The reactions 64Zn(3He, d)65Ga and 64Zn(3He, α)63Zn

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  • 2 ] Nuclear Ph3~stcs A100 (1967) 416--424, (~) ,North-HollandPubhshtng Co, Amsterdam B 2 G I

    Not to be reproduced by photoprlnt or m~crohlm ,a ~thout ~ruten permtsslon from the puohsher

    THE REACTIONS 64Zn(aHe, d)6SGa AND 64Zn(aHe, ~)6aZn

    M G BETIGERI~, H H DUHM**, R SANTO, R STOCK +** and R BOCK Max-Planck-lnstltut [ur Kernphvsd,, HeMelberg, Germany

    Recmved 11 Aprd 1967

    Abstract The reactmns e'aZn(aHe, d) 65Ga and 6~Zn(aHe, ~)6~Zn have been studied at incident ~He energy of 18 MeV using a broad range magnetic spectrograph and an E-dE telescope Angular d~stnbutmns have been obtained and are analysed by the DWBA theory The results g~*e mformatmn about the ~Zn ground state configuratmn as well as the neutron hole states m ~aZn and the single proton states in nSGa, respectively

    NUCLEAR REACTIONS 64Zn(aHe, d), (~He, ~) E = 18 MeV, measured ~(E, Ot, E "aZn, ('~Ga deduced levels, l, spectroscopic factors Enrmhed target

    1. Introduction

    The nucleus 64Zn has two protons and six neutrons filhng the 2p}, 2p} and If,

    single particle states with the closed fx shell as its core From the small spacing of

    these shell model orbttals, a considerable mlxmg ts expected for the proton as well

    as the neutron configmatlons in the ground state o fZn ~sotopes Most of the prevtous work on 65Ga consisted m the study of ground-state fl-decay *) to levels in 65Zn,

    leading to a ground-state spin assignment of 2 a-- It was, therefore, of mtel est to study the reachon 64Zn(aHe, d)6SGa and to obtain mformatlon regarding the posmons

    of the single proton states and their strengths Recent (p, d) work 2) on Zn Isotopes has provided some mstght into the neutron

    configuratton in these isotopes In the (a He, :~) reaction, higher/-wtlues are kmemat>

    cally favoured and as such the f, hole states can be expected to be more eastly detected

    m the (3He, J) reaction than m the (p, d) reactton, so that m some sense the t\~o

    reactions ate complementary The prevtously knm~n lnformatmn was hmtted to a) fi-decay a) of 63Zn b) energtes of some low-lying levels m 63Zn thzough the study~ s) of the reaction 63Cu(p,n) In the present study, the low-lying levels m

    63Zn upto an exmtat~on of 3 2 MeV have been investigated

    2 Experimental method and results

    The (3He, d) and (~He :~) reactions on 64Zn were studied ~lth the Heidelberg

    Tandem Van-de-G~aaff accelerator using a 3He beam of 18 MeV The zeactlon prod-

    * On lea~e of absence of Atomic Energy Estabhshment Bombay,, India ** Present address Lax~tence Radiation Laboratory, Berkeley, U S

    iF+ Present address Nlels Bohr Institute, Copenhagen, Denmark

    416

  • 64Z; (3 I te ) REACTIONS 417

    aE 200 E

    o ~1C2,

    L)

    I i i

    e4Zn(SHe m)~Zn E3He = 18MeV 25

    I 2

    i !' ]~,

    45 bO 55

    1AOa 12 C I o ao

    is

    "~ Ji s 1 i I 1~

    I' ,., '~ ~/~

    i I

    L I I I 1 I i 60 65 70 75 80 85 90

    Distance along the photo plate

    Fig l The spect rum o f f -par t i c les resul t ing f rom 6~Zn(aHe, ~)6aZn at 25 The numbers on the hnes cor respond to the levels m 63Zn The same number ing ~s also to be found m table I

    1 ~ I I I I I I I

    04 - ~' 64 Zn (3He,O63Zn

    i ~ '~ E3He=18MeV 01~ ',

    ,J_,

    04

    m B ,E, 1

    o41:,,,"

    f ~ ~t_,,_. O1 '~ u, " / - - .

    004~ ~ ~

    O01L I~ I I ~ I

    0 o 20 40 60

    i%

    I I i

    E

  • 418 M G BET1GERI etal

    ucts were analysed by a single gap magnetic spectrograph at forward angles and sam-

    ultaneously by a dE-E telescope at larger angles The resulting magnet spectrum for c~-parUcles at 25 w~th respect to the mcadent beam as shown m fig 1 The numbers on the peaks an the spectrum correspond to the levels m 6 3Zn In figs 2 and 3, the

    64Zn(3He, (x ) l~3Zn , E3He=18MeV

    '1 I I I I I

    1

    O4 E x = 1065

    [=13

    01 ""

    02: ~ " . ~ -

    01 ~q ~,,:

    ~-~ Ex=1216 004 ,~',~

    20 - ~, t=3

    10 ~'- 11.1 |

    04 "~'. Ex=1704

    02 L -~-. [=3 I-E-1

    o Ot 004 {~ Ex=1924

    ,~1~ 002 ' ~ ' ' , ~"~-gF t" 10 * , , "'L

    04 - - - - '4 , , E x = 2 651

    02 ,~ =3

    01 " ' -~=

    \

    004 ~' -

    - E x = 2 764

    . . . . . -,% t=3

    \

    " ' t ~ =3 Z

    - , # EX=2936

    "-~'" ~:~ l __ l ' I ' I Io Ex=3024 -: - x \O

    \ \ :3 - =

    _ " ; , ' . q

    . . . . " l l I \ \ - \ \ z~ \

    E x =3 372

    =3

    001 ; I J I [ i 001 ~ 10" 3(7 50 ~ eCM 10 = 30 50* eCM

    Fig 3 Angular dlstrlbut]ons to the rest of levels m e3Zn The closed circles represent the magnet data and the crosses refer to the telescope data, the dashed curves being the DWBA calculations

    angular dBtnbut lons for the first 14 levels upto an excltaUon energy of 3 23 MeV m 63Zn are shown The closed circles are the magnet data and the crosses represent the

    telescope data The open circles m fig 2 result from an addmonal scattering chamber measurement employing 8 surface barrier detectors Since both the elasncally scattered 3He parncles and the ~-parUcles resulting from the (3He, ~) reacnon are samultane-

    ously recorded an the telescope measurements, normahzataon to absolute umts of cross section was relaUvely easy The error associated with each point in the forward

  • 6aZn(3He) REACT IONS 419

    10 f ~ ,

    64Zn (3He d)65Ga ] i t I

    1()

    4

    2

    10

    O4

    2

    10

    O4

    O2

    01

    4 2 r-ci

    th

    ,E, O4

    oC:~ -ol-o 2

    1

    0,4

    O2

    Ex C~ D

    r 1

    r ~, E x 0062 ,r

    '.

    , - ,~ Ex-O 191

    / ',~ ~ 3

    i l

    Ex=0655

    Xi

    ~ ~ ~ Ex:O 822

    %1 =1

    01~- ,, "~' , Ex=1083

    004~ ,,/f ",.__.,, e:4

    oo2b' ] / k"~4~l I I I I I I

    O 20 40 60 co4

    1

    04

    O2

    1 t 04 / 02 ',

    01

    E3He=18 MeV i I J I I I i I

    E x - ~ ~,70

    X 1

    E x - 1867

    1

    4

    2

    1

    04

    02

    01

    04

    02

    01

    Ex-2034

    d 1~ 4 / ' c

    E x 2 206

    /

    1

    4

    2 E - 2 819

    04 "',,

    2 ~ w, Ex=2 922 'Z

    " ' - . - g2

    04

    02

    2o 4o 6o %M

    Fig 4 Angular dlstribuhons to the levels in ~SGa, the dashed curves being the DWBA calculations

  • 420 M G BET IGERI el a[

    TA~CE 1

    Summary of results obtained in G~Zn(JHe, c~)~3Zn

    Level E,~e l J= S No (MeV) (assumed) (N ~ l 8)

    0 0 1 1- 2 6O 1 0 192 3 5 6 20 2 0 641 1 ~ 1 70 3 1 065 1+3 ~ I " 037/045

    (45~, ' ,155) 4 1 216 3 7 0 36 5 1 704 3 ~ - 0 69 6 1 924 1 ~ - 0 23 7 2 160 weak 8 2 520 weak -- 9 2 650 3 7 1 90

    10 2 760 3 7 - 0 50 11 2 850 3 7,- 0 25 12 2 940 3 r - 0 26 13 3 020 3 7- 0 55 14 3 370 3 ~- 0 87

    Eex e (p, d) S (MeV)

    0 1 35 0 20 2 80 0 64 0 84 1 04 0 70

    1 22 0 25 I 68 0 85 1 91 030

    2 64 0 40

    A normahzat lon factor N ~ 18 2 was used m the calculations

    TABLE 2

    Summary of results obtained m G~Zn(~He, d)~oGa

    Level E~xe l J'~ (2Jr- 1 )5 No (MeV) (assumed)

    0 0 000 1 ~,- 1 34 1 0 062 l }- 1 04 2 0 192 3 ) - 5 05 3 0 655 1 1.~ 0 63 4 0 82l 1 ~ ~ 0 24 5 1 08~ 4 ~ ~ 0 39 6 1 670 1 ~ 0 14 7 1 867 I ~- 0 10 8 2 034 4 q ~ 3 90 9 2 206 3 ~- 0 58

    10 2 819 2 ~+ 0 16 11 2 922 2 2, ~ 0 59

    A normahzatmn factor N -- 4 4 was used m the calculattons

    d l lec t lon is approx imate ly 10~,~, w i th the er ro l s in the backwa ld ang les be ing o f t i le

    o rder o f 20 , ; The resu l t s fo r 6azn ,ue summar ized m tab le 1

    The angu lar d tsmbut Jons fo r the low- ly ing leve ls m SGa resu l t ing f rom the 6aZn

    (3He, d ) react ion are shm~n m fig 4 The cha~acter l s t l c dependence o f the shape o f

    the angu lar d~st r lbut~ons on the angu lar momentum I rans fer can be seen c lear ly , w~th

    l = 1 d tsmbut Jons peak ing at l0 ~, / = 2 d l s t r lb tmons peak ing at 17 5 ~, l = 3 peak ing

    at 25 ~ and I = 4 d~st~lbut lons at 30" The reason x~hy th i s characte l l s t l c dependence

  • 64Zn(3He) REACTIONS 421

    of the shape of the angular d is t r lbunons ~s absent m the case of the (3He, ~) react ion

    has been discussed elsewhere 6) The results for 65Ga are col lected m table 2

    In either case, the energy cal ibrat ion is accurate to _ 15 keV

    3. DWBA ca lcu la t ions

    Theorenca l predlctmns for the react ions 6a'Zn(3He, 3{)63Zn and 64Zn(3He, d )gsGa

    angular d is tnbuUons were obta ined by per forming DWBA calcu latmns using the

    Oak R idge code JUL1E t These are shown in figs 2, 3 and 4 as dashed curves The

    TABLE 3

    Sets of potentml parameters for aHe, ~ and deuterons used m the DWBA calculatmns

    Particles V W r o r e a Vs o r,~ a w 4X W' (Mev) (Mev) (fm) (fro) (fro) (Mev) (fro) (fm) (MeV)

    aHe 165 24 I 3 1 4 0 723 8 1 6 0 81 -- d 87 -- I 15 1 15 0 81 5 1 34 0 68 77 :~ 180 26 1 48 1 46 0 56 - - - - -

    optmal mode l parameters used in the calculatmns are listed in table 3 The aHe

    parameters were obta ined by fitt ing the elastm scattering data 7) on 64Zn at 19 5 MeV

    The start ing values of the parameters were taken f rom ref 7 and were adjusted to Dye

    C -T" ' -V- - - -~- -" -F - - - - " ' -F - - ' r ""~ -~ i i --Y--'-7 - '3 - " -7 - r ' '~

    C4~ 2~ 3 64 _ ,_.n( 'a Hc) ,_q

    04

    02

    01

    -~E, 004

    ~, ,~ 002

    C01

    OO04