LETTERE AL NUOVO CIMENTO

VOL. 18, N. 3

15 Gennaio 1977

Excitation Functions of (d, d) and (d, p) Reactions on 15~ in

the Deuteron Energy Range E~ = (1.4=...7)McV

(*).

G. C~,v~, S. C~VALL~O and R. :Po'r~,'z~ I s t i t u t i di F i s i c a dell' U n i v e r s i t h - C a t a n i a

F. RIC,GI Centro S i e i l i a n o d i F i s i c a N u c l e a t e e di S t r u t t u r a della M a l e r i a - C a t a n i a C. SPITALERI

I s l i t u t o di Mecca~eica R a z i o n a l e e M a t e m a t i c h e ~lpplieale a l l ' I ~ g e g ~ e r i a dell' U n i v e r s i t ~ - C a t a n i a

(ricevuto il 28 0 t t o b r e 1976).

Nuclear rq'aclions induced by low-energy deuterons on light nuclei are a powerful source of information to study the reaction mechauisms involved in these processes. It has becu shown that ma~iy features of (d, p) reactions on l~ 12C, ~4N and le() (~-4) may t)c we,ll ~ccotutted for by the optional model, Itaus~r-Feshb,~ch theory and distortedwave Born approximation for what concerns the shape cla,~tic scattcril~g, the compoundnucleus contributions and tht~ (d, p) or (d, n) stripping reactions, respectively. However, to perform a complete analysis of one of these rca('tions it seems to be very important the knowledge of thc data relative to all opcn channels that can appreciably contribute to the process. In ~ previous paper (5) we have reported the results of the absolutc-cross-scctioxl lncasurcu~cnts of lSN(d,c~)13C reaction at E d < 3 McV; in this note are reported the excitation functions for (d, d) and (d, p) reactions on ~sN in thc deuteron energy rangc E d-- (1.4 : 2.7) MeV, for 01,~= 71 ~ 109 ~ 128 ~, 146 ~ The aim of the present work is twofold: first to obtain the excit~tien functions in an cnergy region that was not previously investigated for the ~ N nucleus; and, second, comparc these results with those already obtained for the ~N(d, ~)~aC reaction, performed (*) (l) (2) (~) (a) 647 (~) 4:67

Work suplmrtc4 by INFN, CSFNSSI and CRRNSM. ]). E. HODYSON an(1 D. WIL.~IOIr Proc. P/tys. Sot., 90, 361 (1967). A. (L~.LL:~IAN~', F. FINTZ a n d P. E. HODOSON: N*~cl. Phys., 82, 161 (1966). SL. C,~,V,~LL~.RO, A. CIZNSOL(), R . POTE.~ZA ~nd A. RUBBINO: Naovo Cfmento, 14, 692 (1973). R . F. ~EILER C. I t . JONES, W . J . ANZIC~, D. F. HERRING a n d K . W . JONES: N a t l . Phys., 45, (1963). G. CALVl, ~;L. CAVALLARO, it. POTENZ,k, F. I{,I(~G! a n 4 C. S['IT,tLERI: Left. Nuovo Cimento 17, (1976),

77

~8

G. CALVI, S. CAVALLARO, B., POTENZA, F. RIGGI a n d

c . 8PITALI~RI

in the same energy range, to see. w h e t h e r the s t r u c t u r e observed ill (d, o:) excit~tion functions is present also in other channels. Actually, a previous work on this reaction (e), p e r f o r m e d d c t c c t i n g y-rays from the residual nucleus ~SN, has shown some e v i d e n c e for weak resonances at b o m b ~ r d i n g energies near E d = 1.3 MeV and 1.9 ~IeV, corresponding to cxcited states in 170 at 15.2 MeV and 15.7 MeV. A t this low energy of the incident deuterons on light nuclei, one can expect thc direct c o n t r i b u t i o n to the reaction be p r e d o m i n a n t at forward angles; for this reason, in order to test t h e presence of i n t e r m c d i a t c structure in the e x c i t a t i o n functions, wc h a v e perf o r m e d m e a s u r e m e n t s of ( d a / d ~ ) E d essentially at O l ~ . 90 ~ 75

~

50

9

9149

~

"

9

.-

~'..; 9 .. ...~" "...5

Omb=146~

9 .." ;.2...." "...

.;;'.'~"

9

I/)

E

~o

II

I

50

=128o ~.._~

,",,,9

25

0 L_

I

I

I

1.5

2.0 EcL(MeV)

2.5

F i g . 1. - E x c i t a t i o n f u n c t i o n s for t h e douteror~ e l a s t i c s c a t t e r i n g o n ~bN. T h e solid l i u e s r e p r e s e n t tile R u t h e r f o r d c r o s s - s e c t i o n , tSN(d, d ) ~ N .

(6)

N. A. BOSTRO,~t, E. L. IIUDSPETH a n d I. L. MOR(}AN: Phys. ReV., 105, 1545 (1957).

]~XCITATION FUNCTIONS OF (d, d) AND (d, p) R~ACTIONS ETC.

79

T h e e x p e r i m e n t a l p r o c e d u r e was t h e s a m e as r e p o r t e d in ref. (5). A gas t a r g e t , e n r i c h e d to 9 9 . 5 % in 15N was u s e d to m a k e a b s o l u t e m e a s u r e m e n t s of d i f f e r e n t i a l cross-sections A c a l i b r a t i o n of t h e b e a m e n e r g y w a s m a d e b y o b s e r v i n g t h e 872.5, 1346.6 a n d 1377.5 k e V r e s o n a n c e s in t h e ~gF(p, y) r e a c t i o n cross-section.

I0 8

., .

s ..+:.. "" .::.

6 9

4

9

2

:':..:_---

... ~.~.

o

: : " '%"

Ore.b= 146 ~

+."

:.;..,...~--~'.,,..

9

.

9

.

.

.=-

0 9

~C4

E ~2

-?.-'+....',-.,::

9 I9

.

0

=109 ~ 4

. 9

2

.

".'+

.

. ."

,,.,:...-../,....~

... ',.::,...'.....,..

"-':..v....

9

4.....

:

.,

9

.

0

.'.~:'....

4

"

..,,.;.: ,-.:... ".

" ".'."

$

2

O.0

,

1.5

I

2.0 Ea(ivleV)

2',5

3.0

Fig. 2. - Excitation functions for the ~N(d, p)~SN (ground state) reaction at 9l~b = 71% 109% 128~ 146 ~

W e h a v e t e s t e d t h e p r e s e n c e of s i s t e m a t i c errors b y t h e 2 MeV a n g u l a r d i s t r i b u t i o n of t h e elastic s c a t t e r i n g of d e u t e r o n s o n 4~ I n fig. 1 t h e e x c i t a t i o n f u n c t i o n s of t h e elastic s c a t t e r i n g of d e u t e r o n s f r o m 15N are r e p o r t e d , for 0 ~b = 128~ 146~ t h e solid lines are t h e R u t h e r f o r d cross-section. F i g u r e 2, 3 a n d 4 s h o w t h e d i f f e r e n t i a l cross-seotion of t h e 15N(d, p0,1,~,~)l~N r e a c t i o n s .

~0

G. CALVI, ~. CAVAI.LARO, IR. POTENZA, F. R I G G I

and c . 8 P I T A L E R I

Duc to the low Q-value for (d, p) r{~actions ((~o= 0.267 MeV) there is a partial or total overlapping of the proton groups leaving the residual nucleus ~eN in its second and third excitated levels with the deuterons elastically scattered, particularly for O~b< 120~ at O~b----71 ~ 109 ~ it is then impossible, in our experimental conditions, to obtain a separation of d~l, P3 and P216 $ 01

14

12

.:'..

10 9

9"

~

,'%

%

9 ~4

-

9e9

9

9

9

l 9149

i, ~ 9

~..

E

""..3"

b

e ~ b = 146~

:.

9.'.

.

.r

e9 N %

.:".

"! !~-'. :..'. ,..-:::.,.,,~....,~

..

=128 ~

II

9

-....

":'~.. ".:.+

9

=109 o

:""""t""".'"" 9

9

9

9

ao

9

9

.

9

9 .-..

"v'.".-"" "

"," ..,~"..'..:'" 9 ""

"

|

Io

ii~

2o E~(MeV)

21~

3o

F i g . 3. - E x c i t a t i o n f u n c t i o n s f o r ~SN(d. p l ) ~ N * (E* =.0.121 M~V) r e a c t i o n a t 0~ab = 71% 109 ~ 128 ~ I 4 6 ~

EXCITATION FUNCTION8 OF (d, d) ~XD ( d , p )

~P,~c'rtoms ETC.

81

,,-e

% il

g

m 0

9 P+: z l '

~: ["

.',.

?

..?.'

..2" e*

e e

o

,,

u::,

..'",*'" ""

"

~

". +.

II

":

P,

8

~T

!

9

""

9e

m

",*

<:b+

dt+" "

"'-

:"

9

2..":

?:

I~ 9 ee~e

...

..i" 1

.+ 1

I

I

1

I

I

I

0

I

~D

I

C~I

CO

r.

" :..'., .,, +P ~

9 o9

~Z ~176 ~ I

~94-

"ft

o $+~ .~

"ii

~

9

o=,.+4..+

iT .'4

:"

..';"

lie

~

t 9

...s .+8~.

8

"~

4-* o4

I

cO

I

~D

I

.4"

I

c-4 (..J S/qUU )

I

o

I

co

I

s

,+-t

9

I

-q

I

c,~

~

5+~/_Op 4..+ ~2

r,..j

~2

G. CALVI, S. C A V A L L A R 0 , R. POTENZA, F. R I G G I

and c . S P I T A L E R I

The statistical errors for these measurements are of the order of a few per cent; the errors on the absolute value of the cross-sections, both for (d, d) and (d, p) data were cstimatcd to be about 7~o. However at E d < 1.6 MeV thc background/peak ratio increases rapidly, so that background elimination in charged-particle spectra plays an essential role in determining ~he yield of the various proton groups (7). For this rcason we estimated the total error in this energy range ( E d = (1.4--1.6) MeV) to be about 12~ . The bars in fig. 1, 2, 3, 4, however, represent only the statistical crror. As it can be seen from the figures, there is evidence for some resonant structure in the following excitation functions: i) ~SN(d, d)l~N at E d ~ 1.4 MeV corresponding to E*(170) ~ 15.27 MeV; ii) 15N(d,d)lSN, 15N(d, p0)leN (at 01~b= 71~ 15N(d, pl)16N (at 01~b = 128 ~ and 146 ~ and l~N(d, pa)leN at E d _~ 1.8 MeV corresponding to E*(170) 15.62 MeV. This structure can be observed also in the ~SN(d, a)13C (5). iii) 15N(d, p2)16N ~t E a _~ 2.4 MeV, corresponding ~o E*(170)_~ 16.2MeV. This structure is also observed in the 15N(d, n)160 (s). The distance and the widths of these resonances are well ia agreement with the hypothesis of intermediate structure present in the 15N+d reactions in this energy range (9-n).

Thanks are given by the autors to Mr. G. C A R U S O , V. PIPARO and V. SCUD]~RI who operated the V.d.G. accelerator. The work of Dr. P. BO~SI(~NORn, Mr. E. CANGIANO and V. CONNELLI who helped us in making calculations is also gratefully acknowledged.

(7) (") (") (10) (~1)

SL. CAVALLARO, l:t. POTENZ~_ a n d F. RIGGI: R e p o r t I N F N / T C - 7 5 / 6 . 5. L. "~VEIL a n d 1~2. "W. JONES: Phys. Rev., 112, 1975 (1958L A. K . KI~nstAN, L. RODBEttG a n d J . E. YouNG: Phys. Rcv. Left., 11, 422 (1963). A. MEKJI?~N: Adv. Nucl. Phys., 7, 1 (1973). B. BLOCH a n d H . FESIIBACIt: A n n . Phys., 23, 47 (1963).