ENTRY M0480 20130624 M067M048000000001 SUBENT M0480001 20130624 M067M048000100001 BIB 16 49 M048000100002 TITLE Isospin effects on the N-15(g,2n) reaction cross M048000100003 section. M048000100004 AUTHOR (K.G.McNeill,A.D.Bates,R.P.Rassool,E.A.Milne, M048000100005 M.N.Thompson) M048000100006 REFERENCE (J,PR/C,37,1403,1988) M048000100007 #doi:10.1103/PhysRevC.37.1403 M048000100008 INSTITUTE (3AULAML) M048000100009 FACILITY (BETAT,3AULAML) M048000100010 INC-SOURCE (BRST) M048000100011 METHOD (ACTIV) Measuring the yield of 0.511 mev gamma-quanta M048000100012 emitted following annihilation of positrons from the M048000100013 induced 9.97 min positron activity of N-13. M048000100014 DETECTOR (NAICR) M048000100015 SAMPLE Three samples, each weighing 24.9 g, were in the form M048000100016 of discs of diameter 31.85 mm and thickness 18.66 M048000100017 mm. They were formed under pressure from M048000100018 ammonium-sulfate powder ((N(H-4)-2)S(o-4)) which was M048000100019 enriched to 98% in N-15. M048000100020 PART-DET (AR) Annihilation radiation of positrons from the M048000100021 activity of N-13. M048000100022 ANALYSIS (UNFLD,PLA) The yield at a given energy is determined M048000100023 by the number of 0.511 MeV gamma rays detected at M048000100024 that energy. Yield points were measured at 200 keV M048000100025 intervals from 21 to 28 MeV. A total of three M048000100026 separate measurements was made over this whole M048000100027 range. These three runs were averaged. this averaged M048000100028 curve was then analyzed using the variable bin M048000100029 Penfold-Leiss method. M048000100030 ERR-ANALYS (DATA-ERR) Root-mean-squared errors. M048000100031 (ERR-1) The systematic errors are only estimated to be M048000100032 about 10%. M048000100033 COMMENT The cross section for the N-15(g,2n) reaction has M048000100034 been studied from 20 to 28 MeV. The cross section M048000100035 remains near zero for 3 MeV above threshold, then M048000100036 rises sharply at about 24 MeV, to a maximum value of M048000100037 1.7 mb. The shape is explained in terms of the M048000100038 density of states with isospin T> in N-14 at the M048000100039 relevant excitation energy. It must be noted that M048000100040 the present measurement determines only the cross M048000100041 section for transitions leading to the ground state M048000100042 of final nucleus N-13, i.e. the cross section of the M048000100043 reaction N-15(g,nn-0)N-13-g. All excited states of M048000100044 N-13 (the first is at 2.365 MeV) are proton M048000100045 unstable. M048000100046 EN-SEC (E-LVL,7-N-13) M048000100047 STATUS (CURVE) M048000100048 HISTORY (19910218C) M048000100049 (20130624A) Corrected by V.Varlamov: ERR-ANALYS, M048000100050 REACTION, STATUS. M048000100051 ENDBIB 49 0 M048000100052 COMMON 2 3 M048000100053 E-LVL ERR-1 M048000100054 MEV PER-CENT M048000100055 0.0 10. M048000100056 ENDCOMMON 3 0 M048000100057 ENDSUBENT 56 0 M048000199999 SUBENT M0480002 20130624 M067M048000200001 BIB 3 3 M048000200002 REACTION (7-N-15(G,2N)7-N-13,PAR,SIG,,BRS) M048000200003 DECAY-DATA (7-N-13,9.97MIN) M048000200004 HISTORY (20130624A) Corrected by V.Varlamov: BRA -> BRS. M048000200005 ENDBIB 3 0 M048000200006 NOCOMMON 0 0 M048000200007 DATA 3 30 M048000200008 EN DATA DATA-ERR M048000200009 MEV MB MB M048000200010 21. 0.0 .05 M048000200011 21.2 .02 .02 M048000200012 21.4 .03 .02 M048000200013 21.6 .11 .11 M048000200014 21.8 .11 .2 M048000200015 22. .12 .2 M048000200016 22.1 .09 .12 M048000200017 22.3 .22 .14 M048000200018 22.5 .31 .09 M048000200019 22.75 .21 .1 M048000200020 22.9 .33 .15 M048000200021 23.1 .21 .21 M048000200022 23.3 .19 .17 M048000200023 23.5 .19 .15 M048000200024 23.7 .42 .11 M048000200025 23.9 .16 .2 M048000200026 24.1 .22 .11 M048000200027 24.3 .39 .13 M048000200028 24.5 .41 .2 M048000200029 24.7 .62 .33 M048000200030 24.9 .88 .14 M048000200031 25.1 1.01 .11 M048000200032 25.3 1.2 .2 M048000200033 25.5 1.59 .23 M048000200034 25.7 1.65 .18 M048000200035 25.9 1.69 .13 M048000200036 26.1 1.7 .28 M048000200037 26.3 1.69 .45 M048000200038 26.5 1.54 .28 M048000200039 26.7 1.41 .14 M048000200040 ENDDATA 32 0 M048000200041 ENDSUBENT 40 0 M048000299999 ENDENTRY 2 0 M048099999999