary source. Experimental method. —This measurement was per- formed using the DRAGON recoil separator in the ISAC radioactive ion beam facility at TRIUMF. A high-power SiC target [11] was bombarded with up to 70 A of 500 MeV protons from TRIUMF’s sector focussing cyclo- tron, producing radioactive 26g Al which then diffused out of the target and into a rhenium surface-ionization tube. An enhancement to the surface ionization was provided using on-line laser ionization within the tube [12]. A 26 prod- ucts were separated using a high resolution mass separator. This beam was injected into a radio-frequency quadrupole accelerator (RFQ) for initial acceleration up to 0.15 A MeV and stripped to a higher charge state using a thin carbon foil before being injected into a continuously variable energy drift-tube linear accelerator (DTL) which allowed accel- eration between 0.15–1.8 A MeV [13]. The beam was delivered in bunches separated by 86 ns in time with a bunch width of less than two nanoseconds FWHM and an energy spread of typically 1% FWHM at 0.2 A MeV. PRL 96, 252501 (2006) PHYSICAL REVIEW LETTERS week ending 30 JUNE 2006 0031-9007= 06=96(25)=252501(4) 252501-1 2006 The American Physical Society