E

Nxdear Pltyiics AZ94 (1976) 123-140; ©Narth-Holla~dPia6llaMnp Co., AmaAeridan~xac to be repmdooed bY vhosoDrint or microfilm wlshoas wrltsen permbeion>~ the peblieher

THE GAIVIIVIABAY SPECTROSCOPY OF~P. W. (iRE13N andD. M. 3HSPPARD

Nudear Reseordy Ceam, Unfoaatty 4f.!lberta, Fsbnontovr, .llberta, Conada

Received 17 May 1976

A6strect : The y-rey angular distributions, linear polarization mauler distributions andyy anfiularcorrelation have been measured for tsamitiom observed following the °`Ni(p, n)°`Gis reac-tion. Comparison of the data with the predictions ofthe compound nuclear atatistieal modelyielded the following unique l" assipmwnts for levola iri "üs: 139 loeV (2), 278 ieV (~+) .344 loeV (1 *), 362 keV (3), 609 keV (2), 663 keV (1), 746 keV (3), 878 keV (0), end 893beV (3) .Forthe remaininglevelsbelowP.~ - 1 MeV, probable assianmemts of3741oeV (4), 739keV (2. 3)and927 keV (1) were deduced. Mnltipobmixingsatiwwereobtained for moat oftho transitionsconnecting these levels.

NUCLEAR RFACTlON3 "Ni(p, ny~ E~ 275, 3.00. 3.30, 3.75 MeV; measuredQ(is: ~, . e), rr(e>. >i~poh~rlzation. "c~ deduced le~ela, J, ~, a. Enriched taroet . - -l

1. ïnh+odacdon

Although the doubly odd nucleus 64Cu has been the subject of several experimentalinvestigations in recent years, several uncertainties regarding spin assignments forthe eacitod states ofthis nucleus are still present') . The 63Cu(d, p)6`Cu and 66Zn(d,a)6~Cu measurements of Parkand Daehnick ~) established the level scheme of 6`Cnup to about 3MeVexcitation energy, and their measurements ofthe charged particleangular distributions allowed the assignment of J" limits for most of these states.T'he (n, y) capture work of Shera and Bolotin s) established the y-ray decay schemeand branching ratios for the levels below 1332 keV excitatia~n energy, and tentr~tivç,spin-parity assignments were made based on the assumption that the predominantdecay mode for these levels is via Ml radiation.More recently, several authors have studied the angular distributions and y-y

angular oorrelations of the y-rays emitted following the 64Ni(p, ny)6`Cu re-action ~_ 6). Whilo the results of these works are, for the most part, consistent with,each other, the assignments often conflict with the results deduced from the stripping,and pickup reactions ~).

.

.In order to resolve these ambiguities in the level structure of 6`Cu, we have per-,

formed y-ray angular distribution, linear polarization and angular triple cornlationmeasurements for transitions do-exciting the levels below E_ ~ 1 MeV. Unique spinassignments were obtained for all but three oftheso energy level$, and are summarized .in fig. l. Multipole mixingratios for most ofthe transitions have also been deGec~ntined. .

12s

126

r. w. ox>rax ANn n. M. sz~rrARn

Ex (k~V)

64 Cu

Z. Fgperl>~tal deus

J*t 13130

312.3)

2+412]

3*t

2'

2

Fib. 1. Leveb below 1 MeVexcitation enemy in °~. The spin and parity assignments shown onthe right are those deduced in the present wbri.

Targets for this experiment were prepared by combining powdered nickel metal4enriched to 98 ~ in 64Ni) with a glue formed by dissolving polyurethane in benzeneandsmearing the resulting mixture onto a piece of0.127 mm Ta foil. The targets weretypically 1 to 2 mg/~s thick, and the resulting energy loss of 50 to 100keV for theincident proton beam was assumed to provide sufficient energy averaging over com-pound nuclear states for the compound nuclear statistical model') to be applicable.The targets were mounted at 30° to the incident beam direction, and were bom-

äarded with protons from the University of Alberta CN Van de Crraaff accelerator .Ream currents were typically 300 nA.

aqs eeeeea76

O'Of~f1~0AHOPP~PIP~+l~N~Ofe1~YlOAOP1~0

746739

663

609

374

11111111111111aPO- .naifnPO-nwe~O~Ir100o e~00PA0lVOfal lV O~I w1 P1 ~1ff Pl w~f

e~ee~%ee~~et'eet7eeeee!4"

III~li~llll~il~liül2,a

I39

p0hA.- a

A

Following a preliminary investigation of the yield curve to determine tho decaymodes ofvarious excited states tII 64Cu, four energies were selected for more detailedmeasurements. These energies were 2.75, 3.00, 3.50 and 3.75 MeV, and were chosenso that the levels of interest excited at each energy were not fed by cascades fromhigher levels .

16r

Ô_K 12

NrZ

0e

V

4

0~600

°~ NNl",°1

0°'NtiD.°r)~Cu

Ep " 3.7~ M°V

BY" SS'

S O

N

~N

t~äN~ `°

CHANNEL NUMBER

CHANNEL NUMBER

2.1 . ANC~ULAR DI3TRIBUTION MBA3UREMI:NT'3

2

u

P!~"! Â

>r

700 e00 900 1000 1100

n oN

P

loo 200 300 40o soo 600

1200

Fig. 2. A y-ray sinsks spectrum, meaaared at a proton bombarding energy oP 3.73 MeV end anangle of B - SS°. Transitions in s`Cuare labelled withthe enorgies of the initial sad ßnal levels isthe decay. Contaminant y-rays amlabelled with the auclens from which they originate. Peakslabelled

with a q>metioa mark are ofunidentified origin.

Two different Ge(Li) detectors were used for the measurements. For. the threelower energies the y-rays were detected in a 38 cm3 detector, with a resolution of 3keV (FWHM) for 1.332 MeV photons, while for the measurements at 3.75 MeVincident energy, a 48 cm3 detector, with a resolution of 2.5 keV at 1 .332 MeV, wasused. Measurements were taken at angles of 0°, 31°, 55°, 70° and 90° [ref. s)], eachangle being repeated at least once. A typical y-ray singles spectrum is shown in ßg. 2:For the three lower energies, the intensity of the 770 keVy-ray from the fi = ~'

first excited state of 6 sCu was used as an internal monitor to normalize the runs atdifferent angles . At 3.75 MeV bombarding energy, this transition could not beresolved from the 768 keV y-ray de-exciting the 927 keV level in 6~Cu, and the

d28

P. W. GREENAND D. M. SHEPPARD

intensity of the 663 -~ 0 transition in e~Cu, which was previously measured to beisotropic, . was used as a monitorfor tho moasurenoents at this energy.The measured peak intensities (corrected for absorption in the backing material}

were Shed to the usual Legendre polynomial expansion

A'(9) ' Ao[1 +asPz(cos B)+a,,P~(cos 6)].

The as and a4 coefficients measured in the present work are listed in table 1.TA~ 1

~~~~Polynomial~~

~ as and as for the annular dietrlbutionsmeasured in this work

~.2 . LIIZFAR,PO>AR>~~TION I~ASUREMSNTS

Haro E� is the proton bombarding ~iY, E, the ascitation energy of the initial state in the transi-tion and Fs the aaodtatIon ener8y of the 11na1 states

The linear polarization measurements were performed using aCompton scatteringpolarimeter similar to that described bY Twin et .al. 9). The 38 cma Ge(Li) detectorwasused for the scattering crystal, andtwo7.b cm x 7.6 cm NaIdetectors were usedfor the analyzing crystals, one located in the reaction plane (~ ~ 0°) and the otherperpendicular to the .reaction plane (~ ~ 90°). Tho analyzing crystals were .shieldedfrom direct radiation-from the target by 12.7 cm of lead. A conventional fast-slow

~~ & as

2.75 159 0 -0.29f0.01 O.OOf0.01

3.00 278 0 -0.35f0.01 0.02f0.01344 0 0.01f0.03 0.02f0.03

159 -ao2taa2 -aolfaa~2362 159 -0.42f0.01 0.0~2f0.01

3.30 574 362 -O.ZS.f0.02 0.02f0.02bog o -a3afaol aol fool

159 als.faol -0.01fao2344 -0.27f0.03 -0.04f0.04

663 0 0.00f0.02 0.03fx03278 0.02f0.0~2 x03f0.03344 -o.o2faa~2 o.ooto.o2

3.75 739 159 0.28f0.01 0.02f0.02278 0.28f0.06 0.14f0.07362 -0.11 f0.02 a04f0.03

746 278 -0.39f0.02 0.03f0.02878 0 -O.OSf0.04 0.05 f0.04

154 -0.16f0.15 0.22f0.18344 aoofool -0.02fo.o2

895 159 -0.75f0.03 0.00f0.03278 -0.85f0.14 O.18f0.16

927 278 -0.06f0.08 0.16f0.10

64~'

¢" 0~

1~9

I00 600CHANNEL NUMBER

>~ 3. Sum-coincidence spectra obtained in the avessuroment of linear polarhations. The npPerspectrum was obtained for y-rays Co~toa~cattered om of toe reaction plane (f ~ 90°) and the

lower spectrum for y-tays scattered in the reaction plane (~ .. 0°)"

1000

coincidence circuit, together with a sum-coincidence technique was used to recordthe full energy spectrum of y-rays Compton-scattered into each of the analyzingcrystals . Typical sum~oincidence spectra are shown in fig. 3.

Polarization measurements were also takon at anglos of 0°, 31°, SS°, 70° and 90°,with the measurement at 0° (when the y-rays must be unpolarized) being used tonormalize the results for the different efficiencies of the two analyzing crystals. Fromthe measuredpeak intensities N(A, ~ ° 0°} andN(B, ~ = 90°) isthe sum~oincidencespectra, the linear polarization p(8) can be calculated from s)

where the asymmetry ratio R is a measure of the linear polarization sonsitivity of thepolarimeter. Valves for Rwere calculated by numerical integration over the volumesof the scattering and analyzing cryst~Ls, using a procedure similar to that of Tares

13o

p. w. ax>~NAND D. ~. sz~rrARD

and Maters 1°). The calculated values of R agreed with measurements made for the60~ 4+ ,~ 2+ ~ 0+ angular correlation to within 10 ~, which was the experi-mental error in the measurements. The calculated values ofR used in the analysis ofthe 64Cu pOlarl78tlOII data were assigned the same error. The results of the polari-~ation measurements are summarized in table 2.

2.4. DATA ANALiC3I3 .

TwaLa 2The y-ray linear polariration measne+ed at 6- 90°

The value ofthe asymmetry ratio B is dirwssed is the tent. The theoretical p(B a90°) for all (1', 6)oom~hinad°ms allowed by the annular disMbution measarementa is also riven.

2.3 . ANC~ULAR CORRBLATIONMEASURBMENTS

For the triple correlation measurements, two 7.6 cm x 7.6 cm NaI detectors werepositioned at angles of (B = 90°, ~ = 180°) and (B = 90°, ~ "" 90°), and a 4$ cmaCie(Li) detector was positioned in the reaction plane (¢ = 0°). Coincidence q-raysdatected in the Ge(lâ) detector were routed into different regions of the compeermemory e,ccording to windows set on transitions (from the first four excited states of64~)~~~~~fixed crystals. ~ this way, both the A1 and Cl geometries li)of tl~ correlations were obtained for the y-rays feeding these first four excited states .Both real and random coincidence spectra were recorded simultaneously for each

window, at Cie(Li) angles of 0°, 31°, SS°, 70° and 90°, each angle being repeated atleast once. Each ran was 5-6 hlong. Atypical ~3e(Li) coincidence spectrum is shownin fig . 4.The peak intensities were fitted to the usual Legendre polynomial expansion (1).

Tho a2 anda~ coeffïïcients measured in this work are listed in table 3.

Branching ratios for each level were calcuated by correcting the do coefficient ofeq. (1) for each angular distribution for the efficiency of the Ge(Li) detector, which

278 278 -0.22f0.04 0.37f0.06 2* 0.10 -0.21 f0.022- 0.08 0.19f0.022- 2.14 -0.21 f0.02

344 344 0.06f0.03 0.36f0.06 1+ 0 s04fa011 - ai6 -O.OSf0.012+ -0.19 -0.30f0.032- -0.19 0.30f0.03Y 8.14 -0.21fa02

609 609 -0.34fa14 O.SOf0.03 2* 0.30 -0.12fa012* 1.13 0.18f0.022- 0.23 0.12f0.012- 1.30 -0.22fao2

N

0Ph

0 200 400 600

CHANNEL NUMBER

Tnsra 3

CHANNEL NUMBER

O

1000

REAL & RANDOM COINCIDENCES

Fip. 4. They-rays detected in ooincideance with the 278 -~ 0 transition, which was detected at B ~ 90°and ~ v 180°. Thespectrum was obtained at a bombarding aneray of 3.73 MeV, with the (le(Li) dotoctor at 8 e SS°. The upper spectrum shows the readom coincidences and the lower spectrumshows

the (real-random) coincidences.

ßxperimental Legendre polynomial expansion coe>Ocienta for the Al and Cl geometries ofthe y-yeagnlar oorrelations

Here E,, Es and Es are the enemas of the initial, intermediate and ßnal levols in the cascade.

E1(loeV)

Es(keV)

Es(keV)

Alas as

Clas as

344 159 0 -0.17f0.06 0.10f0.07 -0.13 f0.08 0.07f0.09S74 362 159 -0.39f0.04 0.04f0.04 -0.14f0.10 -0.26f0.11609 159 0 0.44f0.13 0.14f0.15 O.11f0.11 O.OSf0.13663 278 0 -O.18f0.03 0.04f0.03 -0.03f0.03 0.03f0.03739 159 0 0.50 f0.12 -0.07f0.15 0.03 f0.04 0.04f0.05739 278 0 0.46f0.17 0.00f0.18 0.30f0.16 -0.10f0.19746 278 0 -0.46 f0.07 -0.02f0.07 -0.33 f0.05 -0.03f0.05878 344 0 0.27f0.06 -0.02f0.06 0.19f0.14 -O.lOf0.17927 278 0 -0.18f0.05 0.00f0.05 -0.17 f0.06 0.06f0.07

FZ~

Ov.n~

f~

RANDOM COINCIDENCES

200M ô ~

0 m 0Zn fP

ô0"o

0

sa~y

800 erN~ Ip.uYY1~Cun 278 i~V GATE

A1 GEOMETRY600 Ep " 3.75 MTV

B "SS°

132

P. w. (iREBN AND D. M. SHEPPARD

was measured using calibrated sources. For the weaker transitions, complete angulardistributions could not be extracted, and it was assumed that the yield measured atB = 55° was a good estimate of the Ao coe~cient . This will be true if the a~ coei$-cient is small, since Pz(B ~ 55°) ~ 0. The branching ratios determined in this studyand in pravious works are listed in table 4 .The magnetic substete populations for the p-decaying state were calculated using

the statistical compound nuclear computer codo MALADY ia) . Transmission coe~-cients for the proton and neutron channels were obtained from tho computer code

T~s4The y-dec~yy branching rafiot determined in the present work

Hae E, ead Ft are the excitation emergia ofthe initial and ßml levels andEr is the y-ray aaagy"The results of Share aad.Holotln are from ref.'), sad have been corrected for their improper place-ment of the 334 1oeV trandtion (see tmct).

E,(key

E,(key

E~(key

Thiswork

Share andHolotia

139 0 159 100 100278 0 278 100 100344 0 344 96f1 95f2

159 185 4f1 Sf2362 0 362 2f1

139 203 98f1 100574 362 212 100 100609 0 609 82f2 73f5

159 450 8f1 9f2278 331 4f1 lOf3344 263 6f1 8f2

663 0 663 32f2 28f5139 ' ~ 504 27f2 34f6278 385 35f2 29f5344 319 6f1 9f2

739 159 580 77f 1 74f5278 461 . . 6f1 7f2344 395 4f1 2f1362 377 13f1 17f4

746 278 468 100 100g7s o g7a sst2 64f7

139 719 3 f 1344 534 42f2 36f7

89S 0 895 11f4 20f9159 736 40f4278 617 49f4 80f9

927 0 927 (9) 11 f5139 76B (32) 16f4278 649 (59) 73 f6

ABACUS is), using the optical model parameters of Perey 1~) and Hjorkland andFernbach 1 s) .The measured angular distribution and triple correlation geometries for each

transition studied were then used to minimize a total Xs to 8nd acceptable values ofspin and mixing ratio. Since only three polarization measurements were made, theseresults were analyzed separately.

3.1 . DECAY 3CHBME

3. Ezp~tal neaps

The q-ray decay scheme determined from this work is summarized in ßg. 1. Theresults are in good agreement with previous work with the following exceptions.

(i) A weak 362 keV transition is observed, which is assigned as the ground-statebranch of the 362 koY level.

(ü)A719 keV transition is observed, which is assigned as the 878 keYto 159 keVbranch.

(iii) The 534 keV transition, which is assigned by Shera and Bolotin a) as the895 --, 362 decay, is established as the 878 -. 344 transition on the basis of coin«-dence measurements . This assignment is in agreement with that of Davidson et al. 4).

(iv) A 736 keV q-ray is observed, which is assigned as the 895 -. 159 keV dewy.

3.2 . BRANCHINC~ RATI08

Table 4 contains a summary of the branching ratios determined in the presentwork, compared with the results of Shera and Bolotin s). Their results have beencorroded for the improper placement of the 534 keV transition. The two sots ofresults are in good agroement, except for the two highest energy levels .For the 895 keY level, Shera and Bolotin do not observe the 736 loeV transition,

which we find to be comparable in intensity to the branch to the 278 keV level. The736 keV decay was also observed by Davidson et vl. ~), but they give no estimate ofthe relative strength of this branch.Our branching ratios for the 927 beV level are approximate, due to the difiicnlty

in separating the 768 keV transition from the 770 keY q-ray from 6 sCu. Tho resultsof Sham and Bolotia for this level are considered to be more roliablo .

3.3 . TIiE LSVBL3 OF s~

3.3.1 . TheIS9 mrd278keV levels. Both of these levels wore observed to decay onlyto the J` = 1 + ground state. Tho angular distributions ofthe 159 and 278 keV y-raysare very similar, and result in a unique spin assignment of J = 2 for both levels .The linear polarization of the 278 keV q-ray is measured to be p(90°) ~ -0.22

10.04 which, when combined with the angular distribrution measurement, results inthe two possible combinations (J" ~ 2+, 3 = 0.10) and (J" = 2', a v 2.14). Thenegative parity assignment is considered unlikely because ofthe large IVI2/El enhance=

l3a

P.w. a>ta~rl ~xn D. l~. si~PPnaD

meat required, and we, therefore, assign positive parity for this level . The (d, p)measurements of Park and Daehnick ~) indicate positive parity for all levels below 1MeY excitation. Auble') indicates unique 2+ assignments for both the 159 and 278keV levels .3.3.2 . Tlu 3~N keV level. The angular distrib~ions of both the 185 and 344 keY g-

rays were isotropic within experimental errors, and, possible fits were found for spin8of0,1 and 2 . The A1 geometry of the 344 -" 159 -" 0 cascade exhibits an appreciable

T~ sSP~-l~ty assi8nmenta and multipok mixing ratios determined in the present work

Only oomb~inatioms which are consistent with all measm+eme~nts (angular distribadons, linear po"larlzaticn and angular triple oorrolatio~) are ahowm

(rev)r= a

159 o z o.12faoa278 0 2* o.lofo.o2344 0 1 * su values

ls9 1 * o.lofo.lo-7a s a s -3.0

362 159 3 0.06f0.03574 362 2 -4.7 s d s -2.6

4 0.01f0.03609 0 2* 0.30f0.08

159 2* 0.02f0.07278 2* 0.24f0.17

663 0 1 all values278 1 0.07f0.05

-4.7sa~-2.934a l 0.2 s a s s.7

739 159 2 -O.18t0.113 -0.38f0.04

278 2 -0.29 f0.253 -0.43t0.10

362 2 -0.11f0.183 0.57f0.18

746 278 3 0.08f0.03878 0 0

159 0344 0

89S 159 3 0.40f0.13278 3 0.07 sa ~a 2.5

927 278 1 0.04f0.11-s.7 s a s -2.s

3 -0.11 f0.05

40

.GwÇ

so

20

C032 B

tOn~ô

3e2

139

J

2

-90 -43 0 4s 90

133

Flg. S. The measured angular distribution and ,~ carves for the 362 -~ 139 teV t<aasiHon. For thistnsmition, a measurement was taten at 8 ~ 43° instead of B - SS°. The analysis shows a naigne

J - 3 assignment for tbo 36'2 toV level .

negative anisotropy (az Q -0.17t0.06) which eliminates the possibility of J = 0.The linear polarization of the 344 keVq-ray is quite small [p(90°) ~ 0.06f0.03],

while the polari2ations expected for both J = 2 andJ` = 1 - are respectively f0.30and -0.~. The measurements are consistent only with a 1 * assignment.3.3.3 . The 362 and 374 keV levels. The 362 keV levels decays primarily to the 159

keV level, with a weak (2 ~) branch to the ground state also being observed. Themeasured angular distribution and corresponding Xs curves for the 203 keV y-rayare shown in fig. 5. The distribution is very anisotropy (a2 m -0.42f0.01) and the

l36

p.w. ßItEEN Axnn. ~. sz~rrAan

Z4

Oâr

âfV

go.o

aWZr

Fia. 6. The Linear polarization angular distribntioa for the 609 -+ 0 loeV transition. The solid lineschow the expected polarization for diSeQent valves of spin and mixing ratio which Qive a aood fit

to the aasular distribution ofthis decay.

analysis results in a unique spin assignment of J = 3, which is in agreement withtho 3+ assignment of Auble 1) .For the level at 574 keV excitation energy, the only branch observed was to the

362 keV state. Although this transition has been observed by previous authors, noangular distribution measurements havo bean reported . In the present study, both theangular distribution and the 574 -. 362 -. 159 keV angular correlation were mea-sured, and the analysis allows possible assignments of (J .s 4, a = 0.01 t0.03) and

Although a distinction between these possible solutions cannot be made on thebasis of our meas»rem~+ts, the J ~ 4 assignment is preferred for the followingreasons . The level is very weakly populated in the (p, ny) reaction, suggesting thatthe spin is probably > 3 . The fact that the level decays only to the J = 3 state alsotends to oonßnn' the ` assumption . of high spin. Park and Daehnick s) measure anL = 4 transfer in the 66~n(d, a)s4Cu reaction, limiting the spin to 3 + , 4* or 5+ .Auble 1 ) also assigns 4* for this level .3.3.x. The 609 a~td 663 keV leoels. The angular distribution of the 609 keV y-ray

exhibited a large negative anisotropy (a= ~ -0.310.01) and allowed a unique spinassignment of J~ 2 for the 609 keV level, with possible mixing ratios of 8 = 0.3010.08 and b = 1 .1510.25 .Tho linear polarization distribution for the 609 keV y-ray, which is shown in fig. 6,

limits the possiblo choices to (J; a 2+, S = 0.30) and (J` v 2-, 8 = 1 .30) . As inthe case of the .278 keV y ray, the large M2fE1 mixing required for the megativeparity .assignment is considered unlikely, and hence positive parity is assigned forthis . level : Auble I) assigns J` = 2+ for the 609 keV level.

66

Ôv

-0ÔV

0W

AI ßEOMéTRY

CI ßEOMETRY'

i0r

46

42

11 ~+ v ~ ~ 4

0 0.3 tA 0 Q3 1 .0

Fia. 7. The an;ular dietrlbatian of the 663 --~ 278 decay and the A1 and Cl aeometries ~~) of the663 -~ 278 -+0 an8alar correlation. The~curvxa werecalculated usinaatlthreeofthese measae+emeots

Hea+e, d is the mixing ratio for tés 663 -+ 278 beV transition.

Forthe 663 keV level, the measured angular distributions for the 663, 385 and 319,keV y-rays were all isotropic within errors, and possible fits were found for spinâ .of0, 1 aad 2. The A1 and Cl geometries of the 663 -" 278. -~ 0cascade are shown infig. 7. The isotropy of the Cl geometry indicates that tha initial state is not strongl~~aligned, while the negative anisotropy of the Al geometry excludes the J = 0 assign-ment. Simultaneous analysis ofthese measurements ibsultw in a unique J = 1 assign-..ment, which is in agreement with the tentaitive results of Davidson et al. ~) ~ and.Wellborn et al. ') although not with Park and Daehnick ~), who assign J ~ 3 . oathe basis of an L = 4 transfer in the 66Zn(d, a)6~Cu measurements .3.3.3. The 739 anal 746 keV leoels. The ângular distributions of the 580, 461 and,

377 keV q-rays which depopulate the level at 739 keV are all consistent with eitheF

138

P.W. QRESN AND D. M. 3HEPPARD

0 03tCn ~ ô

COi~ 8Al ßEOMETRY

CI ßEOMETRY

O

J "0

cost 8

cost BPla. 8 . The annular dietrib~ion ofthe 878 -~ 344 transition sad the Al and Cl Qeometries ") ofthe878 -+ 344 -~ 0 anaalar correlation. The ~~wei+e calculated mina ell throe of these meseuro-

manta. Here, d is the mixiaa ratio for the 878 -+ 344 decay.

J = 2 or 3 for this level, and no distinction between these can be made on the basisof our measurements.For the 746 keV level, the measurements ofthe angular distribution ofthe 468 beY

transition and the 746 -. 278 -~ 0 angular correlation are consistent only with aJ~ 3 assignment.3.3.6. The 878 keV level. The angular distributions of the 878, 719 and 534 keY

y-days were all isotropic within errors, limiting the spin of the 878 keY level toJ ~" 0, 1 or 2. The A'1 geometry of the 878 -+ 344 -. 0 cascade has az = 0.2710.06,and this positive anisotropy results in J = 0 as the only aooeptable solution (ßg. 8) .The assignment of J ~ 0 is is agreement with Park and Daehnick ~) and Hass and

Stelson t e), but not with Davidson ei al. 4 ) who assign J = 1 as the most probablespin. The absence of strong branches to the low-lying J = 2 levels at 159 and 278

64(~ 139

keV (the 719 keVy-ray is only a 4~ branch, with no decay observed to théZ 78 keVlevel) also tends to support the J = 0 assignment .3.3.7. The 89S ayrd927 keVlevels. Forthe 89S keV level, angular distributions were

measured for the branches to the 159 and278 keV levels . Both ofthese measurementsresulted in a unique J = 3 assignment, which is in agreement with the 3+ assignmentof Auble 1 ).For the 927 keV level, measurements were possible only for the 649 keV transition,

since the branches to the ground state and 159 keV level were obscured by contami-nant peaks (fi& 2) . The angular distribution and 927 -. 278 -~ 0 correlation mea-surements are consistent only with J = 1 or 3 for this level. Park and Daehnick 2)assign J = 1 on the basis of a strong L = 0 transfer in the 66Zn(d, a)64C reaction,while Bass and Stieldon is) find J = 0, 1 or 2. The J = 1 assignment seems morelikely, therefore, although our measurements cannot convincingly distinguish be-tween the two.

5. Conclaeions

lin the present work, the measurement of angular distributions, linear polarizationangular distributions, and angular triple correlations following the 6°Ni(p, ny)64Cureaction has resulted in the assignment of unique spins for all but three of the levelsbelow 1 MeV excitation energy lII 64Cu. The results deduced here are in good agree-ment with those of previous authors in most cases, and have resolved some existingdisagreements concernnng spin assignments.The multipole mixing ratios deduced in our study are in fair agreement with those

of Davidson et al. 4) and Wellborn et al. s ), although our results show significantlymore E2 strength in some cases . This E2 enhancement could indicate the importanceof collective effects in a theoretical description of 64Cu. Indeed, the odd-mass Cuisotopes can be well described in terms of a single proton coupled to a vibrationalcore 1 ~~ 18'~

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