ENTRY C2319 20180613 C177C231900000001 SUBENT C2319001 20180613 C177C231900100001 BIB 13 42 C231900100002 TITLE New Isotopes of Einsteinium C231900100003 AUTHOR (B.G.Harvey,A.Chetham-Strode Jr,A.Ghiorso, C231900100004 G.R.Choppin, S.G.Thompson) C231900100005 REFERENCE (J,PR,104,1315,1956) C231900100006 #doi:10.1103/PhysRev.104.1315 C231900100007 INSTITUTE (1USABRK,1USAUCX) C231900100008 FACILITY (CYCLO,1USABRK) The Crocker Laboratory 60-inch C231900100009 cyclotron. C231900100010 SAMPLE The amount of Bk249 available was only 1.2x10**-8 g, C231900100011 or about 3x10**13 atoms. The target material was C231900100012 deposited as a very thin layer over a rectangular C231900100013 area 0.6x6 mm on a 0.005-cm-thick gold foil. (This C231900100014 small target area was chosen to match the area of the C231900100015 most intense helium-ion beam.) C231900100016 DETECTOR (PROPC) A windowless proportional counter was assumed C231900100017 to give a counting efficiency of 90% for the C231900100018 beta-particles from Bk249 mounted on thick platinum C231900100019 plates. C231900100020 METHOD (REC,CHSEP,ACTIV) The beam passed first through the C231900100021 gold foil and then through the Bk249 target, so that C231900100022 nuclear reaction products were ejected from the C231900100023 target in the forward direction. They were caught on C231900100024 a 0.00025-cm thick gold "catcher" foil placed about C231900100025 5.5 mm from the target foil. By this method it was C231900100026 possible to bombard the Bk249 target a large number C231900100027 of times without the necessity of dissolving it. Some C231900100028 45 bombardments, many of them for as long as 9 hours, C231900100029 were made with no loss of target material. The Bk249 C231900100030 target also contained a known amount of Cm244 from C231900100031 which Cf246 was produced by the (alpha,2n) reaction. C231900100032 MONITOR (96-CM-244(A,2N)98-CF-246,,SIG) C231900100033 MONIT-REF (,A.Chetham-Strode,P,UCRL-(3322),1956) C231900100034 ERR-ANALYS (DATA-ERR) The accuracy of the cross-section C231900100035 measurements was limited to about 30% by (1) C231900100036 uncertainty in the amount of Bk249 in the target (the C231900100037 very soft beta- activity of Bk249 is not easy to C231900100038 count accurately, since the counting yield is very C231900100039 sensitive to the thickness of the sample), and (2) C231900100040 counting statistics in those experiments in which C231900100041 yields were measured by alpha-pulse analysis. C231900100042 DECAY-DATA (97-BK-249,280.0D,B-) C231900100043 HISTORY (20180613C) BP C231900100044 ENDBIB 42 0 C231900100045 COMMON 1 3 C231900100046 DATA-ERR C231900100047 PER-CENT C231900100048 30.0 C231900100049 ENDCOMMON 3 0 C231900100050 ENDSUBENT 49 0 C231900199999 SUBENT C2319002 20180613 C177C231900200001 BIB 4 8 C231900200002 REACTION (97-BK-249(A,N)99-ES-252,,SIG) C231900200003 DECAY-DATA (99-ES-252,140.0D,A,6640.0) C231900200004 COMMENT Compiler's comment: The half-life given for Es-252 is C231900200005 a factor 3 different from recent value. Authors C231900200006 mention that their value is only approximate and C231900200007 based only on alpha-pulse analysis, not taking into C231900200008 account the (at their time uncertain) decay by EC. C231900200009 STATUS (CURVE) Fig. 6, page 1318. C231900200010 ENDBIB 8 0 C231900200011 NOCOMMON 0 0 C231900200012 DATA 2 10 C231900200013 EN DATA C231900200014 MEV MB C231900200015 23.932 1.426E-01 C231900200016 26.606 5.720E-01 C231900200017 26.963 7.583E-01 C231900200018 28.270 7.906E-01 C231900200019 29.905 1.037E+00 C231900200020 30.767 9.442E-01 C231900200021 34.957 9.641E-01 C231900200022 35.908 5.660E-01 C231900200023 39.831 3.575E-01 C231900200024 40.247 3.969E-01 C231900200025 ENDDATA 12 0 C231900200026 ENDSUBENT 25 0 C231900299999 SUBENT C2319003 20180613 C177C231900300001 BIB 3 3 C231900300002 REACTION (97-BK-249(A,2N)99-ES-251,,SIG) C231900300003 DECAY-DATA (99-ES-251,1.5D,A,6480.0) C231900300004 STATUS (CURVE) Fig. 6, page 1318. C231900300005 ENDBIB 3 0 C231900300006 NOCOMMON 0 0 C231900300007 DATA 2 16 C231900300008 EN DATA C231900300009 MEV MB C231900300010 24.051 4.116E+00 C231900300011 26.517 1.312E+01 C231900300012 26.874 1.758E+01 C231900300013 28.211 2.258E+01 C231900300014 28.716 1.951E+01 C231900300015 29.935 1.776E+01 C231900300016 30.678 1.219E+01 C231900300017 31.747 1.285E+01 C231900300018 34.897 1.021E+01 C231900300019 35.938 1.087E+01 C231900300020 35.938 8.031E+00 C231900300021 36.740 7.865E+00 C231900300022 37.899 8.822E+00 C231900300023 39.920 8.373E+00 C231900300024 39.949 9.896E+00 C231900300025 40.187 7.622E+00 C231900300026 ENDDATA 18 0 C231900300027 ENDSUBENT 26 0 C231900399999 SUBENT C2319004 20180613 C177C231900400001 BIB 4 9 C231900400002 REACTION (97-BK-249(A,3N)99-ES-250,,SIG) C231900400003 COMMENT Compiler's comment: Authors suggest that Es250 also C231900400004 can be produced due to decay of Bk249 to Cf249, C231900400005 T1/2=280 days, modern values 330 days. Multiple C231900400006 reactions/decays on Cf249 could lead to Es250; C231900400007 however, half-life value of Bk249 makes these C231900400008 contributions small. C231900400009 DECAY-DATA (99-ES-250,8.HR,EC) C231900400010 STATUS (CURVE) Fig. 6, page 1318. C231900400011 ENDBIB 9 0 C231900400012 NOCOMMON 0 0 C231900400013 DATA 2 4 C231900400014 EN DATA C231900400015 MEV MB C231900400016 28.746 1.608E+00 C231900400017 31.718 2.826E+00 C231900400018 36.740 3.907E+00 C231900400019 39.860 5.457E+00 C231900400020 ENDDATA 6 0 C231900400021 ENDSUBENT 20 0 C231900499999 SUBENT C2319005 20180613 C177C231900500001 BIB 4 9 C231900500002 REACTION (97-BK-249(A,4N)99-ES-249,,SIG) C231900500003 COMMENT Compiler's comment: Authors suggest that Es250 also C231900500004 can be produced due to decay of Bk249 to Cf249, C231900500005 T1/2=280 days, modern values 330 days. Multiple C231900500006 reactions/decays on Cf249 could lead to Es250; C231900500007 however, half-life value of Bk249 makes these C231900500008 contributions small. C231900500009 DECAY-DATA (99-ES-249,2.0HR,A,6760.0) C231900500010 STATUS (CURVE) Fig. 6, page 1318. C231900500011 ENDBIB 9 0 C231900500012 NOCOMMON 0 0 C231900500013 DATA 2 6 C231900500014 EN DATA C231900500015 MEV MB C231900500016 34.273 8.776E-01 C231900500017 35.878 1.823E+00 C231900500018 36.710 2.683E+00 C231900500019 38.523 5.995E+00 C231900500020 39.831 3.411E+00 C231900500021 39.979 4.429E+00 C231900500022 ENDDATA 8 0 C231900500023 ENDSUBENT 22 0 C231900599999 ENDENTRY 5 0 C231999999999