IL NUOVO CIMENTO
States
in
11sSn f r o m
Vo/~. 77 A, N. 4
llTSn(d~ p ) l l S S n
at
21 0ttobre 1983
12 MeV.
E. FROTA-PESS6~_
Centre Brasileiro de Pesquisas -~isicas, CBP.F/CNPff l~ua Dr. Xavier Sigaud 150, t~io de Janeiro, R J (ricevuto il 3 Marzo 1983)
Summary. - - 11sSn energy levels up to _~5.2 MeV excitation energy are studied in the reaction 117Sn(d,p)llsSn. Deuterons had a bombarding energy of 12 MeV. The protons were analysed by a magnetic spectrograph. The detector was nuclear emulsion and the resolution in energy about 10 keV. The distorted-wave analysis was used to determine I values and spectroscopic strengths. The centres of gravity and the sums of reduced spectroscopic factors are presented for the levels when it was possible to determine the S' value. 66 levels of excitation energy were found which did not appear in previous 117Sn(d, p) reactions. 40 levels were not found previously in any reaction giving ~8Sn. The results are compared with the known ones.
PACS. 25.10. -- Nuclear reactions and scattering involving few-nucleon systems.
1. - I n t r o d u c t i o n .
Tin is a m a g i c - n u m b e r nucleus with Z ~ 50. This closed shell of protons reduces t h e effects of the n e u t r o n - p r o t o n residual interation in n e u t r o n transfer reactions and makes t h e theoretical calculations more reliable. Tin has also a large n u m b e r of stable isotopes. Thus we can m a k e a systematic s t u d y using t h e m as t a r g e t to c o m p a r e changes in nuclear structure using, for instance, n e u t r o n transfer reactions. I n t h e present p a p e r we s t u d y t h e 117Sn(d, p)l~sSn reaction with incident 12 MeV deuterons. Our resolution, in energy, is a b o u t 12 keV for 1~8Sn excited states. We analyse excitation energies from 0 to 5.2 MeV. 25
-
II
Nuovo
Cimerdo
A.
369
370
E.
FROTA-PESSOA
N e u t r o n transfer reactions leading to 118Sn as final nucleus were studied previously b y m a n y authors (~-6). Inelastic scattering (?.14), Coulomb excitation (~5), EC dee~y (le,17), ~-deeay (19,1s.21) and 11~Cd (a, 2ny) (~.2,) giving nsSn were also studied. W e m a k e a comparison of ours with other experimental and theoretical results. I n t h e present work m a n y new energy levels were discovered, including states of small cross-section. This results from t h e fact t h a t we have high resolution in energy, t h a t the (~sum m e t h o d ~ (*) was used and also t h a t unexplored regions of 118Sn excitation energies were examined.
(1) L. R. ~ORRIS and C. F. MOORE: Phys..Rev..B, 136, 40 (1964). (2) E. J. SCHNEID, A. PRASKASH and B. L. COHEN: Phys. l~ev., 156, 1316 (1967). (a) K. YAOI, Y. SAJI, T. ISHIMATSU, u ISHlZAKI, M. MATOBA, Y. NXKAJIMX and C. Y. HUANG: J. Phys. See. Jpn., 24, 1167 (1968). (4) J. H. BJ~.RREGXXRD, O. HANSEN, O. NATHAN, L. VISTISEN, R. CHXPMXN and S. HINDS: Nuel. Phys. A, 110, 1 (1968). (5) D . G . FLEXING, M. BLANN, H. W. FULBRmHT and J. A. ROBBINS: Nucl. Phys. A, 157, 1 (1970). (6) D. G. FLEXING: Can. J. Phys., 60, 428 (1982). (7) B . L . COHEN and R. E. PRICE: Phys. Rev., 123, 283 (1961). (s) D . L . ALLAN, B. H. ARMITAGE and B. A. DORXN: Nucl. Phys., 66, 481 (1965). (9) Y. S. KIM and B. L. COHEN: Phys. l~ev., 142, 788 (1966). (10) D. L. ALLAn: Nuel. Phys. A, 114, 211 (1968). (11) I. KUMABE, H. 0GATA, T. H. KxM, M. INOUE, Y. 0KUMX and M. MATOBA:J. Phys. Soc. Jpn., 25, 14 (1968). (12) T.H. CURTIS, R. A. EISENSTEIN, D. W. MXDSEN,C. K. BOCKELMAN: Phys. Rev., 184, 1162 (1969). (13) G. BRUGE, J. C. FAIVRE, H. F~RAGGI and A. BuSSIi~E: Nuel. Phys. A, 146, 597 (1970). (14) O. BEER, A. EL BECAY, P. LOPATO, Y. TERRIEN, G. VALLOISand K. K. SETH: iVucl. Phys. A, 147, 326 (1970). (15) R. L. ROBINSON, P. H. STELSON, F. K. McGOwAN, J. L. C. FORD jr. and W. T. MILNER: N•el. Phys., 74, 281 (1965). (16) j. HATTULX, E. LUIKKONEN and J. KXNTET.V.: Z. Phys., 231, 203 (1970). (17) W. J. GERACE and G. C. HAMILTON:Phys. Lett. B, 39, 481 (1972). (18) j. KXNTELE and M. KARRXS: Phys. t~ev. B, 135, 9 (1964). (19) L. C. M. DO AM~AL, C. F. DE BARROSLEITE, J. M. F. JERONYMO, A. G. DE PII~HO, D. Russo and S. BAPmOS: Z. Natur]orsch. Teil A, 24, 1196 (1969). (20) j. HATTULA, E. LUIKKONEN and J. KANTELE: Nuel. Phys. A, 125, 477 (1969). (~1) E. SCHW~ZBACH and H. MUNZEL: l~adioehim. Acta, 10, 20 (1968). (22) T. YAMAZAKIand G. T. EWXN: Nucl. Phys. A, 134, 81 (1969). (~3! M. ISHIHARA, R. BRONX and B. HERSK]ND: Proceedings el the International Con]erence on Nuclear Physics, Munich, Vol. 1, edited by J. DE BOER and H. J. MANG (Amsterdam, 1973), p. 256. (~4) A. VAN POELGEEST,J. BRON, W. H. A. HESSELINK,K. ALLAART,J. J. A. ZALMSTRA, M. J. UITZlNGER and H. VERHEUL: Nuel. Phys. A, 346, 70 (1980). (*) We discovered this method in 1968 as referred in T. Borello's doctoral thesis (1971) and M. J. Bechara's Master of Science thesis (1973), University of S. Paulo and it was described in other papers (25.27). Our attention was called recently by
STATES IN 11SSn FROM l17Sn(d,p)llsSn AT 12 MeV
371
2. - E x p e r i m e n t a l procedure.
D e u t e r o n s w i t h 12 )/[eV e n e r g y a c c e l e r a t e d i n t h e t h r e e - s t a g e U n i v e r s i t y of P i t t s b u r g h V a n d e G r a a f f a c c e l e r a t o r h i t a t a r g e t e n r i c h e d i n 117Sn. T h i s t a r g e t w a s 80 ~ g / c m 2 t h i c k a n d w i t h a c a r b o n s u p p o r t 20 ~ g / c m 2 t h i c k . T h e t a r g e t c o m p o s i t i o n i n S n i s o t o p e s is g i v e n i n t a b l e I . T h e s c a t t e r e d protons were analysed in an Enge split-pole magnetic spectrograph. TABLE I. -- Isotope composition o] the target. Sn
112
114
115
116
117
118
119
120
122
124
%
0.08
0.04
0.06
2.34
89.2
4.5
1.12
2.16
0.26
0.28
W e u s e d a s d e t e c t o r n u c l e a r e m u l s i o n s of K o d a k t y p e • T B p l a t e s 50 ~zm t h i c k , t h a t w e r e p l a c e d i n t h e f o c a l s u r f a c e of t h e s p e c t r o g r a p h . P a r t i c l e s h e a v i e r t h a n p r o t o n s w e r e a b s o r b e d b y a l u m i n i u m foils. D e u t e r o n s s c a t t e r e d e l a s t i c a l l y w e r e c o n t i n u o u s l y m o n i t o r e d b y t w o l~aI(T1) s c i n t i l TABLE I I . - Bound-state and optical.model parameters used in D W U C K ealculatiou.
V (MeV)
Deuteron
Bound neutron
Proton
98.81
(a)
(*)
r o (fm)
1.15
1.25
1.25
a o (fm)
0.81
0.65
0.65
w D (MeV)
17.3
13.5
r D (fm)
1.34
1.25
a D (fm)
0.68
0.47
r e (fm)
1.15
Vso (MeV)
1.25 ~so ----25
7.5
r~o (fm)
1.25
aso (fm)
0.47
(*) V=53.3+
27 (Nsn -- Zsn) 0.dZsn 118 § l~--0"55Ep'
where Sn indicates 11SSn. (a) Adjusted to reproduce the neutron binding energy.
O. DIETSOH to a paper (28) where a similar method was used in a small energy interval and for n e a r b y exposure angles. (25) T. BOR~.LLO-Lv.wIN, E. FROTA-PEssSA, C. Q. 0RSINI, O. DIETZCH and E. W . ttAMBURG~R: l~ev. Bras. 2'is., 2, 157 (1972). (26) T. BORV.LLO-LV.WIN, C. Q. 0RSINI, O. DI~TZCH and E. W. HAMBURGER: Nucl. Phys. A, 253, 55 (1975). (27) M. J. BECHARA, O. DIETZCH: Phys. 1~ev. C, 12, 90 (1975). (as) j . R. ]~ESKINE. W. W. BUECHNER, H. A. ENGE: Phys. Rev., 128, 720 (1962).
372
~. FROTA-PEssSA
lators s y m m e t r i c a l l y located at about 39 ~ with respect to the incident-beam direction. The relative normalization of the (d,p) cross-sections was obt a i n e d from them. The absolute normalization of cross-sections was m a d e using t h e 12 MeV d e u t e r o n elastic cross-section on t i n at the m o n i t o r angle (38.7 ~) calculated w i t h t h e code D W U C K (~) using a Saxon-Woods shape p o t e n t i a l with t h e P e r e y - P e r e y (~o) p a r a m e t e r s shown in table II. The plates we o b t a i n e d were exposed only at six l a b o r a t o r y scattering angles from 8 ~ to 45 ~ T h e y were scanned b o t h at S~o Paulo and Rio de Janeiro in 0.2 m m intervals along the plate on Leitz-Ortholux microscopes with 1.25 • • X25 magnification. The distances were measured with an accurate AMES 3223 M clock. Figures 1 gives a t y p i c a l spectrum t h a t corresponds to 27 ~ in t h e laboratory. The energy calibration of ~ o y e r (31) was adopted and the relativistic comp u t e r code S P E C T R E (8~) was used to calculate t h e excitation energy of t h e residual nucleus. I n fig. 1 the peaks in excitation energy of 11sSn are numbered. O t h e r peaks exist t h a t are from 1~8Sn isotopes or other contaminations. I f t h e energy of a peak which appears at all the angles can be accounted for as an isotope already found in tin (d, p) reactions (~,~5-~7)~we can test if it is only an isotope peak. I f the i n t e n s i t y of t h e p e a k is larger t h a n expected, using the values of S or S' given in the referred papers and the t a r g e t composition, t h e p e a k is assumed to be from ~lsSn plus the isotope p e a k which is discounted. To identify the weakly excited levels we used the (( sum m e t h o d ~>. I t was observed t h a t for all tin isotope~ t h e histograms of t h e p r o t o n tracks for t h e Sn(d, p) reaction at two different angles have the peaks uniformly displaced b y constant amount. This results essentially from the fact t h a t , for m e d i u m (as tin) and h e a v y nuclei~ t h e distances between two corresponding peaks are the same (within errors of ours measurements) at all angles if the spectrograph is linear, i.e. if t h e distance of the p r o t o n t r a c k from the edge of the plate is linear in its m o m e n t u m . F o r elements with different mass, however, t h e uniform displacements are different (dependence on t h e recoil nucleus). Figure 2 shows t h e sum spectrum when the corresponding peaks are added together, re-enforcing t h e tin peaks. This is noticeable, when fig. 1 and 2 are compared. Tables III~ IV, fig. 3 and 4 summarize our results and will be discussed later. (39) p. D. K u ~ z : University of Colorado distorted-wave Born approximation computer
code DWUCK and instructions (unpublished). (8o) C. M. P~.Rv.y and F. G. P~REr: At. Data Nuct. Data Tables, 17, 1 (1976). (31) R. A. MoY~R: private communication. (~2) V. B. ~IOORKEAD and R. A. MOY~R: University of Pittsburgh, computer code SPECTRE (unpublished).
STA'fES
IN llSSn
FI~O~I
117Sn(d,p)~lsSn
AT
12 MeV
373
3. - Distorted-wave Born approximation analysis (DWBA). We used t h e D W U C K (29) code for D W B A calculations. The corrections of finite range and nonlocality effects are included in it. The correction p a r a m eters were fld----0.54 fro, fly----0.85 f m and _R-= 0.62 fm. A real p o t e n t i a l well of Woods-Saxon shape corresponding to ro = 1.25 fm, ao = 0.65 fro, ~so = 25 MeV and with the d e p t h adjusted b y the code to reproduce the ~/eutron binding energy, was assumed to bind the c a p t u r e d neutrons. The optical p a r a m e t e r s and bound state employed are given in table II. The reduced spectroscopic factors (1)
S~j - - 2J, ~- 1 S~j 2Jl -[- 1 '
where J~ is the spin of state observed in the stripping process, J, is the spin of t h e t a r g e t nucleus and Szj is t h e spectroscopic factor for the considered state in the (d, p) reaction, calculated using
(2)
, (da/df2)~p (2J, ~- 1) S,~ = 1.53a~w~ ~ ,
where Jn is t h e t o t a l angular m o m e n t u m of the c a p t u r e d neutron, (d(r/d$2)exp is the e x p e r i m e n t a l value of t h e cross-section in t h e first m a x i m u m of the angular distribution which fits our e x p e r i m e n t a l poinls and a~w~A is the D W B A cross-section t a k e n at t h e same point. F o r 1 = 0 the second m a x i m u m in t h e angular distribution is used. The values of 1 alone are not sufficient to define t h e t o t a l angular m o m e n t u m transferred. I t depends also on the level which the n e u t r o n will occupy in the final nucleus. We used the shell model to ascribe the possible t o t a l transferred m o m e n t a . The more probable transitions are to the levels lg~, 2d~, 2d~, 3s89and lh1~ in the n e u t r o n shell 51-82 of 11SSn. We also obtained transitions associated to the 83-126 n e u t r o n shell. The best fits between the angular distribution calculated b y the D W U C K and the e x p e r i m e n t a l ones were found b y trial and error and are shown in fig. 3. :No D W B A angular distribution was accepted if one of the experimental points fells outside twice t h e e x p e r i m e n t a l error from the curve. I f there are two values of 1 t h a t satisfy this criterion, b o t h curves were drawn in fig. 3. I f no / < 5 curve fits t h e data, if more th~n two values of l fit t h e m or if the angular average of da/dt9 is smaller th~n 0.006 mb/sr for a given peak (we~k peak), the curves are not plotted in fig. 3. I n these c~ses we p a t in table I I I as (da/d~9)~. t h e ' h i g h e r e x p e r i m e n t a l value for this pe~k.
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a
J
9
l
II
o
~ o
o ~
0
0
0
q
d
d
d
0
I
III
0
a
I
0
I ~
/ ~
III ~
o
d o
d o
o
I
I
O
9 I
~.. II
11
I
I
I
I
I
d
[
I
o"
0
r
c~
d
~11
d
i
i
i
I
o
L~
0
III
0
d
I [ I
III
I
o c~
0
d
J
I
I
d
d
[
N d
~ d
g d
~y i
0o
I I
o c~
Ill
I
I
I
I
o~ d
I I I
I
i
~ d
I
fl~
d
o c~
0
I I I
i
9
L
(J~/qw)~-p/.~-p:o
ii
9
i
i
r
r
i
r
i
i
I
o
~.
d
o
i
ill
I
i
i
~
r
iii
I
I
i
L
d
d
o
o c~
i 0
t: 0
0
s
382
m. :PP,,o.~A-vm.+ ~ 6+A+
0
u4
III
r
rll 0
0
iI1~1
tllr
0
d
Y
II
I
d
d
~
I
I
I
I
I
f
I
~
c~
c~
o
~.
d
o
ir
I
+
m
i
f
II
r,
i
i
I
,4"
9
r
~
r
rflql
I
I
i 0
d
d
d
II
I
I
I
,
,
r
,
I
i
I: s
I
I
+ I
llll
,
d
0 co
i
r
LC)
r
9
r
r
t+ 0
i
ir
r i r r
o
~(~
d g
d i
0o II
9
i
I
9
Y Ill
d
I
f
,1
I
d
d
~
i lug.)
d
r
,
d
Ii
i i
d
i
i
4
1
i
0
d
I
-
"
-...1"
~ d
I1 I I r i o ~
0 d
d
d
d
'
+
0 ~
d
o
d
/ '
-,~ II
lilt
o d
I I
I
t
f
~
d
iii
0
d
d (us/qw)~'p/..0"P
,
,
r
i
i
o~
o
d
d
d
0
0
' t:
i i I r r r
,
~
i
0
v
0
~0
STATES IN llSSn I~ROM 117Sn(d, p)l~sSn AT 12 MeV
383
e2.
0
i II
I
I
I
I
I
r
i
I I
0
~
~
~.
o
~ o
d
i
i
i
ir
~ o
d
9
i i
I1'
i
0
d
c~
~
'
'
'
'
0 0
d
d
9 i I
!
, ,, III
I I
I
I
I
I
III
o
o~
~o
d
d
d
ir
I I
d
r i
i
d
-4;. II ,4" ~
i
d
d
9
i
I I I I
o
I
I
f
d
II
II
[
c~
.,,,,.
,~
I
I
d
i
I I
I
d
I ~
I
I
I
.
9
d
I
~
..,,,,,
d
d
~ o
~
-
d
d
o
,~o~
O~
<1,
i
i
I
I
/
0
i 0
! I
I I
0
d
d
0
d
d
0
d
9- - .
I i 9 f
"
I
I
I
d
9 *
d
I
d
i
tl
I
9
9 I
I
o
o
d
i i I i i i
I
I
d
I
c;
li
o
.
i
' t;~
'
I
II
0
r i i
i
.7.,7
i I
0
9 I I
I
I
d
f
f
I
I
I
I
II
d
(Jslqu~)6P/#P~
I
r
f
I
d
I
I
II
d
i
T
I
I
I
d
d~
~.
384
~
,
Lc'; u-; ui
.
' o
&,,, ,& d
III
III o
I
I
I
I
I
0
I I
I
I
0
0
d
d
I
{~1
o~
o.
d
o
III
d
J
C~
i
I
9
o"'~ '~o
~
;
cl
d
d
~
I
|
/
I
I
0
III 0
/
9
Ii~I
I
,::,
o
q o
o
~d
d
it
t,l
T
d
IC3
0
~
d
rrr
r s i
n
I c~ 0
d
i
I
,
~
(~,
d
I
u4
q
0
I
9
i
I
111,
~
(Js/q Lu) gp/.o'p ~
t
PROTA-P~S6A
STATES IN 118Sn FROM 1 1 : S n ( d , p ) l l s S n AT 12 I~icV
385
F o r l----2 t h e D W B A curves correspond to Jn t r a n s f e r r e d equal to 3+/2 or 5+/2. I n t w o cases only one of t h e curves agrees w i t h our d a t a . I n all other cases t h e d a t a are in a g r e e m e n t w i t h b o t h curves. I n these cases we o b t a i n S' a n d J = w i t h t h e t r a n s f e r r e d m o m e n t u m corresponding to t h e c u r v e t h a t
0.3Ss
0.12
72
5+ 2
CGxl/3
CG•
0.20.08
0.04
li 32
Ill
0.1-
,llh ,I
0 1.2-
CGxl/2
3" 2
0.04 CGxl/3
0.8-
0.02
0.4-
, lid
0
I i
0
111.20
2
1+
F2
CGxl
0.4-
0.80
CG • I/2
[ 0.2
0.40
b i
0 :r 4
5
0 E~.(MeV)
,
II
,
w I
4
d~ I
5
Fig. 4. - S ~ as a function of E~*. The height of the dashed lines indicated for Ez~ corresponds to ~ Sl~ for each shell model orbital.
fits b e t t e r t h e d a t a a n d is d r a w n in fig. 3. These values are indicated in t a b l e I I I w i t h J ~ in parenthesis. F o r 1 ~ 1, 3 or 5 we used, respectively, t h e J values 3-/2, 7-/2 a n d 11-/2 which is t h e usual, not so convincing, a s s u m p t i o n . I n these cases we p u t , in t a b l e I I I , t h e values of J = in parenthesis. 26 - I I N u o v o Cimento A .
386
E. FROTA-PESSO_&
Comparison o/ experimental results on llSSn levels.
TABLE I I I . nTSn(d, p ) n S S n
r e s u l t s of t h e p r e s e n t e x p e r i m e n t Ed --~ 12 M e V level number
E~ (MeV)
l
J~
0
0.0
0
0+
(da/d~J)m~x (mb/sr)
S'
E, (MeV)
1
S'
1.049
0.449
0.0
0
0.70
1
1.230
2
0,190
0.236
1.22
2
0.39
2
1.758
0
0+
0.188
0.064
1.75
0
0.10
3
2.058
0
0+
0.188
0.062
2.05
0
0.084
4
(2.279)
0.837
2.32
2
1.14
0.172
2.49
0
0.51
2.72
2
1.37
5 (v) 6
7 (~)
2.329
(2 + or 3+)
•d = 15 M e V (2)
0.004
2
(1 + or 2 +) (*)
((2.40S))
2.500
0.720 0.00S
0
0+
0.557
8
{2,577)
0.006
9
2.680
2
(2 + or 3 +)
0.128
0,124
10
2.741
2
1+ o r 2 +
0.802
0.933
11
((2.775))
12
2.817
(5)
(5- or 6-)
0.421
1.202
13 (v)
2.908
(2)
(1 + or 2 +)
0.433
0.445
14
2.933
0
0.064
0.018
15 ( ~ )
2.961
16
2.972
17
((2.991))
0.006
18
(3.020)
0.006
0.010
0+
0.030
STATES IN llSSn ~'~OM 117Sn(d,p)llSSn AT 12 MeV
11~Sn(p, d)nSSn
neCd(cc, 2n)
/~d = (11 --12) MeV (1)
Ep = 20 MeV (6)
Ea :
/~x
E~
E~
(MeV)
(MeV)
0.0
0.0
0+
0.0
0+
1.220
1.23
2+
1.2296
2+
1.750
1.78
0+
J~
2.050
2.05
A d o p t e d levels u n t i l 1976
24 M e V (34)
Jn
(MeV)
2.0424
387
(33)
E~
j:z
(keV)
2+
0+
0.0
0+
1 229.64
4
2+
1 757.8
4
0+
2 043.1
4
(2 +)
2 056.5
6
0+
2 120 2.2803
4+
2 280.33 2310
2.3212 2.320
2.34
5-
2+
2.380
2.4888 2.490
2.53
4+
0+
2321.15
4
4+
10
(3-)
3
5-
2 326.5
3
(1 +, 2 + or 3 +
2 402.6
4
(2 +)
2 405
15
(4 +)
2 488.9
3
(4 +)
2 496.6
5
0+
2.540 2.5749
7-
2 574.83 2 576
2.670 2.730
2 677.4 2.74
(2 +) 4+
2 733.6 2 769
2.810
2810
2.840
2 840
2.860
2 860
2.920
2.8785 2.93
7(4 +)
5
(2 +)
2 725 2.7338
2.890
4 15
(6 +)
(2 +)
3.0521
8+
(4 +)
10
5
2 904
12
(2 +)
7
(2 +)
2 930
(i+
8
2 892
2 929.3
2.9994
(1% 2 + or 3 +)
20
(3 +, 4 + or 5 +)
2 963.6
7
(4 +)
3055.0
25
(8 +)
388
E.
FROTA-PF~SS6A
TABLE I I I (continued).
11vSn(d, p)llSSn results of t h e p r e s e n t e x p e r i m e n t E d ~ 12 MeV level number
E~ (MeV)
19
3.064
20 (v~)
3.141
l 2
Ed = 15 MeV (~)
J:~
(da/d~2)m~ ~ (mb/sr)
S'
E~ (MeV)
l
S'
(2 + or 3 +)
0.049
0.043
3.06
2
0.041
0.018
21 (8)
3.237
0.035
22
{3.264)
0.005
23
(3.274)
0.008
24
(3.286)
25
3.317
26
(3.344)
27
3.363
28 (~)
3.383
0.008 1
3.389
30 (6)
3.409
0.027
0.007
0.008 0 (2)
29
(1- or 2-) 0+ (1 + or 2 +)
0.020
0.006
0.055
0.052
0.020 31
3.423
32
((3.441))
33 (6)
0.006
3.464 (3)
(3- or 4-)
0.045
0.055
34
3.475
35
3.543
(2)
(2+ or 3+)
0.033
0.025
36
3.576
3
(3- or 4-)
0.070
0.085
37
3.597
2
(2 + or 3 +)
0.144
0.109
38
(3.635)
0.007
39
(3.643)
0.006
40
((3.677))
0.005
41
3.721
1
(1- or 2-)
0.169
0.042
42
3.750
1 or 2
(1-, 2-, 2 + or 3 +)
0.039 or 0.033
0.010 or 0.025
3.70
2
0.12
STATV.S IN 11sSn F2aO~t xlTSn(d,p)xlsSn AT 12 M e V
389
xlgSn(p, d ) l l s S n
116Cd(cr2n)
A d o p t e d l e v e l s u n t i l 1976
Ed = (11 --12) M e V (1)
Ep = 20 M e V (6)
E a = 24 M e V (~)
(33)
Ex
E~
E~
E~
(MeV)
(MeV)
J~
J"
(MeV)
J~
(keY)
3.050
3 058
10
3111.5
25
3.130
3137.2
5
3.150
3150
3.1082
10 +
3198
6
3228
14
3240
i0
3254
8
3274
14
3275
7
2+ (10 +) (0 +)
(8 +)
(7-)
3.300
3320
3.340
3337
7
3.360
3369
15
3.380
3380
3.390
3393
10
3 423
7
3.470
3 471
I0
3.520
3 520
20
3.550
3 534
17
3.570
3562
7
3 585
10
(2+)
3 664
14
(4+)
3 698
10
(6 +)
3 700
20
3722
10
3 746
10
3.6919 3.700 '
3.750
(2+)
8+
(4+)
(6 + or 7-)
39G TABL~ I I I
E. FROTA-PESS6A
(continued).
117Sn(d, p)llSSn r e s u l t s of t h e p r e s e n t e x p e r i m e n t E a = 12 M e V level number
E~ (MeV)
E d = 15MeV(2)
1
J~
(da/cl~)m~x (rob/st)
S'
E~ (MeV)
l
S'
(0 +)
0.015
0.003
3.79
3
0.16
(1+ or 2+)
0.078
0.058
3.91
2
0.20
4.04
2
0.13
4.44
2
0.0~
43
3.784
(0)
44
3.819
2
45
{3.857)
46
3.889
(1)
0.007 (1- or 2-)
0.016
0.003
47
3.916
2
(1 + or 2 +)
0.061
0.049
48
3.937
2
(1 + or 2 +)
0.049
0.040
49
3.995
1
(1- or 2-)
0.023
0.006
50
4.046
1 or 2
(1- or 2% 2 + or 3 + )
0.173 or 0.179
0.039 or 0.123
51
4.115
1
(1- or 2-)
0.062
0.015
52
4.136
2
(1 + or 2 +)
0.044
0.036
53
4.203
2
(1 + or 2 +)
0.024
0.019
54
4.233
(3)
(3- o r 4-)
0.023
0.025
55 (6)
4.252 0.030
56
4.288
57 (a)
4.313 0.025
58
4.326
59
(4.352)
0.008
60
(4.365)
0.007
61 (6)
4.391 0.025
62
4.408
63 (v)
4.422
(0)
(0 +)
0.012
0.002
64
4.448
(2)
(I + or 2 +)
0.017
0.012
65 (~)
4.472 (1)
(1- or 2-)
0.038
0.008
66
4.484
67
(4.507)
0.007
STATE8 IN llSSn FROM 117Sn(d, V p ) l l s S n
AT
21MeV
l ~ S n ( p , d)llSSn
116Cd(cr 2n)
E d = ( l l - - 1 2 ) M e V (1)
Ep = 20 M e V (6)
E~ :
Ex
E x
(MeV)
(MeV)
J:~
24 M e V (~a)
E= (MeV)
J~
3.790
3.890
3.910
A d o p t e d l e v e l s u n t i l 1976
(~) E= (keV)
J:~
3 773
16
3 808
6
3 857
10
3 879
14
3 895
10
3910 3.94
4.020
391
4.06
4.12
(2 +)
(2+)
1+, 2 + o r 3 +
3 946
14
3977
10
4014
12
4055
14
4 107
10
4112
6
(2 +) 4 190
4.400
4 420
4.4953
10 +
4 494
(2 +)
7
1+, 2 + or 3 +
392 TABLE I I I
~. FROTA-PESSOA
(continued).
nTSn(d, p)llsSn results of the present level number
E~ (MeV)
experiment l
E d = 12 M e V J~
68
(4.523)
69
4.540
70
4.573
71(e)
4.617
72
4.637
73 (~)
4.696
74
4.706
75
4.798
76
4.832
0
77(v)
4.862
0
78
4.879
0
79(v)
4.940
(3)
(3- or 4-)
3
(3- or 4-)
E d = 15 M e V (~) (da/d~2)m~ (mb/sr)
S'
E~ (MeV)
l
S'
0.008 1 or 2
(1:, 2- or 1 +, 2 +)
0.014
0.003 or 0.010
(I)
(1- or 2-)
0.019
0.005
2
(2+ o r 3 +)
0.082
0.024 0.051
0.043
80(~)
5.006
81
5.014
82
5.025
83(~)
5.043
84
5.068
85(~)
5.098
86
5.116
87(~)
5.142
88
5.150
89
5.163
90(~)
5.181
91
5.193
92
5.208
(0 o r 3)
(0 +, 3 - o r 4-)
0.016 or 0.014
0.003 or 0.012
0+
0.066
0.014
0+
0.025
0.006
0+
0.040
0.008
0.087
0.076
0.067
0.060
0.020 (3)
(3- or 4-)
0.082
0.073
0.011 1 or 2
(1-, 2 - , 1 + o r 2 +)
0.019 or 0.016
0.005 or 0.010
0.090
0.034
The excitation energy in parenthesis m e a n s weak level (da/d$2) average < 0.006. (()) m e a n s very doubtful level (1 + or 2 +) a n d (2 + or 3 +) m e a n s t h a t j n m a y be 1% 2 + or 3 + (see sect. 7). (*) Means strong indication of J n = 3+/2" (~) This level a n d the following one arc m e m b e r s of a n unresolved doublet. (fl) This level a n d the following two are m e m b e r s of a n unresolved triplet. (~) Probable unresolved doublet. (~) I t was n o t possible to fit a n y l ~ 5 curve to iG (6) More t h a n two values of I fit the data.
STATES
IN nsSn FROM nTSn(d,p)nsSn AT 12 M e V
ngSn(p, d)nsSn
n~Cd(a, 2n)
Ea = (11 --12) MeV (~)
Ep = 20 MeV (~)
E~ ~ 24 MeV (24)
(MeV)
E. (MeV)
E~ (MeV)
Jn
Jn
393
Adopted levels u n t i l 1976 (33) E~ (keV)
J~
4 54O
4757
7
4800
4 895
5 040 5 100
(3-)
7
394
4. - Results
x. FROTA-I'ESS6A
and discussion.
The results of excitation energy~ orbital angular m o m e n t u m transferred, t o t a l angular m o m e n t u m and p a r i t y of the observed state, experimental crosssection and reduced spectroscopic factors are summarized in table I I I together with S c h n e i d e t al. (~), Norris et al. (i), Poelggeest et al. (24), Fleming (s) results and the adopted levels from Nuclear D a t a Sheets (3~). Excitation energies (E ), orbital angular momentum (l) trans]erred and ]inal-state spin (J"). - I n table I I I the excitation energies indicated are t h e average of t h e excitation energies at the angles used: 8 ~, 12 ~, 20 ~, 27 ~, 33 ~ and 45 ~ T h e y were obtained b y making use of the focal-plane calibration of the spectrograph and using t h e well-known energy of t h e first level of llsSn ((1229.644-0.04) k e u as reference. The calibration of the spectrograph gives _~ 0.25 ~o u n c e r t a i n t y in the absolute excitation energies. The average value of the standard deviation of excitation energy m e a s u r e m e n t in one of t h e six angles was 3.2 keV (actually from 1.9 keV to 4.5 keV) up to 3.5 MeV. F r o m 3.5 MeV to 5.2 MeV it was 3.4 keV (actually from 1.5 keV to 5.5 keV). We have found 93 levels including all Schneid et al. (2) peaks which were also found b y NORalS et al. (2). All 33 peaks of Norris et al. (2) b u t 2 were also found in the present paper. However, four of t h e m corresponding to 2.540 MeV, 2.840 MeV, 2.860 MeV and 3.150 MeV indeed exist b u t are from isotopic contamination. The first is from 117Sn(0.15~), the following two are from llsSu(g.s, and 0.024), and the last one is from 12~Sn(g.s.) plus 12~ Thus we found 66 peaks which did not a p p e a r in previous 117Sn(d, p) papers (1,2). These ones include 18 weak peaks. F o r the weak peaks only energies and (d~/dl2)m,~ calculated with t h e highest observed point in the angular dist r i b u t i o n arc indicated. W e did not t r y to obtain the 1 values, because we have not enough confidence in the significance of errors in these cases. However, a m o n g the adopted levels (~3) and in a more recent p a p e r (24) eleven of the energy values of these peaks are found. Peaks with orbital-angular-momentum transfer 6 and 7 are unlikely and values larger t h a n 7 are not expected in our case. W e did not find a n u m b e r of the following known excited states (energies in MeV): a) W i t h 1----8 or more: 3.0521, 3.1082, 3.6919 and 4.4953, all of t h e m found in ll*Cd (~, 2n). Also 3.228 ( J - =- (8+)) was found in inelastic scattering. b) W i t h 1-~ 6 or 7 : 2 . 8 7 8 5 (J~----(6+)) was found in ~16Cd(~, 2~) and 3.534 (J~---- (6+ or 7-)) ill iuelastic scattering. Values compatible with b o t h
(33) G. H. CARLSOI%W. L. TAL~RT jr. and S. RAtA)C: Nucl. Data Sheets, 17, 1 (1976).
STAT~S I~ llSSn FROM nTSn(d, p)nsSn AT 12 MoV
395
2.890 a n d 3.550 were f o u n d also b y N o ~ I S et al. (1). T h e t w o e n e r g i e s 2.5749 a n d 3.274 t h a t c o r r e s p o n d to J " = 7- a n d J ~ = (7-), r e s p e c t i v e l y , a g r e e howe v e r w i t h t h e w e a k level energies we found. T h e e n e r g y 2.9994 (J~ = 6 +) (~4) is c o m p a t i b l e w i t h our 2.991 w e a k p e a k . c) W i t h 1 = 5 we f o u n d no p e a k c o r r e s p o n d i n g to 2.32115 f o u n d in " s C d (e, 2n), " S i n ~-decay, '16Sn (t, p) a n d nSSb EC d e c a y . d) As in t h e p r e v i o u s p a p e r s on 'lTSn (d, p) we f o u n d no e n e r g y s u r e l y c o r r e s p o n d i n g to s t a t e s J ~ = 4 +. T h e k n o w n 4 + s t a t e s a r e g i v e n below, b y t h e e n e r g y followed b y t h e r e a c t i o n l e a d i n g t o 11SSn w e r e t h e y w e r e o b s e r v e d : 2.28 033 - Cd (~, 2n), '1Sin ~-deeay, nsSb EC d e c a y a n d nSSn (t, p), 2.405
=
(4+)) - 11sSn (t, p ) ,
2.4889 - n s I n ~ - d e c a y a n d Cd (~, 2n), 2.7336 - 'lSCd (g, 2n), 2.930 ( J " = (4+)) - 119Sn (p, d), 2.9636 (J~ = (4+)) - n s I n ~-deeay, 'lSSn (t, p), 3.471 (J= ---- (4+)) - inelastic s c a t t e r i n g , 3.664 (J~ = (4+)) - inelastic s c a t t e r i n g . T h e energies 2.280 33 a n d 3.664, h o w e v e r , a g r e e w i t h t h e w e a k p e a k s we h a v e . A t 2.930 we f o u n d i n s t e a d a 0 +. T h e e x c i t a t i o n energies 2.961 a n d 2.972 e x i s t in t h e p r e s e n t work, b u t it w a s n o t possible t o d e t e r m i n e t h e 1 values. T h e s e energies a g r e e w i t h 2.9636 ( J ~ = (4+)) g i v e n in (33). A n o t h e r d o u b l e t 3.464 a n d 3.475 v e r y n e a r 3.471 (J~ = (4+)) g i v e n in (aa) a p p e a r s in t h e p r e s e n t w o r k b u t w i t h 1 = (3). T h e v a l u e s 1 = 4 for t h e level 2.576 f r o m 'lSSn ( t , p ) in ref. (as) p. 16 m a y b e a m i s p r i n t : on p. 17 a n d 24 t h a t e n e r g y is r e f e r r e d as l = 7. T h u s it should b e t h e s a m e level as 2.57483 ( J = 7-). W e f o u n d a w e a k p e a k w i t h e x c i t a t i o n e n e r g y 2.577. e) F o r l = 3 we did n o t find 2.310 (J~ = (3-)) f o u n d in C o u l o m b e x c i t a t i o n a n d '~~ (p, t) r e a c t i o n . ]) F o r l = 2 we did n o t find 2.0431 (J~ = 2 + ) f o u n d in '1Sin ~-decay, l'SSb E C d e c a y , 117Sn (~(, n) a n d nsCd (~, 2n) as well as 2.9293 (J~ = (2+)) f o u n d in inelastic s c a t t e r i n g a n d llSSb EC d e c a y r e a c t i o n s l F o r our e n e r g y 3.721 t h a t c o r r e s p o n d s to 3.70 of S c h n e i d et al. (2) we f o u n d 1 = 1 i n s t e a d of 1-----2. g) F o r o u r e n e r g y 3.784 t h a t correspol~ds to 3.79 f r o m SCtINEID et al. (5) we f o u n d l = (0) i n s t e a d of 1 = 3.
396
~. F~OTA-P~SSSA
h) We also did not find 2.120, 3.198, 3.722, 3.895, 4.014 and 4.757 f r o m ref. (33). F o r all these energies there are not indications of J~. Among t h e 93 excitation energies we found, 40 were unknown in 11sSn. These were the following (in MeV): a) 8 weaks levels: 3.020, 3.441, 3.635, 3.677, 4.352, 4.365, 4.507 a n 4 4.523. The level 4.617, the m e m b e r 2.972 of the doublet (2.961, 2.972), t h e m e m b e r 3.409 of t h e doublet (3.409, 3.423), the members of four doublets (4.252, 4.288), (4.313, 4.326), (4.391, 4.408) and (4.696, 4.706) and t h e m e m b e r s of two triplets (5.142, 5.150~ 5.163) and (5.181, 5.193, 5.208) for which it was not possible to determine the l values. b) l ~ 0 : 4 . 8 3 2
and 4.862; l : ( 0 ) :
4.422.
c) l -~ (1): doublet (4.472, 4.484) and one level 4.573; 1 ---- 1 or 2: 5.116. d) 1 ~ 2 :
4.637.
e) 1 ~ 3: one level 5.068 and the members of a triplet (5.006, 5.014, 5.025); l---- (3): one m e m b e r of the doublet (3.464, 3.475), two levels 4.233 and 4.940. Almost all of t h e m are in the less explored region 4.0 to 5.2 MeV. Among the 53 known levels of 11sSn (below 5.2 MeV) we found t h e r e were not previous indication of 1 in 2.2 cases. We found the 1 values of 14 of them (energies in MeV): a) l : 0 :
3.369 and 4.895;
b) l ~ 1 :
3.320, 3.977 and 4.112; l :
c) l--~2: 3.808 and 4.190; 1 : 4.540 ; d) l--~3: e) l :
(1): 3.879;
(2): 3.380, 3.393 and 3.520; 1----1 or 2:
3.562 ;
(5): 2.810.
I u eight cases we also did not find t h e l values. I n 18 of the remaining 31 cases the values of 1 previously determined are compatible with ours, but in 9 eases we could not find t h e 1 values. I n t h e last 4 cases our 1 values are incompatible with the previously known values 2.930 (l~4), 3.471(I:(4)), 3 . 7 0 0 ( 1 = 2 ) and 3.773 ( 1 ~ 3 ) as we found 2.933 (1 -~ 0), a doublet 3.464 and 3.475 (l ~ 3), 3.721 (1 ~ 1) and 3.784 (1 ---- (0)). Our excitation energies are compatible with the corresponding adopted levels, b u t on the average t h e y are a b o u t 4 keV higher. Our energies are ___ 10 keV larger t h a n the energies in SCttNEID et al. and in :NoRris et al. In both papers the first level is at 1.22 MeV, while we t a k e as first level the well-known (a) value (1229.64~=0.04)key (1.230 ~geV).
STATES
IN nsSn
FROM
117Sn(d,p)nSSn AT 12 McV
397
E x p e r i m e n t a l cross-section (da/d~Q)m~x and the reduced spectroscopic ]actor. E q u a t i o n (2) gives t h e values of S' using (dg/dQ)m~. and the corresponding o~waA. The error in ( d a / d ~ ) ~ is ~ 20 % (due to u n c e r t a i n t y in t h e countings of protons and deuterons in the solid angles of spectrograph and monitor and in t h e elastic cross-section adopted). The same error _~ 20 % is expected for o~WBA (34). Thus t h e error in S' is of t h e order of 30 %. F r o m t h e zeroth S c h n e i d e t al. (2) level to the seventh one our values of S' are higher t h a n t h e i r values, b u t t h e y agree within 30% error except the fifth one. :For t h e i r eighth and ninth levels our values of l disagree. Their t e n t h and Swelfth levels also disagree with our in S', but t h e y were separated in more t h a n one level in t h e present work (with higher resolution in energy). We also agree with t h e S' value for t h e S c h n e i d e t al. (2) eleventh level if our 1 is 2. Distribution of spectroscopic strengths. - Using t h e criterions to be explained in this section for t r a n s f e r values we calculated for each shell model orbital lj t h e centre of g r a v i t y E~j: (3)
--
.E*j(Eo) is t h e excitation energy corresponding to a n g u l a r - m o m e n t u m transfer l a n d t o t a l m o m e n t u m t r a n s f e r j. S~j is the spectroscopic strength for this energy. ! Figure 4 shows the values of Sz~ as a function of E*~J and t h e size of the dashed line indicated for each E~j corresponds to ~ SIj found for the corresponding shell model orbital. Table I V gives our results of E~j and ~ Sit t o g e t h e r with S c h n e i d e t al. (2) values and E~j obtained b y us using Fleming (6) data. The sum rule limit appears also in table IV. I a fig. 4 and table I V we considered all the peaks t h a t had some indication for 1. I n five cases we had two possible values of I. In four of t h e m l m a y be 1 or 2 and in one 1 m a y be 0 or 3 (peaks 42, 50, 69, 75 and 86). F o r peak 42 we give l = 2, which is t h e value of Fleming (e). F o r peak 50 also we give 1 = 2, t h e value obtained b y SCHNEID et al. (2) and FLE~rNG (e). Besides our value of S' agrees well with the value of Schneid et al. (2). F o r peaks 69 and 86 we give l = 1 and for peak 75 1 = 0, which corresponds to the more probable curves. The separation in Jn 3+/2 and 5+/2 was m a d e b y taking into account the following: 1) W e found t h e more probable transferred m o m e n t u m for all eases of /----2.
(a4) W. E. FRAI~N: IAEA, Trieste, Lectures (1969).
398
~. rROTA-P~SSSX
2) I n t w o p e a k s of large i n t e n s i t y (5 a n d 10) we o b t a i n e d t h e v a l u e 3+/2 for J . 3) T h e values of t h e c e n t r e of g r a v i t y E~j s h o u l d be t h e s a m e for e a c h o r b i t a l b o t h in (d, p) a n d (p, d) r e a c t i o n s p r o d u c i n g xlSSn. 4) T h e C l e m e n t et al. (CB) (35) c a l c u l a t i o n p r e d i c t s a c o n c e n t r a t i o n of 3/2 s t r e n g t h n e a r 3.0 MeV a n d 5/2 n e a r 4.0 MeV, b o t h s p r e a d i n g in t h e r e g i o n bet w e e n t h e m . W e h a v e t w o large 3/2 p e a k s 5 (2.329) a n d 10 (2.741) a n d t h e l a r g e s t p r o b a b l e 5/2 p e a k s are 37 (3.597) a n d 50 (4.046). 5) W e e x p e c t a Gaussian-like S' d i s t r i b u t i o n . 6) W e a c c e p t w i t h I~LE~I~G (6) t h e t h e o r e t i c a l v a l u e 4.45 of CB (35) f o r t h e e x c i t a t i o n e n e r g y a n d t h e c o r r e s p o n d i n g v a l u e S ' = 3 . i 5 as a f u r t h e r 1 ---- 2 level n o t f o u n d in F l e m i n g ' s e x p e r i m e n t (but f o u n d in ours) as one of his levels t o b e u s e d in t h e analysis. TABI.~ IV. - Values of E~s and ~ S~j. If l = 2 in both papers we attribute our ] transferred to Schneidet al. (2) results. For the Schneidet al. (2) level with 1 = 2 which disagrees with our l = 1 we take our l = 1 (excitation energy 3.70 MeV). Present paper Ed = 12 MeV Excitation energy up to 5.208 MeV
E,,
Sum rule limit = = 2] + 1
Z six
(MeV) lg~
--
E d = 15 MeV Excitation energy up to 4.44 (MeV) (2)
E~j x~sSn from Fleming (6} data
E.
Z s~
E,~
0
--
(MeV) 0
8
--
(MeV)
2d(i )
3.897
0.529•
6
3.96
0.45~-0.08
4.20
2d(~)
2.503
2.729i0.408
4
2.36
2.90•
2.42
1.132
0.807i0.147
3s89
2
1.39•
1.04
> 0
0
--
8
> 3.79
0.16
--
4
> 3.70
0.06
--
lh(~.)
> 2.817
1.202
12
2](~)
> 4.404
0.374
3p(~)
> 3.987
0.094
1.16
W e t h u s p r o c e e d as follows: t h e w e l l - d e t e r m i n e d Jn e q u a l t o 3+/2 are a c c e p t e d f o r our p e a k s as well as for t h e c o r r e s p o n d i n g p e a k s of F l e m i n g (e), t h e s a m e b e i n g d o n e for t h e o t h e r 1 --= 2 levels u s i n g at first t h e m o r e p r o b a b l e v a l u e o f Jn (table I I I , in parenthesis). E~r is calculated for our Jn e q u a l t o 3+/2 a n d 5+/2 b o t h for our p a p e r a n d for l~leming's (see i t e m 6 above). W e t h e n i m p r o v e d t h e a g r e e m e n t of our Ez~ w i t h t h e one o b t a i n e d w i t h F l e m i n g ' s results b y m o v i n g , b y t r i a l a n d error, p e a k s f r o m 3/2 t o 5/2 a n d vice versa. T h e d i s t r i b u t i o n of p e a k s is g i v e n in fig. 4. (35) D. M. CLV.MV,~T and E. U. B ~ A N G ] ~ : Nuel. Phys. A, 120, 25 (1968).
STATES IN 116Sn I~Ro~ 117Sn(d,p)llsSn AT 12 MeV
399
Actually from 18 1-~ 2 levels 9 Jn's did not correspond, in the final classification, to the original more probable values given in table I I I . These are peaks i (for which we had only t h e curve 2d~ to fit our data), 9, 357 44, 47, 48, 52, 53 and 64 (with small average cross-sections (da/d~)m~ x ~ 0.05 mb/sr). The S' given in t h e table for these peaks must be multiplied or divided b y 1.2 if it changes to 3/2 or 5/2, respectively. The peaks for which J~ did not change had average cross-sections (d~/dl2)m~ _~ 0.30 mb/sr. The resulting separation of 3+/2 and 5+/2 corresponds almost to a t t r i b u t e J.----3+/2 for peaks below 3.0 MeV and J ~ 5+/2 for those above 3.0 MeV. I n the shell model the valence neutrons in t h e target, ~TSn, are 17. W e expect t h e m to occur in t h e orbital shell from 50 to 82 and more probably in the lg~, 2d~, 2di and 3689 orbitals. W e had excitation energies up to 5.208 MeV. W i t h our work conditions we expected to find pratically all spectroscopic strengths corresponding to lg~, 2d~, 2d~ and 3689 I f we assume t h a t the m a x i m u m n u m b e r of neutrons in each orbitals is given b y the sum rule limit, ~ Si~ divided by 2 j - { - 1 , table IV gives us the nonoccupation probability in each of these shell-model orbital for the ~TSn ground state. Our results agree v e r y well with Fleming's (6) in the ~TSn(p, d)~16Sn reaction. F r o m their data we obtained t h e occupation probability in each of the referred shell model orbital (table V). The excitation energies ~<3.01 with 1 ---- 2 were t a k e n as 3+/2 transferred m o m e n t u m and the other as 5+/2 in ~6Sn correspondingly to our separation in 1~6Sn. The results for the nonoccupation probability of Schneid et al. (2) are given in table V. For l ~ 0 S c h n e i d e t al. (2) results do not agree v e r y well with ours and Fleming's (6). Actually the occupation and nonoccupation probabilities should add up to one for each orbital when all corresponding reactions are exhausted. In ref. (2) t h e y s t u d y excited states of ~sSn until --~ 4.5 MeV. I n ref. (6) t h e y have excited states of ~lSSn until _ 4 MeV. At these energies we expect t h a t in b o t h cases practically all reactions involving t h e ]gi, 2d~, 2d~ and 36~ orbitals are exhausted. This agrees with t h e fact t h a t we have few and v e r y small values of S' above 4 MeV for these orbitals (fig. 4) and with t h e results in table V. TABLE V. -Nonoceupation probability ((2) and present work) and occupation probability (6). Orbital
Sehneid et al. (3)
present work
Fleming (6)
Nonoceupation probability
Occupation probability
lgz
0.0
0.700 ~- 0.179
2d~
0.075 • 0.013
0.088 • 0.060
0.833 • 0.066
2d~
0.725 • 0.138
0.682 =t=0.102
0.340 • 0.023
3689
0.695 ~- 0.131
0.404 ~= 0.07,4
0.615 ~ 0.044
~0.0
~. FROTX-P~SSSA
400 !
T h e s u m of ~ S~ for t h e considered orbitals in (.o) is 4 . 7 4 • in t h e p r e s e n t work it is 4.0654-0.438 a n d in (6) it is 13.19• These results agree w i t h t h e existence of four holes a n d sixteen valence n e u t r o n s in t h e referred orbitals for t h e 1~7Sn ground state.
5. -
Conclusions.
W e f o u n d 93 levels in t h e r e a c t i o n 1~7Sn (d, p) w i t h 12 MeV deuterons, t h e e x c i t a t i o n energies going f r o m 0 to 5.2 MeV. 66 of these levels h a v e not b e e n f o u n d before in (d, p) reactions. 40 levels were u n k n o w n in a n y reaction leading t o ~sSn (8 of t h e m are w e a k levels). F o r 15 of t h e 32 n o n w e a k levels we f o u n d t h e 1 value. I n the 53 k n o w n e x c i t a t i o n energies of ~18Sn (including 11 w e a k levels) t h a t we found, t h e r e was no indication of 1 v a l u e for 22 cases. I n 14 of these cases we d e t e r m i n e d l. B y a joint analysis of ours a n d F l e m i n g ' s (e) ~7Sn (p, d) results we showed t h a t we h a v e located p r a c t i c a l l y all transitions associated to t h e orbitals lg~, 3dj, ~d t a n d 3s89
W e are i n d e b t e d to E . W . ttA~CBt~GE~ for his interest in this work obt a i n i n g t h e exposure of t h e plates, lending of e q u i p m e n t a n d a p p r o v i n g t h e p a r t i c i p a t i o n of microscopists of t h e I n s t i t u t o de Fisica, Universidade de S~o P a u l o a n d to J. ALZO~A a n d T. CO~aEDO, who did the exposure at P i t t s b u r g h U n i v e r s i t y . W e are t h a n k f u l to T. ]3ORELL0-LEvz~ for m a n y helpful discussions, for supplying us with t h e angular-distribution curves corresponding to our reaction, o b t a i n e d f r o m D W U C K code, a n d for criticisms. Our t h a n k s also to S. JOFFILu for his interest a n d helpful discussions, to Pontificia Universidade Cat61ica do Rio de J a n e i r o for kind h o s p i t a l i t y lodging our labo r a t o r y during t h r e e years a n d to t h e microscopists E. DE L~[A, M. L. L m z , M. MO~AES, L. F. ])E MORA~,S, L. F. l)os REZS, E. T. ROD~IGU~S a n d J. C. ZANELATTO for reading the plates.
9
RIASSUNT0
(*)
Sono stati studiati i livelli di encrgia di 11sSn fino ad un'encrgia di cccitazione di ~5.2 MeV nella rcazione 117Sn(d, p)nsSn. I deuteroni avcvano un'cncrgia di bombardamento di 12 MeV. I protoni sono stati analizzati mcdiante uno spc~trografo magnctico. II rivclatore era un'emulsione nuclcare e la risoluzionc in energia era di circa 10 kcV. L'analisi ad onde distorte i~ stain usata per determinare i valori di 1 e le intensit~ spe~(*)
Traduzione a eura della Redazione.
STAT~S IN ~lsSn FgO~t l~VSn(d, p)~SSn A~ 12 M e V
401
t r o s c o p i c h e . 8i p r e s e n t a n o i c e n t r i di g r a v i t ~ e le s o m m e dei f a t t o r i s p e t t r o s e o p i c i r i d o t t i p e r i livelli q u a n d o ~ p o s s i b i l e d e t e r m i n a r e il v a l o r e d i S ' . Si sono t r o v a t i 66 l i v e l l i d i e c c i t a z i o n e e h e n o n e o m p a i o n o i n p r e c e d e n t i r e a z i o n i ~ S n ( d , 1o). 40 livelli n o n sono s t a t i t r o v a t i p r e c e d e n t e m e n t e i n n e s s u n a r e a z i o n e e h e d h l~sSn. Si c o n f r o n t a n o i risult a t i con quelli n o t i .
CocToanna n ~ s S n n3 p e a ~ m m xXTSn(d, p)118Sn npn 12 M3B.
Pe3mMe (*). - - B pear, uHr~ 11~Sn(d, p)118Sn n p n 3 n e p r n n na)xaiourrrx ~C~TpOttOB 12 M 3 B i4ccne)IymTc~ 3nepreTnaecxHe ypoBHI4 x~SSn BI]JIOTb ~O 3neprnrI BO36ym~eHI4H 5.2 MgB. Y I p o T o ~ I aHa~H3HpyIOTC~ C nOMOtIIbrO MaFHHTHOFO crIeKTporpa~a. ~eTeKTop IIpe~cTaBn ~ e r a~Iepnym 3MyYlbCtlIO H p a 3 p e m e a n e n o 3HepFHH COCTaBJaneT OKOJ]O l 0 K3B. ~ n ~ onpe~enem~a BeYIHqHH 1 I4 cneKTpocKornaqeci~x HHTeHCrmHOCTe~I ~cI~o~m3yeTc~ ana~H3 HCKa)KeHHBIX BOIIH. I'IpI4BO~gTCff I~eHTph[ TH~eCTH H CyMMI~I lapI~Be~eHrmIX crIeKTpOCKOrrrr~ec~.r~x MHOmnTene~ ~ n a nccze~oBaHrmVr y p o s n e ~ , x o r ~ a oKa3~maeTc~ BO3MO~KHblM o n p e ~ e n n T b Beaa~rmy S'. B b m a o6napy~Kerm~ 66 ypoBne~, ~OTOp~e, nO-Bn~nMOMy, n e a a 6 m o a a a n c ~ B n p e ) ~ I ~ y m n x nccneaoBann~rx peaKtm~ l~7Sn(d, p). H a n ~ x 40 ypOBHe~ p a n e e He a a 6 ~ m ~ a n a c b B p e a r t ~ x , I
(*)
HepeaeOeno pec)amlue~.
27 - It Nuovo Cimento A.
