An experimental study of the nuclei 147Sm and 149Sm

Nuclear Physics A103 (1967) 188--202; (~) North-Holland Publishing Co., Amsterdam

Not to be reproduced by photoprint or microfilmwithout written permission from the publisher

A N E X P E R I M E N T A L S T U D Y O F T H E N U C L E I 147Sm A N D 149Sm E. VEJE Physical Laboratory II, H.C. Orsted Institute, University of Copenhaglen, Copenhagen, Denmark

Received 28 April 1967 Abstract: Levels of a47Smand 149Smhave been studied by the (d, d'), (d, t) and, in the case of a~Sm, also by the (d, p) reaction. The measurements were performed at 12 MeV bombarding energy, and the reaction products were analysed in a high-resolution, broad-range, magnetic spectrograph. The ground state transition Q-values have been determined, and a number of previously unknown levels were observed. From the inelastic deuteron scattering cross sections, excitation multipolarities were deduced for transitions to 23 states in 14'7Smand for 28 transitions in 14aSm. NUCLEAR REACTIONS 147,149Sm(d,d'); l*s,15°Sm(d, t); 14sSm(d, p), Ea = 12 MeV; measured ~(Ea.,O), cr(Et,0), o(Ep, 0); deduced Q. 147Sm,149Smdeduced levels, 2, zr. Enriched targets.

|

|

1. Introduction The odd-neutron samarium nuclei have previously been studied by the (d, p) and (p, p') reactions 1). I n f o r m a t i o n has in this way been obtained a b o u t deformed configurations of 151Sm, 153 Sm and 15 s Sin, and a possible candidate for a spherical configuration o f 151Sm has been found. M u c h less is k n o w n a b o u t the nuclei 147Sm and 149Sm, which have 85 and 87 neutrons, respectively, and are thus in the region between a closed neutron shell (N = 82) and Sm nuclei with deformed g r o u n d states (N > 90). In the present w o r k 147Sm and 149Sm are studied by means of the (d, d') reaction and the one-neutron transfer reactions 148Sm(d, t)147Sm, 15°Sm(d, t)149Sm and 14SSm(d, p)149Sm. The combination of the results from the inelastic deuteron scattering experiments and the one-nucleon transfer reactions m a y be useful, because the (d, d') reaction excites collective states of the target nucleus, whereas the one-nucleon transfer reactions preferentially populate particle or hole states of the final nucleus. The experimental technique and the data analysis are described in sect. 2, and the results are given in sect. 3 as follows: The (d, d') results in subsect. 3.1 and the results f r o m the (d, t) and the (d, p) studies in subsects. 3.2 and 3.3, respectively. I n sect. 4, a brief discussion of the present results is given. References to earlier works concerning 147Sm and 1495mm a y be found in ref. 1). 188

ODD-MASS Sm NUCLEI

189

2. Experimental procedure and data treatment The measurements were performed at the Tandem Van de Graaff Laboratory of the Niels Bohr Institute. The deuteron beam from the accelerator was analysed in a 90 ° magnet, deflected by another magnet and focussed by magnetic quadrupole-lens systems through 0.6 × 3.0 m m slits placed 8 cm in front of the target. The beam was stopped in a Faraday cup behind the target, and the current was measured and integrated. The 12 MeV deuteron beam current ranged from 0.7 pA to 1 pA. The targets were prepared by vacuum evaporation of the metals enriched to more than 96 % in the relevant isotope. The enriched isotopes were obtained as oxides from Oak Ridge National Laboratory, Stable Isotope Division, and were reduced 2) to the metals by means of La before the evaporation, which took place from a crucible heated by electron bombardment. The backings were ~ 50/Lg/cm 2 carbon foils. In this way homogeneous targets with thicknesses from 50 to 100 ~g/cm 2 were produced. No change in the properties of the targets was observed during the measurements. TABLE 1 Ground-state transition Q-values Reaction

Q(MeV)

148Sm(d, p)z4~Sm

3.656±0.015

z*sSm(d, t)147Sm

-- 1.890 ±0.015

15°Sm(d, t)149Sm

-- 1.738 ±0.015

The reaction products were analysed in a single-gap broad-range magnetic spectrograph with an average solid angle of ~ 5 × 10 -4 sr [ref. 3)]. The spectrograph was calibrated with alpha particles from 212po. Ilford Nuclear Research Plates with emulsions of the type K2, 25 pm thick, served as detectors. In the (d, d') measurements, the emulsions were covered with 0.1 m m A1 foils in order to absorb tritons and alpha particles originating from deuteron-induced reactions in the target and backing materials. The magnetic rigidities of the proton groups from the possible (d, p) reactions are so small that no proton group has obscured the deuteron spectra below 3 MeV excitation energy. The part of the emulsions which was hit by the protons was in the (d, p) measurements covered with aluminium foils, which reduced the proton energies to roughly 6 MeV and absorbed all other particles. The region of the plates which at higher radii recorded scattered deuterons was covered with 0.1 m m A1 foils. In the (d, t) measurements, the emulsions were not covered with any foils. It was impossible to scan the emulsions for tritons corresponding to excitation energies higher than 2.7 MeV because of numerous deuteron groups with similar magnetic rigidities as the tritons. The emulsions were scanned by counting the particle tracks in + m m wide and 35 m m long strips using calibrated microscopes with a magnification of 250 times. The peak positions were defined as the positions of one third of the maxim u m height on the high-energy sides of the peaks.

190

E. VEJE

TABLE 2 1478m results E x c i t a t i o n energy (MeV) average

(d, d')

).

~

P;. = 2

P2 = 3

2 2 2 2 3 3 3 3 3 2 2 2

----+ + -+ -----

0.20 0.11 0.31 0.04

2 2 2

----

0.05 0.03 0.06

3 3 3 3

-k-k -++

0.03 0.04 0.11 0.03

3

+

0.03

3

÷

0.03

3

+

0.04

3

+

0.03

(d°jd~Q)ca, t~ (/~b/sr)

(d,t)

0

0

0

0.121 0.197 0.716 0.798 0.808 0.931 1.034 1.053 1.066 1.109 1.168 1.172 1.216 1.318 1.346 1.436 1.455 1.542 1.601 1.659 1.718 1.729 1.761 1.776 1.803 1.846 1.868 1.899 1.919 1.946 1.975

0.121 0.197 0.718 0.800 0.810 0.931 1.031 1.054 1.066 1.109 1.170 1.174 1.221 1.320 1.348 1.434 1.454

0.121 0.196 0.714 0.796 0.806

2.055 2.064 2.265 2.374 2.555 2.595

2.055 2.064 2.265 2.374 2.555 2.595

1.036 1.051 1.066 1.165 1.169 1.210 1.315 1.343 1.438 1.457 1.542

0.06 0.13 0.28 0.07 0.14

670 23 150 5 150 ~15 44 29 19

0.15 0.03 0.03

2 2 80 14 2 7 14 190

1.601 1.718 1.730 1.761 1.776 1.803 1.845 1.868 1.899 1.919 1.946 1.975

1.659 1.717 1.728

1.848

140

/

5

~ 9

C o l u m n 1 shows the average values o f the e x c i t a t i o n energies m e a s u r e d in the present work. C o l u m n 2 gives the e x c i t a t i o n energies o b t a i n e d from the (d, d') studies a n d c o l u m n 3 those derived f r o m the (d, t) reactions. The next two c o l u m n s c o n t a i n the e xc i t a t i on m u l t i p o l a r i t y 2 a n d the p a r i t y ~r derived from the (d, d') work. The f o l l o w i n g two col umns s how the e xc i t a t i on p r o b a b i l i t i e s for = 2 and ). = 3 excitations, respectively; the excitation p r o b a b i l i t i e s are defined in the text. The 60 ° cross sections o f the (d, t) reactions m a y be f o u n d in the last column.

191

ODD-MASS Sm NUCLEI

TABLE 3 l " S m results E x c i t a t i o n energy (MeV)

P2=3

average

(d, d')

(d, t)

(d, p)

0 0.02 0.275 0.287 0.348 0.395 0.527 0.557 0.589 0.634 0.662 0.695 0.709 0.785 0.828 0.878 0.920 0.950 0.965 0.988 1.009 1.035 1.047 1.077 1.114 1.122 1.152 1.183 1.193 1.234 1.275 1.303 1.309 1.330 1.345 1.369 1.388 1.422 1.431 1.457 1.475 1.505 1.533 1.544 1.571 1.608 1.631 1.655 1.667

0

0 0.02 0.275 0.288 0.351 0.396 0.529 0.559

0 0.02 0.275 0.285 0.343 0.393 0.525 0.555 0.588 0.631 0.660 0.693 0.71

0.350 0.526 0.590 0.633 0.665 0.696 0.709 0.785 0.828 0.876 0.914 0.948 0.988 1.035 1.046 1.072 1.112 1.121 1.182 1.195 1.235 1.279 1.300 1.330 1.338 1.370 1.394

1.461 1.482 1.505 1.533 1.543 1.573 1.609 1.632 1.654 1.667

0.637 0.661 0.697 0.709

0.877 0.921 0.965 0.988 1.008 1.048 1.080 1.117 1.122 1.151

0.882 0.924 0.953

1.124 1.152 1.184

1.191 1.232 1.304 1.309 1.347 1.371 1.382 1.422 1.431 1.460 1.474

1.539

650 ~20 60 ~25 280 27 180 35

2

--

0.08

2

--

0.03

2 2 2 (3) (3) 3 3 3

---(+) (+) ÷ + +

0.34 0.04 0.40

2

--

0.01

3

+

2 2 2 3

---q-

3 3 2 2 2

qq----

3 3 3 3

q+ + +

0.02 0.04 0.03 0.03

3 3 3

+ q+

0.02 0.02 0.02

3

-?

0.01

2

--

(0.01) (0.01) 0.16 0.09 0.21

0.02

1.010

1.080

1.270 1.305

1.351 1.365

1.450 1.470

1.549 1.569

1,606 1.630 1.657 1.67

(da/d'Q)lo,t~ ( d a / d ~ ) l a , p~ (~b/sr) (,ub/sr)

0.01 0.01 0.02 0.01 0.20 0.10 0.01 0.03 0.03

108 9 53 59

1.0 × 103 ] 300 j 230 170

13 31 13 t 470

J

110 49 70

7 53 11 2 46 210 8 } 6 16

120 310 83

500 5 8 150

12 12 3 3 5 ~11 ~16 75

19 31

t 370

J

~3

0.01

7 7 150

192

E. VEJE TABLE 3

(continued) Excitation energy (MeV) average 1.698 1.731 1.749 1.776 1.817 1.837 1.857 1.885 1.903 1.924 1.940 1.956 1.980 2.029 2.039 2.056 2.083 2.115 2.139 2.176 2.275 2.301

(d, d')

(d, t)

(d, p)

1.690 1.731 1.749

1.698

1.706

1.751 1.771

1.748 1.782 1.816

1,818 1,837 1.857

~b/sr) 2

(pb/sr) ~15 250 120 190

1.885

~50

1.940

200

1.903 1.924 1.956 1.982

1.978 2.029 2.039

2.056 2.083 2.115 2.139 2.176 2.275 2.301

Column 1 shows the average values of the excitation energies measured in the present work. Column 2 gives the excitation energies obtained from the (d, d') studies and column 3 those derived from the (d, t) reactions. The (d, p) excitation energies are found in column 4. The next two columns contain the excitation multipolarity 2 and the parity n derived from the (d, d') work. The following two columns show the excitation probabilities for ,~ ~ 2 and 2 = 3 excitations, respectively; the excitation probabilities are defined in the text. The 60 ° cross sections of the (d, t) reactions may be found in the following column, and the 60 ° (d, p) reaction cross sections are given in the last column.

T h e i n c i d e n t b e a m e n e r g y was c a l c u l a t e d f r o m t h e p e a k p o s i t i o n s o f d e u t e r o n s l e a v i n g the t a r g e t nuclei in t h e first excited state, w h i c h w e r e r e c o r d e d in the s a m e exp o s u r e s as t h e r e a c t i o n p r o d u c t s . T h e e x c i t a t i o n e n e r g y o f the first e x c i t e d state w a s t a k e n f r o m ref. 4). T h e d e u t e r o n b e a m e n e r g y was in this w a y f o u n d t o b e 12.06 M e V in t h e (d, d ' ) m e a s u r e m e n t s a n d 12.11 M e V in t h e (d, p ) a n d the (d, t) r e a c t i o n s . T h e Q - v a l u e s f o r t h e (d, p ) a n d t h e (d, t) g r o u n d - s t a t e t r a n s i t i o n s are listed in t a b l e 1, a n d t h e e x c i t a t i o n e n e r g i e s o b t a i n e d f r o m these e x p e r i m e n t s are g i v e n in tables 2 a n d 3. T h e u n c e r t a i n t i e s in t h e d e t e r m i n a t i o n o f e x c i t a t i o n energies is b e l i e v e d t o r a n g e f r o m + 4 k e V f o r states close to the g r o u n d state u p to +_ 10 k e V for t h e h i g h e s t l y i n g levels. T h e o v e r - a l l r e s o l u t i o n o f the d e u t e r o n a n d t h e t r i t o n s p e c t r a was a r o u n d 10 keV, a n d t h a t o f t h e p r o t o n s p e c t r a was 15 keV. T h e d e u t e r o n s p e c t r a w e r e m e a s u r e d at s c a t t e r i n g angles o f 90 °, 125 ° a n d 150 ° for b o t h i s o t o p e s , w h e r e a s t h e t r i t o n a n d p r o t o n s p e c t r a w e r e m e a s u r e d at 60 ° a n d 90 ° .

193

ODD-MASS Sm N U C L E I

Some of the spectra are shown in figs. 1-5. The spectrograph could be turned around the target without breaking the vacuum or making any change in the target position. In this way the relative yields of elastically scattered deuterons were measured at scattering angles of 30 °, 60 °, 90 °, 125 ° and 150 °. The absolute values of the elastic cross sections were obtained by comparing these yields to the yield of 6 MeV deuterons scattered 30 ° from the target, which was 28

26

24

22

2.0

i

t

r

EXCITATION E N E R G Y MeV 18 16 1& 12 10

08

06

0.4

I

i

[

F

02

00

r

350

3O0

Sm 147 (d,d') 1206 MeV 150° 10000 MC

I

E E 250

~ 200 1

100 so

i 56

tli

Illi

,

, 58

60

li,

P t

!1

62 64 66 68 DISTANCE ALONG PLATE (cm)

~m152

f'(~. I :~L_J 70

72

74

76

Fig. I. Spectrum of deuterons scattered 150 ° f r o m a I 4 7 S m target. The number of deuteron tracks in strip across the exposed zone of the emulsion is plotted against the position along the plate. Groups originating from impurities in the target are labelled by the chemical symbol and the mass number of the impurity. a 0.25 mm

kept at the same position as during the measurements at 12 MeV. The scattering at 6 MeV and 30 ° is believed to be pure Rutherford scattering. The elastic cross sections are given in table 4. The inelastic and reaction cross sections were determined by comparing the intensities of the different groups to the elastic ones. However, as the inelastic and reaction cross sections are from ten to 10000 times smaller than the elastic ones, the elastic groups were recorded on short exposures carried out immediately

194

E. VEJE

before and after the long exposures. The relative intensities of the short and the long exposures were determined from the integrated beam currents. The accuracy of this i n t e g r a t i o n is b e t t e r t h a n 2 %. EXCITATION

2.8

2.6

350

E E

22

20

18

16

ENERGY MeV 14 12 10 08 06 | lili

0'.

02

CO

q

Sm 149 (d,d') 12.06 MeV 150o 10000 pC

300

uo (-4 c5

2/.

250

rY u] 13o9 h£ <.9 < af

200

150

10o L

56

58

60

62 DISTANCE

64 ALONG

66

68

70

72

7Z.

76

PLATE (cm)

Fig. 2. Spectrum of deuterons scattered 150 ° from a a°Sm target. See also caption to fig. 1. TABLE 4 Elastic deuteron scattering cross sections

14~Sm(d, d') 0 30 ° 60 90 125 150

l°Sm(d, d')

dtr/dO(mb/sr)

0

dtr/dO(mb/sr)

8.3 × 103 3.0 × 102 40 9.1 5.5

30 ° 60 90 125 150

8.3 × 102 2.9 × l0 S 42 9.5 5.5

T h e t o t a l i n t e g r a t e d c h a r g e o f t h e d e u t e r o n b e a m w a s f r o m 5 t o 10 m C in t h e l o n g exposures.

]95

O D D - M A S S Srn N U C L E I

o

c~

o

; d',

C~

.o

E >LI.I Z 111

_,

Z

"

ll.

o

o~

X W

Z

0

o0

CD SNO~31N3Q A8 03~nDS80

E 0

.= i;

o

U

e~ 0

co >~ ~:~

m_ o

I

C~

r

o°

I

o

oo

uJwq~

~3d

o

SMDV~I

I

CD

I

I

T

c~

q~

TRACKS

PER o I

0.2Smm o

- -

I

o

o

l

~. 4~

<~

BY D E U T E R O N S

OBSCURED

BY DEU'rERONS

OBSCURED

i i

t,o

0

p~ c~ ~

m x c';

Z

O Z m

0

r~-~-~= L_~ ~_

cD

ag g m

N" o

P~

b~

a r a A "a

96!

ODD-MASS

Sin

197

NUCLEI

3.1. RESULTS OF THE INELASTIC DEUTERON SCATTERING EXPERIMENTS

The excitation energies obtained from the (d, d') measurements are listed in tables 2 and 3, and the cross sections are plotted against the scattering angles in figs. 6-8. The shape of the angular distribution of inelastically scattered deuterons is known to depend on the multipolarity of the excitation of the target nucleus. This dependence has recently been investigated experimentally 5,6) in the even isotopes of samarium. EXCITATION

ENERGY MeV

3.2 30 2.8 2.6 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.402 00 i

i

i

i

i

,

i

i

i

i

L

i

J

p

i

i

[ I

300

Sm lz'8 (d,p)

250

12.1 MeV 90 ° 5000 ~C

200 c;

[3_

150

lOO

i

i i

5O

0

t

3'0

32

!

34 DISTANCE

36

38

40

42

44

ALONG PLATE (cm)

Fig. 5. Proton spectrum from the reaction 14sSm(d, p)149Sm observed at 60 °. See also caption to fig. l.

In these works, it is shown that all angular distributions of multipolarity 2 have similar shapes. Also the angular distribution from the 3- states have a characteristic shape which, however, differs significantly from that of a distribution of multipolarity 2. The excitations of the 4 +, 1 - and 5- states do not show similar regularities of the angular distributions, but they do not have angular distributions with shapes like those of distributions of multipolarity 2 or 3. If these empirical results tentatively are applied to the present set of data, the excitation multipolarity is found to equal 2 for the levels given in fig. 6 and to equal 3 for the states shown in fig. 7. The excitation multipolarities determined in this way are also given in tables 2 and 3. It is not possible in a similar way to deduce excitation

198

E.

I

VEJE

i

X= 2 Excitations

1000

•

t

I

Z148 T147 = [149

I

5m147

100 0121

1109

d3~ •

1.168* 1172 1 1 4 3 6 1.318 1.346

10

5m149

0 589

100

0348

1275

13030527 1114

1077

0950 1234 1631

I

90 °

I

125°

I

150"

Otab

Fig. 6. Inelastic de ut e ron scattering cross sections p l o t t e d versus the scattering angle. P oi nt s b e l o n g i n g to the s a me state of the rest nucleus are connected by b r o k e n lines a n d are labelled by the e xc i t a t i on energy in MeV. The sums of the ), = 2 cross sections of each of the t w o odd Sm nuclei are at the top of this figure c o m p a r e d to the c o r r e s p o n d i n g sums f r o m 14sSm a nd 15°Sm. The s ums of the cross sections are labelled by a Z a n d by the ma s s n u m b e r of the target.

O D D - M A S S Sm N U C L E I

199

r

i

1000 t k:3 Excitations

~[ 148

Z ~50 [ 147

~-

100 t

Sm147 100 o34

1053.1066 ~ ' ~ ,

10

1761+1776

1975

.-....~!2~6~

~919 1846

Sm149 100

1183.1193

0878 0785 0825 ~

'

~

.

1330÷!345

10 0 988 1475 1505 ~.°

!

°

"--
F

l,

90*

125 °

150" e Lab

Fig. 7. Inelastic deuteron scattering cross sections plotted versus the scattering angle. See also caption to fig. 6. T h e sums o f the ~. = 3 cross sections are for each o f the two odd S m nuclei c o m p a r e d to the corresponding sums f r o m 14sSm and 15°8m.

200

E. VEJE

multipolarities from the angular distributions given in fig. 8. The magnitudes and angular variations of these cross sections resemble qualitatively those for the 4 ÷, 1and 5 - states of the even Sm isotopes 6), and consequently, the states, the excitation energies of which are given in fig. 8, may consist of a neutron coupled to a 4 +, 1 - or a 5- state of the even Sm isotopes. 100

+

I

I

Sm147

•

" ~ ;

~L0808

10 1803

1868 1216

.121~

101

I

I

Sm 149

-

~.

1533+1 5 .4& '++++'+

10

1~08 0 820 •

1 9'0°

•

] 125"

' ° 150 8tob

Fig. 8. Inelastic d e u t e r o n scattering cross sections plotted versus the scattering angle. See also c a p t i o n to fig. 6.

It has been shown experimentally that the unnatural-parity states of the even Sm isotopes are not excited in deuteron scattering processes 6) (the cross sections for exciting unnatural-parity states are less than 2 pb/sr for 12 MeV deuterons). If this

ODD-MASS Sm NUCLEI

201

selection rule may be applied to the present work, the parity ~rr of an excited state is determined by the parity rcl of the ground state and by the multipolarity 2 of the excitation through the relation ~f = ( - 1 ) ~-1, as the parity of the ground states of 147Sm and 1498m is known to be negative 4). Parity determinations made in this way from knowledge of the excitation multipolarities are given in tables 2 and 3. In these tables the relative excitation probabilities Pa = 2 and Pa = 3 are also given. The relative excitation probability is defined as the ratio between the cross section for exciting the state and the sum of cross sections for all excitations of the same multipolarity. The tabulated values of Pa= 2 and P~= 3 are average values of the results obtained at 90 °, 125 ° and 150 ° . The angular variations of the excitation probabilities are accounted for by the experimental uncertainties. In fig. 6 are also the sums of the cross sections of the 2 = 2 excitations for each of the two odd Sm nuclei compared to the corresponding sums from the even neighbours 14SSm and 1SOSm" The latter sums are taken from ref. 6). A similar comparison is made for the 2 = 3 excitations in fig. 7. These two figures seem to indicate that most of the 2 = 2 and the 2 = 3 strengths have been found in a47Sm and 1~9Sm. In analogue state experiments 7), the 527 keV state of ~49Sm is found to have I = 1. As this state is excited from the ground state, which has spin 7 with a 2 = 2 excitation, its spin must be I3.2. RESULTS OF THE (d, t) REACTIONS The excitation energies and 60 ° cross sections determined from the (d, t) reaction studies are given in tables 2 and 3. Though it was experimentally possible to detect states with excitation energies up to 2.7 MeV, no level with excitation energy higher than 1848 keV in 147Sm and 2039 keV in 149Sm was found in the (d, t) reactions. Between these excitation energies and 2.7 MeV, the upper limit for (d, t) reaction cross sections was 5 #b/sr. The states populated in the (d, t) study are compared to the states excited in the (d, d') work, and whenever an excitation energy determined from the deuteron scatterings equals an excitation energy determined from the (d, t) reactions (within the experimental uncertainties), it is assumed that the same state was observed in both the (d, d') and (d, t) reactions. 3.3. RESULTS OF THE (d, p) REACTIONS The excitation energies and the cross sections at 60 ° obtained from the (d, p) reactions are given in table 3. Many states were found with excitation energies higher than 1.940 MeV in accordance with the findings of ref. 1). However, these states are not included in table 3, as many level distances at excitation energies higher than 1.9 MeV are comparable to or smaller than the resolution of the spectra.

202

E. VEJE

4. Discussion F r o m the w e a k c o u p l i n g model, one w o u l d expect to find in 147Sm a n d 149Sm a c l o s e q y i n g q u i n t e t o f states excited with 2 = 2 excitations a n d with an average excit a t i o n energy a l m o s t equal to the average excitation energy o f the lowest lying 2 + states in the even n e i g h b o u r s (i.e. ~ 500 keV). Similarly one w o u l d expect a septet of 2 = 3 levels a r o u n d r o u g h l y 1100 keV o f excitation, which is the average excitation energy o f the lowest lying, 3 - states o f the even Sm isotopes. I n 147Sm as well as in 149Sm, neither such a quintet n o r a septet is found, as seen f r o m tables 2 a n d 3. S o m e o f the strongly excited states are greatly displaced in energy f r o m the predictions o f the w e a k - c o u p l i n g model. F r o m tables 2 a n d 3, it is f u r t h e r m o r e seen, t h a t m a n y o f the states which are excited strongly in the (d, d ' ) reactions are p o p u l a t e d c o n s i d e r a b l y in the n e u t r o n transfer reactions too. All this indicates t h a t in 147Sm a n d 149Sm there is a rather strong coupling of collective states with particle states a n d hole states. T h e a u t h o r wishes to express his g r a t i t u d e to the University o f C o p e n h a g e n for a research scholarship a n d to Mr. O. H a n s e n for helpful discussions.

References 1) 2) 3) 4) 5) 6) 7)

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