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Relative energies of the πh112 and πs12 β-decay isomers of 147Tb82 and 151Ho84
V01ume 191, num6er 3
RELA71VE E N E R 6 1 E 5 0 F 7 H E 0 F 1477682AND 151H084
PHY51C5 LE77ER5 8
nh11/2 AND
11 June 1987
n51/2 p-DECAY 1 5 0 M E R 5
C.F. L1AN6, P. PAR15 Centre de 5pectr0metr1e Nuc1ea1re et de 5pectr0metr1e de Ma55e, F-91406 0r5ay, France
P. KLE1NHE1N2, 8. RU810, M. P11PAR1NEN 1 1n5t1tut)~r Kernphy51k, KFA Jf111ch, D-5170 J1111ch,Fed. Rep. 6ermany
D. 5CHARD7, A. P L 0 C H 0 C K 1 and R. 8ARDEN 651Darm5tadt, D-6100 Darm5tadt, Fed. Rep. 6ermany Rece1ved 11 Fe6ruary 1987
A1pha-9ammac01nc1denemea5urement5e5ta6115hthe re1at1veener91e50fthe 13-decay150mer51nJ4776 (E~(1.8 m1n)= 50.6(9) kev) and ~JH0 (E~(47 5) =41.4(9) kev) and u = 1.2+ f0r the t51H0 47 5150mer.
1n the 5pher1ca1 nuc1e1 ar0und N = 82 the pr0t0n5 a60ve 2 = 64 f111the 5t/2, h11/2, and d3/2 5he115. Fr0m recent 5y5temat1c 5tud1e5 [ 1 ] 0f the 0dd-2 N = 82 150t0ne5 1t 15 kn0wn that there the 5~/2 0r61ta1 15 the 10we5t-1y1n9 p051t1ve-par1ty 51n91e part1c1e 5tate, and the 5ame 15 e5ta6115hed [2,3] f0r the 0dd-A 76 nuc1e1 w1th 84 and 86 neutr0n5. 0 n e theref0re w0u1d expect that at 1ea5t tw0 13-decay1n9 150mer5 0ccur 1n the 5pher1ca1 0dd-2 nuc1e1 ar0und N = 8 2 w1th 65 and m0re pr0t0n5, and a num6er 0f 5uch examp1e5 are kn0wn. 1n m05t ca5e5 the h19h- and 10w-5p1n 150mer5 can 6e f1rm1y d15t1n9u15hed fr0m the pr0duct10n meth0d and fr0m the1r decay pr0pert1e5, 6ut 51nce they cann0t c0nnect thr0u9h •/-tran51t10n5 1t 15 4u1te d1ff1cu1t t0 determ1ne the1r re1at1ve exc1tat10n ener91e5. 70 kn0w the5e re1at1ve 150mer ener91e515 0fpart1cu1ar 1ntere5t 1n the N = 82 150t0ne5 51nce 5uch data are 0f v1ta1 1mp0rtance t0 determ1ne the pr0t0n 51n91e part1c1e 5pectrum a60ve 2 = 64. A5 Q~-mea5urement5 are 0ften n0t 5uff1c1ent1y accurate, and 5h0rt ha1f 11ve5 0f ne19h60ur1n9 even-2 150t0ne5 exc1ude tran5fer react10n 5tud1e5 1t 15 n0t kn0wn w1th certa1nty f0r any 0dd N---82 nuc1eu5 whether the hj ~/2 Permanent addre55: Department 0f Phy51c5, un1ver51ty 0f Jyv~15ky1~1,5F-40720 Jyv~15ky1~1,F1n1and.
0r the 51/2 51n91e pr0t0n f0rm5 the nuc1ear 9r0und 5tate. 7he N = 82 [3-decay 150mer5 are a150 p0pu1ated 1n a-decay, and 11/2- 15 f1rm1y e5ta6115hed f0r the N = 8 4 a-parent h19h-5p1n act1v1t1e5 fr0m the c0mpet1n9 6 7 [~+ decay 6ranch. A1th0u9h the 5p1n5 0f the 10w-5p1n N = 84 150mer5 are n0t mea5ured 1t 15 a1m05t certa1n that the 10w-5p1n a-decay5 c0nnect t0 the 10w-5p1n 150mer5 1n the N = 82 dau9hter. Accurate Q,-va1ue5 are thu5 kn0wn f0r 60th the h19h- and the 10w-5p1n 150mer5, 6ut a150 the5e data cann0t 5pec1fy the 150mer ener91e5 w1th1n 0ne nuc1eu5. 1n the pre5ent 5tudy 0f 15~H0 a-decay we have n0w mea5ured the re1at1ve 150mer ener91e5 6y 065erv1n9 •/-ray5 1n c01nc1dence w1th weak a-tran51t10n5 t0 exc1ted 5tate5 1n the dau9hter nuc1eu5. 0n1y 1n a few ca5e5 5uch a tran51t10n5 have 6een 065erved 1n rareearth nuc1e1, 6ut n0t 1n c01nc1dence w1th •/-ray5.0ur data 91ve the 150mer1c ener91e5 1n the 0ne-pr0t0n nuc1eu5 1477682 a5 we11 a5 1n the 151H084 parent nuc1eu5 w1th the accuracy 1nherent t0 •/-ray and apart1c1e ener9y determ1nat10n5. 1n add1t10n, the re5u1t5 5tr0n91y 5u99e5t a 1/2 + a5519nment f0r the ~5tH0 10w-5p1n [3-decay 150mer. 7he ~5~H0 act1v1t1e5 were pr0duced 1n the 10n 245
V01ume 191, num6er 3
PHY51C5 LE77ER5 8
~-Decay 0 f
151H0 • 151mH0
11 June 1987
N116 151H°
--~14776
ct-5pectrum
c.4
ct- Pr0jec t10n
×e•.4
0
~"
1
~
1 1200
10~,
-0 0 -0 -4-
200
1600
,
h 2
1 , 3 a - E n e r 9 y (HeV)
1 111
111
11
1111 1
1f1 1
1 1
1111
6ate c~ 2,260
111
LL•11
1
1~ 1111J..
600
1 ~
300
y-Pr0ject10n 0
0 151 75
0
~
0 151Dy
,~
0
00
~
0
0
~
0
1 0
1 200
1 /*00
a-part1c1e 51n91e5 5pectrum 0f f19. 2 wa5 06ta1ned w1th 600 MeV p•5 0n 7 a at 150LDE. 1n the ~5~H0 a-part1c1e 5pectra we c1ear1y 065erve tw0 weak tran51t10n5 w1th E ~ = 4260 a n d 4220 keV 1n add1t10n t0 the k n 0 w n [4] 4606 a n d 4517 keV 11ne5. F r 0 m the c01nc1dence data 1t 15 c1ear that the 1nten5e tran51t10n5 c0nnect the 150mer5, a n d that 60th 5ate111te 11ne5 feed the 354 keV 5/2 + exc1ted 5tate 1n 14776 (f19. 3). F r 0 m 1t5 ener9y, the 4260 keV 11ne c1ear1y 6e10n95 t0 the ~5~H0 10w-5p1n 150mer, and the
~L~ 600
Channe[ Num6er
151 ,, 67 910 8/+
F19. 1. •4776 y-ray5 065erved 1n c01nc1dencew1th the weak cttran51t10n5at 4220 and 4260 keV. 50urce 0f the 0r5ay 150CELE 11 0n-11ne ma55 5eparat0r thr0u9h the (3He, 11 n ) react10n w1th a 1.1 pA 6eam 0 f 2 8 0 MeV 3He 0n a me1ted • 10 9 7 6 tar9et. 7 h e 5eparated A = 151 act1v1ty wa5 c011ected f0r 40 5 0n tape a n d after tran5p0rt mea5ured f0r an e4ua1 per10d w1th a •/-ray 6 e ( L 1 ) a n d a 51 5urface-6arr1er a-part1c1e detect0r 1n c105e 180 ° 9e0metry. Re5u1t5 0f a~/-c01nc1dence mea5urement5 are 5h0wn 1n f19. 1. A n 1ndependent c01nc1dence exper1ment at the 6 5 1 0n-11ne ma55 5eparat0r u51n9 the 96M0(58N1, 3p) pr0duct10n react10n c0nf1rmed the5e f1nd1n95. 7 h e 246
11~111~ 5
F19.2. A1phapart1c1e51n91e5-5pectrum0f ma55 5eparated A= 151 act1v1t1e5 pr0duced w1th 600 MeV p•5 0n 7a mea5ured f0r 60 5 after 1 5 c011ect10nt1me. U a5519nment5are 1nd1cated f0r the tran51t10n5fr0m c5]H0(47 5, 1/2 + ) and ~5~H0(365, 11/2- ). 7he 0.5% 10w-ener9y5h0u1der1nthe 11ne5hape15an e1ectr0n1cart1fact.
C0
.
,
0
6ate c~ t~220
0
1 1+
~ .4
102
t, 11111 11 11
~
100
1 E~ 1
11111
~
1
1 1300
N~ ~
0
3~
7w=365 0
7/2"
72/
3/2 , ~ . ~ p 1.6h
~0~0/ ~.~ .... • 13*
1/*7 71~
651u82
F19. 3. 150mer1cexc1tat10nener91e51nJ4776and 15~H0fr0m J51H0 a-decay. Re1at1vect-tran51t10n1nten51t1e5are 91ven1nparenthe5e5.
11 June 1987
PHY51C5 LE77ER5 8
V01ume 191, num6er 3
4220 keV 11ne mu5t 6e attr16uted t0 15tH0 11/2decay and theref0re can 6e u5ed t0 determ1ne the re1at1ve 150mer ener91e5. 7 h e a6501ute ener91e5 0f the three 1nten5e 11ne51n f19. 2 are kn0wn [ 4 ] t0 + 3 keV, 6ut 1n the pre5ent c0ntext we 0n1y need t0 kn0w the re1at1ve ener91e5 0f the 1nten5e and the 5ate111te tran51t10n5, where the 5eparat10n 6etween the 4606 annd 4260 keV 11ne5 fr0m ~-ray data 15 kn0wn t0 +0.2 keV accuracy. W1th the re5u1t E~(11/2-, 11/2)-E~,(11/2-+5/2)=295.5(9) keV we 9et the exc1tat10n ener91e5 Ex(1 1/2-, 14776) = 5 0 . 6 ( 9 ) keV, and Ex, (1/2 +, 151H0)=41.4(9) keV, where the uncerta1nty 5tem5 ma1n1y fr0m the 11m1ted accuracy 0f the 5ate111te peak p051t10n5. 0 u r va1ue f0r the 11/2- ener9y 1n 14776 15 at var1ance w1th a h19h-re501ut10n ~-ray 5tudy [ 5] wh1ch p1aced the 1/2 + 150mer 50 keV a60ve the 1 1/2- 150mer. 7 h e 0n1y 0ther d1rect determ1nat10n 0f the exc1tat10n ener9y 15 a ( 14N, 118e) tran5fer react10n 5tudy wh1ch 9ave [6,7] Ex(11/2) = 110(30) 0r 80(30) keV. Va1ue5 der1ved fr0m mea5ured Q~-d1fference5 5t111 have rather 1ar9e uncerta1nt1e5; a recent mea5urement [8,9] 9ave Ex(11/2) = 130(90) keV. A5 a c0n5e4uence, the 1983 ad0pted va1ue [ 10] 0f 120(30) keV 15 a150 c1ear1y t00 1ar9e. We here c0u1d ment10n that 80(50) keV wa5 5u99e5ted [ 11 ] fr0m exper1menta1 ener91e5 0f pr0t0n part1c1e-h01e 5tate5 1n 1466d and 148Dy. We n0te that the 1nver510n 0f the 150mer5 6etween 14776 and 151H0 15 51m11ar a5 1n the ne19h60Ur1n9 153H0-14976 a-deCay pa1r. 7he 5ame C0nC1U510n Wa5 a1ready made 1n the 0r191na1 5tUdy [ 12] 0f 151H0 a-
decay, 6Ut 1t Wa5 6a5ed 0n the 1nC0rreCt ear1y 5/2 + a5519nment f0r the 10W-5p1n 150mer5. 709ether W1th the re5U1t5 1n ta61e 1 We a150 91Ve 1nten51ty 11m1t5 f0r add1t10na1 Un065erved a-tran51t10n5 t0 10w-1y1n9 14776 5tate5. 7 h e 1a5t c01umn c0nta1n5 1nten51ty rat105 fr0m 6arr1er penetrat10n ca1cu1at10n5 w1th the re5pect1ve/-va1ue5, 6ut 1t 15 c1ear that 5uch ca1cu1at10n5 91ve upper 11m1t5 f0r the 1~ 0 11ne5 51nce a chan9e 0f the 51n91e part1c1e c0nf19urat10n w111 cau5e add1t10na1 retardat10n. Fr0m the5e num6er5 0ne w0u1d expect a rather 1nten5e 1/2 + --,3/2 + 5ate111te 11ne. 7 h a t we d0 n0t 065erve 1t can 6e under5t00d 51nce the d3/2 5he1115 0n1y part1a11y f111ed 1n the 15~H0 parent nuc1eu5, wherea5 the d5/2 5he11 15 fu11y 0ccup1ed and theref0re the k1nemat1ca11y weaker tran51t10n 15 065erved. A5 wa5 ment10ned a60ve, the 5p1n va1ue 0f the ~5tH0 10w-5p1n 150mer 15 5t111 unc1ear, and a pr10r1 1/2 + 0r 3/2 + 5h0u1d 6e c0n51dered. 7 h e 3/2 + a1ternat1ve 15 c1ear1y 1nc0mpat161e w1th the 065erved a1nten51t1e5, 51nce 1n th15 ca5e the 1=0 tran51t10n t0 the 253 keV 3/2 + exc1ted 5tate 1n 14776 5h0u1d have at 1ea5t 13% 0f the 9r0und 5tate tran51t10n 1nten51ty wh1ch 15 c1ear1y ru1ed 0ut 6y exper1ment. Ana1090u5 c0n51derat10n5 a150 exc1ude the 0r191na1 5/2 + a5519nment f0r 10w-5p1n 151H0. 1n c0nc1u510n we have determ1ned fr0m u7-c01nc1dence mea5urement5 w1th h19h accuracy the re1at1ve ener91e5 0f the n5~/2 and rtht 1/2 13-decaY 150mer5 1n the 0ne-pr0t0n nuc1eu5 14776. 0Ur re5u1t5 501ve 1nc0n515tenc1e5 0f ear11er determ1nat10n5 wh1ch emp10yed d1fferent techn14ue5 that have much 1ar9er
7a61e 1 A1pha-tran51t10n51ndecay 0fN= 84 J5~H0(475, 1/2 +) and ~5~H0(365, 11/2 ) t010w-1y1n9J47761eve15. E~ (keV)
Re1at1ve 1nten51ty
4604 a) (4558) 6) (4359) 6) 4260 c~
100 < 1.1 <0.05 0.26(2)
4517 a) (4565) 6~ (4318) 6~ 4220 c)
100 <0.7 <0.01 0.036(4)
1:-,1r
E~
1
7,,,re~c~"c
1/2 +-, 1/2+ 1/2+-011/2 1/2+~ 3/2 + 1/2+--* 5/2 +
0 51 253 354
0 5 2 2
100 2.2 2.3 0.62
11/2---+11/211/2-~ 1/2 + 11/2---* 3/2 + 11/2--, 5/2 +
51 0 253 354
0 5 5 3
100 4.4 0.19 0.37
a>Fr0m ref. [ 4]. 6) 7ran51t10n n0t 065erved. c) Uncerta1nty f0r ener9y d1fferencet0 1= 0 tran51t10n 150.6 keV. •247
V01ume 191, num6er 3
PHY51C5 LE77ER5 8
uncerta1nt1e5. 7 h e pre5ent d a t a 91ve a150 a prec15e exc1tat10n ener9y f0r the ~51H0 10w-5p1n 150mer a n d d e t e r m 1 n e 1t5 5p1n a5 1/2 + . We t h a n k 0 . K1epper a n d R. K1rchner f0r the1r he1p dur1n9 the exper1ment5 at 6 5 1 , a n d 6 . Wa1ter, A. H u c k , C. R1chard-5erre a n d the ma55 5eparat0r 5taff f0r va1ua61e 5upp0rt dur1n9 a te5t-6eam t1me at 1 5 0 L D E / C E R N . We ackn0w1ed9e e1uc1dat1n9 d15cu5510n5 w1th J. 810m4v15t a n d 0 . 5chu1t.
Reference5 [1] P. K1e1nhe1n2, 8. Ru610, M. 09awa, M. P11par1nen, A. P10ch0ck1, D. 5chardt, R. 8arden, 0. K1epper, R. K1rchner and E. R0eck1, 2. Phy5. A 323 (1985)705. [2] J.A. 521Jc2, M.W. J0hn5 and 8.51n9h, Nuc1. Data 5heet5 46 (1985) 1. [3] P. Kemn1t2, L. Funke, F. 5tary, E. W111, 6. W1nter, 5. E1f5tr6m, 5.A. Hj0rth, A. J0hn50n and 7h. L1nd61ad, Nuc1. Phy5. A 311 (1978) 11.
248
11 June 1987
[4] A. Ryt2, At. Data Nuc1. Data 7a61e5 23 (1979) 507. [ 5] 6.D. A1kha20v, K.A. Me211ev, Yu.N. N0v1k0v, N. 6an6aatar, K.Ya. 6r0m0v, V.6. Ka11nn1k0v, A. P0tempa, E. 51en1aw5k1 and F. 7arkany1, 2. Phy5. A 310 (1983) 247. [6] M. 8rauner, R. 6yufk0, D. K016ert, 8. v0n Kr11chten, D. Ryche1, C.-A. W1edner and 5.7.7h0rnt0n, Pr0c. 7th 1ntern. C0nf. 0n At0m1c ma55e5 and fundamenta1 c0n5tant5 (AMC0-7) (Darm5tadt, 1984) p. 75. [7] R. 6yufk0, D. Ryche1, M. 5teck, C.-A. W1edner, R.L. Park5 and 5.7. 7h0rnt0n, Phy5. Lett. 8 150 (1985) 335. [8] P. 71demand-Peter550n, E. Runte, W.-D. 5chm1dt-0tt and U.J. 5chrewe, 2. Phy5. A 320 (1985) 405. [9] U.J. 5chrewe, D. D0rnh13fer, E. Runte, W.-D. 5chm1dt-0tt, P. 71demand-Peter550n and R. M1chae15en, 2. Phy5. A 320 (1985) 595. [ 10] A.H. Wap5tra, 6. Aud1 and R. H0ek5tra, Nuc1. Phy5. A 432 (1985) 185. [ 11 ] 5.W. Yate5, R. Ju11n, P. K1e1nhe1n2, 8. Ru610, L.6. Mann, E.A. Henry, W. 5t6ff1, D.J. Decman and J. 810m4v15t, 2. Phy5. A 324 (1986) 417. [ 12] R.D. Macfar1ane and R.D. 6r1ff10en, Phy5. Rev. 130 (1963) 1491.
RELA71VE E N E R 6 1 E 5 0 F 7 H E 0 F 1477682AND 151H084
PHY51C5 LE77ER5 8
nh11/2 AND
11 June 1987
n51/2 p-DECAY 1 5 0 M E R 5
C.F. L1AN6, P. PAR15 Centre de 5pectr0metr1e Nuc1ea1re et de 5pectr0metr1e de Ma55e, F-91406 0r5ay, France
P. KLE1NHE1N2, 8. RU810, M. P11PAR1NEN 1 1n5t1tut)~r Kernphy51k, KFA Jf111ch, D-5170 J1111ch,Fed. Rep. 6ermany
D. 5CHARD7, A. P L 0 C H 0 C K 1 and R. 8ARDEN 651Darm5tadt, D-6100 Darm5tadt, Fed. Rep. 6ermany Rece1ved 11 Fe6ruary 1987
A1pha-9ammac01nc1denemea5urement5e5ta6115hthe re1at1veener91e50fthe 13-decay150mer51nJ4776 (E~(1.8 m1n)= 50.6(9) kev) and ~JH0 (E~(47 5) =41.4(9) kev) and u = 1.2+ f0r the t51H0 47 5150mer.
1n the 5pher1ca1 nuc1e1 ar0und N = 82 the pr0t0n5 a60ve 2 = 64 f111the 5t/2, h11/2, and d3/2 5he115. Fr0m recent 5y5temat1c 5tud1e5 [ 1 ] 0f the 0dd-2 N = 82 150t0ne5 1t 15 kn0wn that there the 5~/2 0r61ta1 15 the 10we5t-1y1n9 p051t1ve-par1ty 51n91e part1c1e 5tate, and the 5ame 15 e5ta6115hed [2,3] f0r the 0dd-A 76 nuc1e1 w1th 84 and 86 neutr0n5. 0 n e theref0re w0u1d expect that at 1ea5t tw0 13-decay1n9 150mer5 0ccur 1n the 5pher1ca1 0dd-2 nuc1e1 ar0und N = 8 2 w1th 65 and m0re pr0t0n5, and a num6er 0f 5uch examp1e5 are kn0wn. 1n m05t ca5e5 the h19h- and 10w-5p1n 150mer5 can 6e f1rm1y d15t1n9u15hed fr0m the pr0duct10n meth0d and fr0m the1r decay pr0pert1e5, 6ut 51nce they cann0t c0nnect thr0u9h •/-tran51t10n5 1t 15 4u1te d1ff1cu1t t0 determ1ne the1r re1at1ve exc1tat10n ener91e5. 70 kn0w the5e re1at1ve 150mer ener91e515 0fpart1cu1ar 1ntere5t 1n the N = 82 150t0ne5 51nce 5uch data are 0f v1ta1 1mp0rtance t0 determ1ne the pr0t0n 51n91e part1c1e 5pectrum a60ve 2 = 64. A5 Q~-mea5urement5 are 0ften n0t 5uff1c1ent1y accurate, and 5h0rt ha1f 11ve5 0f ne19h60ur1n9 even-2 150t0ne5 exc1ude tran5fer react10n 5tud1e5 1t 15 n0t kn0wn w1th certa1nty f0r any 0dd N---82 nuc1eu5 whether the hj ~/2 Permanent addre55: Department 0f Phy51c5, un1ver51ty 0f Jyv~15ky1~1,5F-40720 Jyv~15ky1~1,F1n1and.
0r the 51/2 51n91e pr0t0n f0rm5 the nuc1ear 9r0und 5tate. 7he N = 82 [3-decay 150mer5 are a150 p0pu1ated 1n a-decay, and 11/2- 15 f1rm1y e5ta6115hed f0r the N = 8 4 a-parent h19h-5p1n act1v1t1e5 fr0m the c0mpet1n9 6 7 [~+ decay 6ranch. A1th0u9h the 5p1n5 0f the 10w-5p1n N = 84 150mer5 are n0t mea5ured 1t 15 a1m05t certa1n that the 10w-5p1n a-decay5 c0nnect t0 the 10w-5p1n 150mer5 1n the N = 82 dau9hter. Accurate Q,-va1ue5 are thu5 kn0wn f0r 60th the h19h- and the 10w-5p1n 150mer5, 6ut a150 the5e data cann0t 5pec1fy the 150mer ener91e5 w1th1n 0ne nuc1eu5. 1n the pre5ent 5tudy 0f 15~H0 a-decay we have n0w mea5ured the re1at1ve 150mer ener91e5 6y 065erv1n9 •/-ray5 1n c01nc1dence w1th weak a-tran51t10n5 t0 exc1ted 5tate5 1n the dau9hter nuc1eu5. 0n1y 1n a few ca5e5 5uch a tran51t10n5 have 6een 065erved 1n rareearth nuc1e1, 6ut n0t 1n c01nc1dence w1th •/-ray5.0ur data 91ve the 150mer1c ener91e5 1n the 0ne-pr0t0n nuc1eu5 1477682 a5 we11 a5 1n the 151H084 parent nuc1eu5 w1th the accuracy 1nherent t0 •/-ray and apart1c1e ener9y determ1nat10n5. 1n add1t10n, the re5u1t5 5tr0n91y 5u99e5t a 1/2 + a5519nment f0r the ~5tH0 10w-5p1n [3-decay 150mer. 7he ~5~H0 act1v1t1e5 were pr0duced 1n the 10n 245
V01ume 191, num6er 3
PHY51C5 LE77ER5 8
~-Decay 0 f
151H0 • 151mH0
11 June 1987
N116 151H°
--~14776
ct-5pectrum
c.4
ct- Pr0jec t10n
×e•.4
0
~"
1
~
1 1200
10~,
-0 0 -0 -4-
200
1600
,
h 2
1 , 3 a - E n e r 9 y (HeV)
1 111
111
11
1111 1
1f1 1
1 1
1111
6ate c~ 2,260
111
LL•11
1
1~ 1111J..
600
1 ~
300
y-Pr0ject10n 0
0 151 75
0
~
0 151Dy
,~
0
00
~
0
0
~
0
1 0
1 200
1 /*00
a-part1c1e 51n91e5 5pectrum 0f f19. 2 wa5 06ta1ned w1th 600 MeV p•5 0n 7 a at 150LDE. 1n the ~5~H0 a-part1c1e 5pectra we c1ear1y 065erve tw0 weak tran51t10n5 w1th E ~ = 4260 a n d 4220 keV 1n add1t10n t0 the k n 0 w n [4] 4606 a n d 4517 keV 11ne5. F r 0 m the c01nc1dence data 1t 15 c1ear that the 1nten5e tran51t10n5 c0nnect the 150mer5, a n d that 60th 5ate111te 11ne5 feed the 354 keV 5/2 + exc1ted 5tate 1n 14776 (f19. 3). F r 0 m 1t5 ener9y, the 4260 keV 11ne c1ear1y 6e10n95 t0 the ~5~H0 10w-5p1n 150mer, and the
~L~ 600
Channe[ Num6er
151 ,, 67 910 8/+
F19. 1. •4776 y-ray5 065erved 1n c01nc1dencew1th the weak cttran51t10n5at 4220 and 4260 keV. 50urce 0f the 0r5ay 150CELE 11 0n-11ne ma55 5eparat0r thr0u9h the (3He, 11 n ) react10n w1th a 1.1 pA 6eam 0 f 2 8 0 MeV 3He 0n a me1ted • 10 9 7 6 tar9et. 7 h e 5eparated A = 151 act1v1ty wa5 c011ected f0r 40 5 0n tape a n d after tran5p0rt mea5ured f0r an e4ua1 per10d w1th a •/-ray 6 e ( L 1 ) a n d a 51 5urface-6arr1er a-part1c1e detect0r 1n c105e 180 ° 9e0metry. Re5u1t5 0f a~/-c01nc1dence mea5urement5 are 5h0wn 1n f19. 1. A n 1ndependent c01nc1dence exper1ment at the 6 5 1 0n-11ne ma55 5eparat0r u51n9 the 96M0(58N1, 3p) pr0duct10n react10n c0nf1rmed the5e f1nd1n95. 7 h e 246
11~111~ 5
F19.2. A1phapart1c1e51n91e5-5pectrum0f ma55 5eparated A= 151 act1v1t1e5 pr0duced w1th 600 MeV p•5 0n 7a mea5ured f0r 60 5 after 1 5 c011ect10nt1me. U a5519nment5are 1nd1cated f0r the tran51t10n5fr0m c5]H0(47 5, 1/2 + ) and ~5~H0(365, 11/2- ). 7he 0.5% 10w-ener9y5h0u1der1nthe 11ne5hape15an e1ectr0n1cart1fact.
C0
.
,
0
6ate c~ t~220
0
1 1+
~ .4
102
t, 11111 11 11
~
100
1 E~ 1
11111
~
1
1 1300
N~ ~
0
3~
7w=365 0
7/2"
72/
3/2 , ~ . ~ p 1.6h
~0~0/ ~.~ .... • 13*
1/*7 71~
651u82
F19. 3. 150mer1cexc1tat10nener91e51nJ4776and 15~H0fr0m J51H0 a-decay. Re1at1vect-tran51t10n1nten51t1e5are 91ven1nparenthe5e5.
11 June 1987
PHY51C5 LE77ER5 8
V01ume 191, num6er 3
4220 keV 11ne mu5t 6e attr16uted t0 15tH0 11/2decay and theref0re can 6e u5ed t0 determ1ne the re1at1ve 150mer ener91e5. 7 h e a6501ute ener91e5 0f the three 1nten5e 11ne51n f19. 2 are kn0wn [ 4 ] t0 + 3 keV, 6ut 1n the pre5ent c0ntext we 0n1y need t0 kn0w the re1at1ve ener91e5 0f the 1nten5e and the 5ate111te tran51t10n5, where the 5eparat10n 6etween the 4606 annd 4260 keV 11ne5 fr0m ~-ray data 15 kn0wn t0 +0.2 keV accuracy. W1th the re5u1t E~(11/2-, 11/2)-E~,(11/2-+5/2)=295.5(9) keV we 9et the exc1tat10n ener91e5 Ex(1 1/2-, 14776) = 5 0 . 6 ( 9 ) keV, and Ex, (1/2 +, 151H0)=41.4(9) keV, where the uncerta1nty 5tem5 ma1n1y fr0m the 11m1ted accuracy 0f the 5ate111te peak p051t10n5. 0 u r va1ue f0r the 11/2- ener9y 1n 14776 15 at var1ance w1th a h19h-re501ut10n ~-ray 5tudy [ 5] wh1ch p1aced the 1/2 + 150mer 50 keV a60ve the 1 1/2- 150mer. 7 h e 0n1y 0ther d1rect determ1nat10n 0f the exc1tat10n ener9y 15 a ( 14N, 118e) tran5fer react10n 5tudy wh1ch 9ave [6,7] Ex(11/2) = 110(30) 0r 80(30) keV. Va1ue5 der1ved fr0m mea5ured Q~-d1fference5 5t111 have rather 1ar9e uncerta1nt1e5; a recent mea5urement [8,9] 9ave Ex(11/2) = 130(90) keV. A5 a c0n5e4uence, the 1983 ad0pted va1ue [ 10] 0f 120(30) keV 15 a150 c1ear1y t00 1ar9e. We here c0u1d ment10n that 80(50) keV wa5 5u99e5ted [ 11 ] fr0m exper1menta1 ener91e5 0f pr0t0n part1c1e-h01e 5tate5 1n 1466d and 148Dy. We n0te that the 1nver510n 0f the 150mer5 6etween 14776 and 151H0 15 51m11ar a5 1n the ne19h60Ur1n9 153H0-14976 a-deCay pa1r. 7he 5ame C0nC1U510n Wa5 a1ready made 1n the 0r191na1 5tUdy [ 12] 0f 151H0 a-
decay, 6Ut 1t Wa5 6a5ed 0n the 1nC0rreCt ear1y 5/2 + a5519nment f0r the 10W-5p1n 150mer5. 709ether W1th the re5U1t5 1n ta61e 1 We a150 91Ve 1nten51ty 11m1t5 f0r add1t10na1 Un065erved a-tran51t10n5 t0 10w-1y1n9 14776 5tate5. 7 h e 1a5t c01umn c0nta1n5 1nten51ty rat105 fr0m 6arr1er penetrat10n ca1cu1at10n5 w1th the re5pect1ve/-va1ue5, 6ut 1t 15 c1ear that 5uch ca1cu1at10n5 91ve upper 11m1t5 f0r the 1~ 0 11ne5 51nce a chan9e 0f the 51n91e part1c1e c0nf19urat10n w111 cau5e add1t10na1 retardat10n. Fr0m the5e num6er5 0ne w0u1d expect a rather 1nten5e 1/2 + --,3/2 + 5ate111te 11ne. 7 h a t we d0 n0t 065erve 1t can 6e under5t00d 51nce the d3/2 5he1115 0n1y part1a11y f111ed 1n the 15~H0 parent nuc1eu5, wherea5 the d5/2 5he11 15 fu11y 0ccup1ed and theref0re the k1nemat1ca11y weaker tran51t10n 15 065erved. A5 wa5 ment10ned a60ve, the 5p1n va1ue 0f the ~5tH0 10w-5p1n 150mer 15 5t111 unc1ear, and a pr10r1 1/2 + 0r 3/2 + 5h0u1d 6e c0n51dered. 7 h e 3/2 + a1ternat1ve 15 c1ear1y 1nc0mpat161e w1th the 065erved a1nten51t1e5, 51nce 1n th15 ca5e the 1=0 tran51t10n t0 the 253 keV 3/2 + exc1ted 5tate 1n 14776 5h0u1d have at 1ea5t 13% 0f the 9r0und 5tate tran51t10n 1nten51ty wh1ch 15 c1ear1y ru1ed 0ut 6y exper1ment. Ana1090u5 c0n51derat10n5 a150 exc1ude the 0r191na1 5/2 + a5519nment f0r 10w-5p1n 151H0. 1n c0nc1u510n we have determ1ned fr0m u7-c01nc1dence mea5urement5 w1th h19h accuracy the re1at1ve ener91e5 0f the n5~/2 and rtht 1/2 13-decaY 150mer5 1n the 0ne-pr0t0n nuc1eu5 14776. 0Ur re5u1t5 501ve 1nc0n515tenc1e5 0f ear11er determ1nat10n5 wh1ch emp10yed d1fferent techn14ue5 that have much 1ar9er
7a61e 1 A1pha-tran51t10n51ndecay 0fN= 84 J5~H0(475, 1/2 +) and ~5~H0(365, 11/2 ) t010w-1y1n9J47761eve15. E~ (keV)
Re1at1ve 1nten51ty
4604 a) (4558) 6) (4359) 6) 4260 c~
100 < 1.1 <0.05 0.26(2)
4517 a) (4565) 6~ (4318) 6~ 4220 c)
100 <0.7 <0.01 0.036(4)
1:-,1r
E~
1
7,,,re~c~"c
1/2 +-, 1/2+ 1/2+-011/2 1/2+~ 3/2 + 1/2+--* 5/2 +
0 51 253 354
0 5 2 2
100 2.2 2.3 0.62
11/2---+11/211/2-~ 1/2 + 11/2---* 3/2 + 11/2--, 5/2 +
51 0 253 354
0 5 5 3
100 4.4 0.19 0.37
a>Fr0m ref. [ 4]. 6) 7ran51t10n n0t 065erved. c) Uncerta1nty f0r ener9y d1fferencet0 1= 0 tran51t10n 150.6 keV. •247
V01ume 191, num6er 3
PHY51C5 LE77ER5 8
uncerta1nt1e5. 7 h e pre5ent d a t a 91ve a150 a prec15e exc1tat10n ener9y f0r the ~51H0 10w-5p1n 150mer a n d d e t e r m 1 n e 1t5 5p1n a5 1/2 + . We t h a n k 0 . K1epper a n d R. K1rchner f0r the1r he1p dur1n9 the exper1ment5 at 6 5 1 , a n d 6 . Wa1ter, A. H u c k , C. R1chard-5erre a n d the ma55 5eparat0r 5taff f0r va1ua61e 5upp0rt dur1n9 a te5t-6eam t1me at 1 5 0 L D E / C E R N . We ackn0w1ed9e e1uc1dat1n9 d15cu5510n5 w1th J. 810m4v15t a n d 0 . 5chu1t.
Reference5 [1] P. K1e1nhe1n2, 8. Ru610, M. 09awa, M. P11par1nen, A. P10ch0ck1, D. 5chardt, R. 8arden, 0. K1epper, R. K1rchner and E. R0eck1, 2. Phy5. A 323 (1985)705. [2] J.A. 521Jc2, M.W. J0hn5 and 8.51n9h, Nuc1. Data 5heet5 46 (1985) 1. [3] P. Kemn1t2, L. Funke, F. 5tary, E. W111, 6. W1nter, 5. E1f5tr6m, 5.A. Hj0rth, A. J0hn50n and 7h. L1nd61ad, Nuc1. Phy5. A 311 (1978) 11.
248
11 June 1987
[4] A. Ryt2, At. Data Nuc1. Data 7a61e5 23 (1979) 507. [ 5] 6.D. A1kha20v, K.A. Me211ev, Yu.N. N0v1k0v, N. 6an6aatar, K.Ya. 6r0m0v, V.6. Ka11nn1k0v, A. P0tempa, E. 51en1aw5k1 and F. 7arkany1, 2. Phy5. A 310 (1983) 247. [6] M. 8rauner, R. 6yufk0, D. K016ert, 8. v0n Kr11chten, D. Ryche1, C.-A. W1edner and 5.7.7h0rnt0n, Pr0c. 7th 1ntern. C0nf. 0n At0m1c ma55e5 and fundamenta1 c0n5tant5 (AMC0-7) (Darm5tadt, 1984) p. 75. [7] R. 6yufk0, D. Ryche1, M. 5teck, C.-A. W1edner, R.L. Park5 and 5.7. 7h0rnt0n, Phy5. Lett. 8 150 (1985) 335. [8] P. 71demand-Peter550n, E. Runte, W.-D. 5chm1dt-0tt and U.J. 5chrewe, 2. Phy5. A 320 (1985) 405. [9] U.J. 5chrewe, D. D0rnh13fer, E. Runte, W.-D. 5chm1dt-0tt, P. 71demand-Peter550n and R. M1chae15en, 2. Phy5. A 320 (1985) 595. [ 10] A.H. Wap5tra, 6. Aud1 and R. H0ek5tra, Nuc1. Phy5. A 432 (1985) 185. [ 11 ] 5.W. Yate5, R. Ju11n, P. K1e1nhe1n2, 8. Ru610, L.6. Mann, E.A. Henry, W. 5t6ff1, D.J. Decman and J. 810m4v15t, 2. Phy5. A 324 (1986) 417. [ 12] R.D. Macfar1ane and R.D. 6r1ff10en, Phy5. Rev. 130 (1963) 1491.