Chilosi, G.

Cuzzocrea, P.

Morinaga, H.

Ricci, A.

Vingiani, B.

Archive of European Integration

Work done by Istituto Nazionale di Fisica Nucleare 
under the Euratom contract No. 001-60-12 MPAI 
ί^ Τ ί^ίίΙώιίιΪ 
Reprinted from 
IL NUOVO CIMENTO 
Serie X, Voi. 27 - 1963 
Saß 
mi 
Støj 
m 
W m 
m 
%L· 
M> 
This document was prepared under the sponsorship of the Commission of the European - U U U i v , u v r»t*o j i i g j i a i c u UilUCJ. UIC SpOIlSOr 
Atomic Energy Community (EURATOM). 
2° 
r behalf : 
WÄÜß 
^c^u LU me accuracy, 
completeness, or usefulness of the information contained in this document, or t ha t the use 
of any information, appara tus , method, or process disclosed in this document m a y not 
infringe privately owned r ights ; or \ y 
Assume any liability with respect to the use of, or for damages resulting from the use of 
any information, appara tus , method or process disclosed in this document 
rara 
liil»11SIii 
lamini 
SiWflrai 
't?M 
. 
m 
REF 
mi 
U.Í-» 
* · · Ή 
m 
This reprint is intended for restricted distribution only. It reproduces, 
Î
by kind permission of the publisher, an article from -It NUOVO 
CIMENTO", Serie X, Vol. 27 - 1963, 86-92. For further copies please 
apply to II Nuovo Cimento, Via Irnerio, 46 - Bologna, Italia. 
Dieser Sonderdruck ist für eine beschränkte Verteilung bestimmt:.. 
Die Wiedergabe des vorliegenden in „IL NUOVO CIMENTO" 
Serie X, Vol. 27 - 1963, 86-92 erschienen Aufsatzes erfolgt mit 
freundlicher Genehmigung des Herausgebers. Bestellungen weiterer 
Exemplare sind an II Nuovo Cimento, Via Irnerio, 46 - Bologna, Italia, 
Ce tiré à part est exclusivement destiné à une diffusion restreinte. Il 
reprend, avec l'aimable autorisation de l'éditeur, un article publié 
dans « IL NUOVO CIMENTO », Serie X, Vol. 27 - 1963, 86-92. 
Tout autre exemplaire de cet article doit être demandé à lì Nuovo 
Cimento, Via Irnerio, 46 - Bologna, Italia. 
Questo estratto è destinato esclusivamente ad una diffusione limitata. 
Esso è stato riprodotto, per gentile concessione dell'Editore da « Il 
NUOVO CIMENTO », Serie X, Voi. 27 - 1963, 86-92. Ulteriori 
copie dell'articolo debbono essere richieste a II Nuovo Cimento Via 
Irnerio, 46 - Bologna, Italia. 
Deze overdruk is slechts voor beperkte verspreiding bestemd. Het artikel 
is met welwillende toestemming van de uitgever overgenomen uit 
„IL NUOVO CIMENTO", Serie X, Vol. 27 - 1963, 86-92. Meer 
exemplaren kunnen besteld worden bij II Nuovo Cimento, Via Irne-
m m 
rio,. 46 - Bologna, Italia. 
EUR 2 4 4 .e 
REPRINT 
LOWER EXCITED STATES OF 22Ti2S by _ G. CHILOSI Ρ CUZZO CREA (Istituto di Fisica Superiore dell'Università ­ napoli) Η MORINAGA 
(Department of Physics, University of Tokyo), R. A. RICCI, G. B. VIN­
GIAKI (Istituto di Fisica Superiore dell'Università ­ Napoli). 
Work done by Istituto Nazionale di Fisica Nucleare ­ Sotttosezione di Napoli, 
under the Euratom contract No. 001­60­12 MPAI 
Reprinted from "Il Nuovo Cimento", Serie X, Voi. 2/ ­ 1963, pages 86­92. 
A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken by scintillation techniques. B»Sc has been produced by (n, p) reactions with 14 MeV neutrons on metallic titanium foils. The level structure of the two­/ , / , moton configuration in 50Ti has been well established with the following sequence: 0 (0+); 1570 keV (2+); 2 695 (4+) ; 3 215 (6+) A complete decay scheme of ÕOSc is proposed, with ß­transitions to the 6+ and 4+ states in »»Tl. On this basis it is assumed that the spin of the 50Sc ground state is 5+ as expected by the shell model; however the ß­transition probabilities can be explained assuming a configuration mixing between (ƒ,/„) (pj2) and (/,/2) (/5/2) couplings. 
EUR 2 4 4 . e 
REPRINT 
LOWER EXCITED STATES OF l»Ti23 by G. CHILOSI P. CUZZO-
CREA (Istituto di Fisica Superiore dell'Università - Napoli), H. MORINAGA 
(Department of Physics, University of Tokyo), R. A. RICCI, G. B. VIN-
GIANI (Istituto di Fisica Superiore dell'Università - Napoli). 
Work done by Istituto Nazionale di Fisica Nucleare - Sotttosezione di Napoli, 
under the Euratom contract No. 001-60-12 MPAI. 
Reprinted from "Il Nuovo Cimento", Serie X, Voi. 27 - 1963, pages 86-92. 
A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken 
by scintillation techniques. 50Sc has been produced by (n, p) reactions with 
14 MeV neutrons on metallic titanium foils. The level structure of the two-/7/2 
proton configuration in 50Ti has been well established with the following 
sequence: 0 (0+); 1570 keV (2+); 2 695 (4+) ; 3 215 (6+). A complete decay 
scheme of 50Sc is proposed, with ß-transitions to the 6+ and 4+ states in oUTi. 
On this basis it is assumed that the spin of the 50Sc ground state is 5+ as expected 
by the shell model; however the ß-transition probabilities can be explained 
assuming a configuration mixing between (/7/2) (p3l2) and (ƒ,/,,) (/5/2) couplings. 
EUR 2 4 4 . e 
REPRINT 
LOWER EXCITED STATES OF |?,Ti28 by G. CHILOSI, P. CUZZO-
CREA (Istituto di Fisica Superiore dell'Università - Napoli), H. MORINAGA 
(Department of Physics, University of Tokyo), R. A. RICCI, G. B. VIN-
GIANI (Istituto di Fisica Superiore dell'Università - Napoli). 
Work done by Istituto Nazionale di Fisica Nucleare - Sotttosezione di Napoli, 
under the Euratom contract No. 001-60-12 MPAI. 
Reprinted from "Il Nuovo Cimento", Serie X, Voi. 27 - 1963, pages 86-92. 
A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken 
by scintillation techniques. 50Sc has been produced by (n, p) reactions with 
14 MeV neutrons on metallic titanium foils. The level structure of the two-/7/2 
proton configuration in 50Ti has been well established with the following 
sequence: 0 (0+); 1570 keV (2+); 2 695 (4+); 3 215 (6+). A complete decay 
scheme of 50Sc is proposed, with ß-transitions to the 6+ and 4+ states m a0Ti. 
On this basis it is assumed that the spin of the 50Sc ground state is 5+ as expected 
by the shell model; however the ß-transition probabilities can be explained 
assuming a configuration mixing between f/,/2) (p3!2) and (/,/2) (;5/2) couplings. 

G. CHILOSI, et al. 
1° Gennaio 1963 
Il Nuovo Cimento 
Serie X, Vol. 27, pag. 86­92 
Lower Excited States of 25°Ti28 (*). 
G. CHILOSI, P. CUZZOCREA, G. B. VINGIANI, R. A. RICCI and H. MORLNAGA (**) 
Istituto Nazionale di Fisica Nucleare - Sottosezione di Napoli 
Istituto di Fisica Superiore dell' Università ­ Napoli 
(ricevuto Γ8 Giugno 1962) 
Summary. — A detailed investigation of the decay of 50Sc (1.7 min) has 
been undertaken by scintillation techniques. 50Sc has been produced 
by (n, p) reactions with 14 MeV neutrons on metallic t i tanium foils. 
The level structure of the two­/j proton configuration in 50Ti has been 
well established with the following sequence: 0 (0+); 1570keV (2+); 
2 695 (4+); 3 215 (6+). A complete decay scheme of 50Sc is proposed, 
with ß­transitions to the 6+ and 4+ states in 50Ti. On this basis it is 
assumed tha t the spia of the 60Sc ground state is 5+ as expected by the 
shell model; however the ß­transition probabilities can be explained 
assuming a configuration mixing between (fi)(p%) and (ƒ})(ƒ$) couplings. 
1. - Introduction. 
Two identical particles with total angular momentum j in a doubly magic 
core gives a sequence of levels 0, 2, 4 ... (2j — 1). A detailed knowledge of 
such sequence is important to understand the forces to be used in shell 
model calculations C-). 
There are, however, only a few cases where this sequence is well known. 
One specifically interesting case is that of two l/¿ nucléons since this is a single 
j shell and both (v/*)2 (neutrons) and (π/4)2 (protons) configurations are acces-
(*) Work performed under a contract between EURATOM and C.N.E.N. 
(") Permanent address: Department of Physics, University of Tokyo. 
i1) C. LEVINSON and K. W. F O R D : Phys. Bev., 100, 13 (1955); R. D. LAWSON 
and J . L . U R E T K S K Y : Phys. Bev., 106, 1369 (1957); I . TALMI : Proc. Behovoth Oonf. 
Nucl. Struct. 1957, (1958), pp . 31-45; Phys. Bev., 126, 1096 (1962); I. TALMI and 
I. U N N A : Ann. Bev. Nucl. Sci., 10, 353 (1960). 
2 LOWER EXCITED STATES OF 2 2 Ti 2 8 [87] 
sible experimentally. The cases in point are 42,Ca22 and f2Ti28 respectively, 
both with doubly magic, although different, core. 
Recently a high-spin isomer of 42Sc was found to decay to a high-spin state 
of 42Ca which apparently cascades through the above mentioned sequence (2). 
The situation seems to be quite similar to t h a t of 5°Ti (3); however some 
doubt in the level assignement of 5°Ti (4) did not permit a conclusive com­
parison. 
In order to know the level sequence of 50Ti more precisely, we tried to 
investigate the decay of 50Sc very carefully. 
2. - Measurements and results. 
Titanium metallic foils (99.9% purity) were bombarded with 14 MeV 
neutrons of the ΑΪΓ 400 accelerator for ~ 2 min, and the activity was meas­
ured no more than 30 s after the end of the irradiation. The γ-ray activity 
was measured with the conventional γ scintillation spectrometer of our labo­
ra tory (75 m m x 75 m m well type Nal(Tl) crystal coupled to a 6363 DuMont 
photomultiplier and connected to a 200 channel L A B E N analyser). 
The ß­ray activity was measured with a scintillation spectrometer con­
sisting of an antracene crystal (30 m m diameter, 25 m m height) calibrated 
with the end point energies of the β" spectra of i eO (4.6 MeV) and 28A1 
(2.87 MeV), in the same condition of geometry and backing. 
The half life was followed, in every case, for a t least 30 min; the result 
found: (1.7 ± 0.1) min, is in good agreement with t ha t previously reported (4). 
The long­lived activities produced, i.e. 45Ti (Tè = 3.1 hours) and 48Sc 
( ¡ p _ l , 8 days) were well recognized and the relative contribution taken into 
account. For the ß­ray spectrum this contribution was expected, and indeed 
found, to be unimpor tan t for energies larger t han 1 MeV. 
Figure 1 displays the γ scintillation spectrum taken shortly after the irra­
diation and the corresponding one taken 30 min later. Three γ­rays with 
energies 520, 1125 and 1570 keV were clearly identified in the short­lived 
activity, whereas the pulse height distribution due to the long­lived par t check 
very well with t ha t expected for 45Ti and 48Sc. 
(2) J . W . N E L S O N , H . S. P L E N D L a n d J . D . O B E R H O L T Z E R : Proc. of the Butherford 
Jubilee Int. Conj. Manchester 1961; Bull. Am. Phys. Soe., 7, 286 (19G2); P . C. R O G E R S 
a n d G. E . G O R D O N : M . I . T . L a b . N u c l . Sci . P r o g r e s s R e p o r t , M a y 1, 12 (1962) . 
(3) H . M O R I N A G A , N . M U T S U R O a n d M . S U G A W A R A : Phys. Bev., 114 , 1146 (1959) . 
(4) H . M O R I N A G A a n d P . B L E U L E R : Phys. Bev., 100 , 1236 (1955) ; H . M O R I N A G A : 
U . S . A E C R e p o r t C O O ­ 1 7 3 (1956) , p . 3 7 . 
[88] G. CHILOSI , P . CUZZOCREA, G. B . VINGIANI , R . A . RICCI a n d H . MORINAGA 3 
An accurate determination of the energy of the 520 keV γ­ray, which could 
have been confused with annihilation radiations, was undertaken in the fol­
lowing way: the low energy spectrum of 50Sc was detected in the presence of 
the 278 keV and 662 keV γ­radiations of 203Hg and 137Cs sources ; the same 
measurement was performed with a 22Nfa source in the place of >°Sc. The 
different position of the 50Sc γ­ray and of the 511 keV annihilation peak of 
22ÎJ"a was checked against the 2°3Hg and 137Cs γ­radiation. 
residual _sum m ing 
20 25 30 35 40 45 50 60 70 80 90 100 
channel number 
F i g . 1. 
This can also be seen in Fig. 1 where the position of the 520 keV γ­ray of 
50Sc can be compared with that of the annihilation peak of the long­lived 
45Ti after the first one has disappeared. We were able, in this way, to give 
an energy value of (520 ± 3) keV. The coincidence relationships were deter­
mined by the scintillation technique, which, in this case, was of special use­
fulness. 
This is shown in Fig. 2 where the summing spectrum taken with the source 
in the well of the Nal(Tl) crystal is reported ; the contribution of the long­lived 
activities is also shown in the lower part of the figure. The presence of sum­
LOWER EXCITED STATES OF ΙΐΎΐχ [89] 
ruing peaks at 3230, 2 700, 2100 and 1640 keV is clearly evident and has 
been interpreted as due to the triple cascade 520-1125-1570 keV. 
30 40 50 
channel number 
Fig. 2. 
The results on γ-rays and γ-γ coincidences are summarized in Table I, 
where the relative intensities found by analysing the scintillation spectrum in 
TABLE I. 
γ-rays from the decay of 50Sc 
(Th= (1.7 + 0.1) min) 
Energy (keV) 
520 ± 3 
1125+10 
1570+10 
Intensity (%) 
85 + 7 
100 + 8 
100 
Summing peaks from 50Sc 
Energy (keV) 
1040+15 
2 100+10 
2 700+10 
3230 + 20 
Interpretation 
520-1-1125 
520+ 1 570 
1125+1570 
520+1125+1570 
[90] G. CHILOSI, P. CUZZOCREA, G. B. VINOJANI, R. A. RICCI a n d H. MORINAGA 5 
NP 
fE 
2.5 
2 
1.5 
1 
0.5 
0 . 3 -
0 
ί (3 .3*0 .2) 
I V ._ 
2 3 
energy M e V 
Fig. 3. 
1.7min 2 l 5 c ? 9 
-3 .3 ; 8 5 7 
log ί ί =5.2 ; 
- 3 . 8 , 1 5 ° / 
/o 
log ff =6.2 ' 
0' 
50 
22*ΙΊ28 
- 3 215 
2 695 
1 5 70 
Fig. 4. 
6+-
4 f -
2 + -
0+-
2+ 
3 191 
2 752 
2422 
— 1 836 
1 524 
42 
2oCa¿; 
6 . LOWER EXCITED STATES OF 2?Ti28 [ 9 l ] 
the usual way (s), are reported. They are consistent with an upper level a t 
3 215 keV which decays to the ground s ta te via the triple cascade 520­1125­
1570 keV γ­ray producing intermediate levels a t 2 695 a n d l 5 7 0 k e V . The 
Fermi­Kurie plot of the ß­ray spectrum is reported in Fig. 3. An end point 
energy of (3.4 ± 0.2) MeV was found, which was interpreted as mostly due to 
the lower energy branch i.e. the β transit ion to the 3 215 keV level. Taking 
into account the relative population of the 2 695 keV level as given by the γ­ray 
intensity balance (85 % ) , our results are consistent with the assumption of two 
β branches of energies (3.3 + 0.1) MeV (85%) and ( 3 . 8 + 0 . 2 ) MeV (15%) res­
pectively. The decay scheme which can be proposed is shown in Fig. 4, where 
the level s t ructure of 5°Ti is compared with the situation reported for 42Ca. 
3. ­ Discussion. 
The level sequence of 50Ti supports very well the expected situation on 
the basis of the (jt/¡)2 coupling scheme. The correspondence with the level 
sequence of 42Ca ((vfz)2 configuration) is really impressive. The 1 836 keV (0+) 
and the 2 422 keV (2+) levels in 42Ca may be understood as due to core 
excitations (3). 
The similarities of the two­particle spectra in both cases show the validity 
of the j-j description; it is in fact expected on the basis of such a coupling 
scheme (4) t h a t the levels with seniority S=2 (namely the 2 + , 4+ and 6+ levels) 
would occur at the same energies and tha t the distance between two successive 
levels of the (j)2 configuration decreases with increasing spin. 
This is also supported for instance by the level sequence in ÜIMO50, where 
the (π#|)2 coupling scheme seems to apply (c). 
Another interesting remark can be made in connection with the decay of 50Sc. 
The relative population of the 6+ and 4+ levels in 50Ti suggests a spin 5+ 
for the 50Sc ground­state ; this is also expected by shell model considerations 
for a (fi){pi) configuration. This configuration would correspond to a slowing 
down of the ß­decay, because a pt ­> /j transit ion is Z­forbidden, assuming 
tha t both 4+ and 6+ states in 50Ti come from (/j)2 pure configuration. This 
fact is in good agreement with the high experimental log/i values for the 
ß­decay (5.2 and 6.2 respectively). 
Among the possible admixtures to the 5 + ground s ta te of 50Sc the nearest 
one which can give rise to ß­decay to the (/j)2 configuration is (fi){fi)· I f 
we assume tha t this admixture is responsible for the ß­decay we may t ry to 
(5) S e e f o r i n s t a n c e R . A . R I C C I , G . C H I L O S I , G . V A R C A C C I O , G . Β . V I N G I A N I a n d 
R . V A N L I E S H O U T : NUOVO Cimento, 1 7 , 5 2 3 ( 1 9 6 0 ) . 
(6) R . V A N L I E S H O U T , S . M O N A R O , G . B . V I N G I A N I a n d H . M O R I N A G A : B u l l . A m . 
Phys. Soc, 7 , 3 4 2 ( 1 9 6 2 ) . 
[92] G. CHILOSI, P. CUZZOCREA, G. B. VINGIANI, R. A. RICCI a n d H. MORINAGA 7 
calculate the ratio of the log ft values of the transition to the 6+ and 4+ states 
as follows. 
We assume that the states be describable according to the shell model, 
with no residual interaction. If the initial state is [(πΐ,^νΐ^)]^ the Gamow-
Teller amplitudes for the decay [Μ,ΚνΖ,-ι)]/, ^ [(πΖ,)2],, are: 
M? ={-!) /f+l (2j —l)(2j + l)(2i1 + l) 
1 
ζ,ΙΙψΜ^Ι,Μ,} W(j 7 - 1 7 , 1 , ; lj) 
where Z,, Z, are the total angular momentum of the initial and final states 
with components JZ, and Mt; W the Racah coefficient. 
The transition probability is then proportional to 
| M a T | 2 s ¿ Jfjwjrçr = (27­D(2j + l)(2Z1 + l) ^ . _ l j r j _ 
­ 1 J 
In particular for 50Sc we assume that the initial state is [(π/})(ν/|)]., 5 and we 
use the above formulae with ƒ = ! , Z¡ = 5 and Z, = 4 and 6 for 50Ti. 
We find in this way for the ratio of the transition probabilities at the 
states lt = 4 and Z, = 6 the following result: 
(/0*-4/(/0β->. = ~ 
Δ 
which yields: 
log (/i)5^4 ­ log (/«)„_ = 1.24 . 
This is in good agreement with the experimental observation. 
* * * 
We would like to express our thanks to Professor G. COBTINI for his inte­
rest in this work, to Prof. A. H. WAPSTRA and M. JEAN for interesting stimu­
lating discussions. 
The kind interest of Prof. P. C. GUGELOT is also gratefully acknowledged. 
R I A S S U N T O 
Si è s tudiata la sequenza di livelli del 50Ti (configurazione protónica (/¡)2) t ramite 
il decadimento del 50Sc (1.7 min) prodotto per reazione (n, p) su titanio" metallico. 
Gli spettri β e γ sono stati determinati con tecniche a scintillazione: t re raggi γ in 
cascata sono stat i chiaramente messi in evidenza con energia (520 + 3), (1125+10) e 
(1570+10) KeV corrispondenti alla sequenza di livelli: 0 (0+), 1570 (2+), 2 695 (4+) 
e 3 215 (6+) nel 50Ti. Lo spettro β è consistente con l'esistenza di 2 rami di energia 3.3 
e 3.8 MeV che popolano i livelli 6+ e 4+ del 50Ti. Si assegna uno spin 5+ allo stato 
fondamentale del 50Sc, che probabilmente corrisponde ad una miscela di configurazioni 
(/i)(i»|) e (/})(/|). Lo schema di livelli del 50Ti è confrontato con quello del 42Ca. 
G. CHILOSI, et al. 
10 Gennaio 1963 
11 Nuovo Cimento 
Serie X, Vol. 27, pag. 86-92 




LOWER EXCITED STATES OF 50 22TI28. EUR 244.e

Work done by Istituto Nazionale di Fisica Nucleare under the Euratom contract No. 001-60-12 MPAI ί^ Τ ί^ίίΙώιίιΪ Reprinted from IL NUOVO CIMENTO Serie X, Voi. 27 - 1963 Saß mi Støj m W m m %L· M> This document was prepared under the sponsorship of the Commission of the European - U U U i v , u v r»t*o j i i g j i a i c u UilUCJ. UIC SpOIlSOr Atomic Energy Community (EURATOM). 2° r behalf : WÄÜß ^c^u LU me accuracy, completeness, or usefulness of the information contained in this document, or t ha t the use of any information, appara tus , method, or process disclosed in this document m a y not infringe privately owned r ights ; or \ y Assume any liability with respect to the use of, or for damages resulting from the use of any information, appara tus , method or process disclosed in this document rara liil»11SIii lamini SiWflrai 't?M . m REF mi U.Í-» * · · Ή m This reprint is intended for restricted distribution only. It reproduces, Îby kind permission of the publisher, an article from -It NUOVO CIMENTO", Serie X, Vol. 27 - 1963, 86-92. For further copies please apply to II Nuovo Cimento, Via Irnerio, 46 - Bologna, Italia. Dieser Sonderdruck ist für eine beschränkte Verteilung bestimmt:.. Die Wiedergabe des vorliegenden in „IL NUOVO CIMENTO" Serie X, Vol. 27 - 1963, 86-92 erschienen Aufsatzes erfolgt mit freundlicher Genehmigung des Herausgebers. Bestellungen weiterer Exemplare sind an II Nuovo Cimento, Via Irnerio, 46 - Bologna, Italia, Ce tiré à part est exclusivement destiné à une diffusion restreinte. Il reprend, avec l'aimable autorisation de l'éditeur, un article publié dans « IL NUOVO CIMENTO », Serie X, Vol. 27 - 1963, 86-92. Tout autre exemplaire de cet article doit être demandé à lì Nuovo Cimento, Via Irnerio, 46 - Bologna, Italia. Questo estratto è destinato esclusivamente ad una diffusione limitata. Esso è stato riprodotto, per gentile concessione dell'Editore da « Il NUOVO CIMENTO », Serie X, Voi. 27 - 1963, 86-92. Ulteriori copie dell'articolo debbono essere richieste a II Nuovo Cimento Via Irnerio, 46 - Bologna, Italia. Deze overdruk is slechts voor beperkte verspreiding bestemd. Het artikel is met welwillende toestemming van de uitgever overgenomen uit „IL NUOVO CIMENTO", Serie X, Vol. 27 - 1963, 86-92. Meer exemplaren kunnen besteld worden bij II Nuovo Cimento, Via Irne-m m rio,. 46 - Bologna, Italia. EUR 2 4 4 .e REPRINT LOWER EXCITED STATES OF 22Ti2S by _ G. CHILOSI Ρ CUZZO CREA (Istituto di Fisica Superiore dell'Università ­ napoli) Η MORINAGA (Department of Physics, University of Tokyo), R. A. RICCI, G. B. VIN­GIAKI (Istituto di Fisica Superiore dell'Università ­ Napoli). Work done by Istituto Nazionale di Fisica Nucleare ­ Sotttosezione di Napoli, under the Euratom contract No. 001­60­12 MPAI Reprinted from "Il Nuovo Cimento", Serie X, Voi. 2/ ­ 1963, pages 86­92. A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken by scintillation techniques. B»Sc has been produced by (n, p) reactions with 14 MeV neutrons on metallic titanium foils. The level structure of the two­/ , / , moton configuration in 50Ti has been well established with the following sequence: 0 (0+); 1570 keV (2+); 2 695 (4+) ; 3 215 (6+) A complete decay scheme of ÕOSc is proposed, with ß­transitions to the 6+ and 4+ states in »»Tl. On this basis it is assumed that the spin of the 50Sc ground state is 5+ as expected by the shell model; however the ß­transition probabilities can be explained assuming a configuration mixing between (ƒ,/„) (pj2) and (/,/2) (/5/2) couplings. EUR 2 4 4 . e REPRINT LOWER EXCITED STATES OF l»Ti23 by G. CHILOSI P. CUZZO-CREA (Istituto di Fisica Superiore dell'Università - Napoli), H. MORINAGA (Department of Physics, University of Tokyo), R. A. RICCI, G. B. VIN-GIANI (Istituto di Fisica Superiore dell'Università - Napoli). Work done by Istituto Nazionale di Fisica Nucleare - Sotttosezione di Napoli, under the Euratom contract No. 001-60-12 MPAI. Reprinted from "Il Nuovo Cimento", Serie X, Voi. 27 - 1963, pages 86-92. A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken by scintillation techniques. 50Sc has been produced by (n, p) reactions with 14 MeV neutrons on metallic titanium foils. The level structure of the two-/7/2 proton configuration in 50Ti has been well established with the following sequence: 0 (0+); 1570 keV (2+); 2 695 (4+) ; 3 215 (6+). A complete decay scheme of 50Sc is proposed, with ß-transitions to the 6+ and 4+ states in oUTi. On this basis it is assumed that the spin of the 50Sc ground state is 5+ as expected by the shell model; however the ß-transition probabilities can be explained assuming a configuration mixing between (/7/2) (p3l2) and (ƒ,/,,) (/5/2) couplings. EUR 2 4 4 . e REPRINT LOWER EXCITED STATES OF |?,Ti28 by G. CHILOSI, P. CUZZO-CREA (Istituto di Fisica Superiore dell'Università - Napoli), H. MORINAGA (Department of Physics, University of Tokyo), R. A. RICCI, G. B. VIN-GIANI (Istituto di Fisica Superiore dell'Università - Napoli). Work done by Istituto Nazionale di Fisica Nucleare - Sotttosezione di Napoli, under the Euratom contract No. 001-60-12 MPAI. Reprinted from "Il Nuovo Cimento", Serie X, Voi. 27 - 1963, pages 86-92. A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken by scintillation techniques. 50Sc has been produced by (n, p) reactions with 14 MeV neutrons on metallic titanium foils. The level structure of the two-/7/2 proton configuration in 50Ti has been well established with the following sequence: 0 (0+); 1570 keV (2+); 2 695 (4+); 3 215 (6+). A complete decay scheme of 50Sc is proposed, with ß-transitions to the 6+ and 4+ states m a0Ti. On this basis it is assumed that the spin of the 50Sc ground state is 5+ as expected by the shell model; however the ß-transition probabilities can be explained assuming a configuration mixing between f/,/2) (p3!2) and (/,/2) (;5/2) couplings. G. CHILOSI, et al. 1° Gennaio 1963 Il Nuovo Cimento Serie X, Vol. 27, pag. 86­92 Lower Excited States of 25°Ti28 (*). G. CHILOSI, P. CUZZOCREA, G. B. VINGIANI, R. A. RICCI and H. MORLNAGA (**) Istituto Nazionale di Fisica Nucleare - Sottosezione di Napoli Istituto di Fisica Superiore dell' Università ­ Napoli (ricevuto Γ8 Giugno 1962) Summary. — A detailed investigation of the decay of 50Sc (1.7 min) has been undertaken by scintillation techniques. 50Sc has been produced by (n, p) reactions with 14 MeV neutrons on metallic t i tanium foils. The level structure of the two­/j proton configuration in 50Ti has been well established with the following sequence: 0 (0+); 1570keV (2+); 2 695 (4+); 3 215 (6+). A complete decay scheme of 50Sc is proposed, with ß­transitions to the 6+ and 4+ states in 50Ti. On this basis it is assumed tha t the spia of the 60Sc ground state is 5+ as expected by the shell model; however the ß­transition probabilities can be explained assuming a configuration mixing between (fi)(p%) and (ƒ})(ƒ$) couplings. 1. - Introduction. Two identical particles with total angular momentum j in a doubly magic core gives a sequence of levels 0, 2, 4 ... (2j — 1). A detailed knowledge of such sequence is important to understand the forces to be used in shell model calculations C-). There are, however, only a few cases where this sequence is well known. One specifically interesting case is that of two l/¿ nucléons since this is a single j shell and both (v/*)2 (neutrons) and (π/4)2 (protons) configurations are acces-(*) Work performed under a contract between EURATOM and C.N.E.N. (") Permanent address: Department of Physics, University of Tokyo. i1) C. LEVINSON and K. W. F O R D : Phys. Bev., 100, 13 (1955); R. D. LAWSON and J . L . U R E T K S K Y : Phys. Bev., 106, 1369 (1957); I . TALMI : Proc. Behovoth Oonf. Nucl. Struct. 1957, (1958), pp . 31-45; Phys. Bev., 126, 1096 (1962); I. TALMI and I. U N N A : Ann. Bev. Nucl. Sci., 10, 353 (1960). 2 LOWER EXCITED STATES OF 2 2 Ti 2 8 [87] sible experimentally. The cases in point are 42,Ca22 and f2Ti28 respectively, both with doubly magic, although different, core. Recently a high-spin isomer of 42Sc was found to decay to a high-spin state of 42Ca which apparently cascades through the above mentioned sequence (2). The situation seems to be quite similar to t h a t of 5°Ti (3); however some doubt in the level assignement of 5°Ti (4) did not permit a conclusive com­parison. In order to know the level sequence of 50Ti more precisely, we tried to investigate the decay of 50Sc very carefully. 2. - Measurements and results. Titanium metallic foils (99.9% purity) were bombarded with 14 MeV neutrons of the ΑΪΓ 400 accelerator for ~ 2 min, and the activity was meas­ured no more than 30 s after the end of the irradiation. The γ-ray activity was measured with the conventional γ scintillation spectrometer of our labo­ra tory (75 m m x 75 m m well type Nal(Tl) crystal coupled to a 6363 DuMont photomultiplier and connected to a 200 channel L A B E N analyser). The ß­ray activity was measured with a scintillation spectrometer con­sisting of an antracene crystal (30 m m diameter, 25 m m height) calibrated with the end point energies of the β" spectra of i eO (4.6 MeV) and 28A1 (2.87 MeV), in the same condition of geometry and backing. The half life was followed, in every case, for a t least 30 min; the result found: (1.7 ± 0.1) min, is in good agreement with t ha t previously reported (4). The long­lived activities produced, i.e. 45Ti (Tè = 3.1 hours) and 48Sc ( ¡ p _ l , 8 days) were well recognized and the relative contribution taken into account. For the ß­ray spectrum this contribution was expected, and indeed found, to be unimpor tan t for energies larger t han 1 MeV. Figure 1 displays the γ scintillation spectrum taken shortly after the irra­diation and the corresponding one taken 30 min later. Three γ­rays with energies 520, 1125 and 1570 keV were clearly identified in the short­lived activity, whereas the pulse height distribution due to the long­lived par t check very well with t ha t expected for 45Ti and 48Sc. (2) J . W . N E L S O N , H . S. P L E N D L a n d J . D . O B E R H O L T Z E R : Proc. of the Butherford Jubilee Int. Conj. Manchester 1961; Bull. Am. Phys. Soe., 7, 286 (19G2); P . C. R O G E R S a n d G. E . G O R D O N : M . I . T . L a b . N u c l . Sci . P r o g r e s s R e p o r t , M a y 1, 12 (1962) . (3) H . M O R I N A G A , N . M U T S U R O a n d M . S U G A W A R A : Phys. Bev., 114 , 1146 (1959) . (4) H . M O R I N A G A a n d P . B L E U L E R : Phys. Bev., 100 , 1236 (1955) ; H . M O R I N A G A : U . S . A E C R e p o r t C O O ­ 1 7 3 (1956) , p . 3 7 . [88] G. CHILOSI , P . CUZZOCREA, G. B . VINGIANI , R . A . RICCI a n d H . MORINAGA 3 An accurate determination of the energy of the 520 keV γ­ray, which could have been confused with annihilation radiations, was undertaken in the fol­lowing way: the low energy spectrum of 50Sc was detected in the presence of the 278 keV and 662 keV γ­radiations of 203Hg and 137Cs sources ; the same measurement was performed with a 22Nfa source in the place of >°Sc. The different position of the 50Sc γ­ray and of the 511 keV annihilation peak of 22ÎJ"a was checked against the 2°3Hg and 137Cs γ­radiation. residual _sum m ing 20 25 30 35 40 45 50 60 70 80 90 100 channel number F i g . 1. This can also be seen in Fig. 1 where the position of the 520 keV γ­ray of 50Sc can be compared with that of the annihilation peak of the long­lived 45Ti after the first one has disappeared. We were able, in this way, to give an energy value of (520 ± 3) keV. The coincidence relationships were deter­mined by the scintillation technique, which, in this case, was of special use­fulness. This is shown in Fig. 2 where the summing spectrum taken with the source in the well of the Nal(Tl) crystal is reported ; the contribution of the long­lived activities is also shown in the lower part of the figure. The presence of sum­LOWER EXCITED STATES OF ΙΐΎΐχ [89] ruing peaks at 3230, 2 700, 2100 and 1640 keV is clearly evident and has been interpreted as due to the triple cascade 520-1125-1570 keV. 30 40 50 channel number Fig. 2. The results on γ-rays and γ-γ coincidences are summarized in Table I, where the relative intensities found by analysing the scintillation spectrum in TABLE I. γ-rays from the decay of 50Sc (Th= (1.7 + 0.1) min) Energy (keV) 520 ± 3 1125+10 1570+10 Intensity (%) 85 + 7 100 + 8 100 Summing peaks from 50Sc Energy (keV) 1040+15 2 100+10 2 700+10 3230 + 20 Interpretation 520-1-1125 520+ 1 570 1125+1570 520+1125+1570 [90] G. CHILOSI, P. CUZZOCREA, G. B. VINOJANI, R. A. RICCI a n d H. MORINAGA 5 NP fE 2.5 2 1.5 1 0.5 0 . 3 -0 ί (3 .3*0 .2) I V ._ 2 3 energy M e V Fig. 3. 1.7min 2 l 5 c ? 9 -3 .3 ; 8 5 7 log ί ί =5.2 ; - 3 . 8 , 1 5 ° / /o log ff =6.2 ' 0' 50 22*ΙΊ28 - 3 215 2 695 1 5 70 Fig. 4. 6+-4 f -2 + -0+-2+ 3 191 2 752 2422 — 1 836 1 524 42 2oCa¿; 6 . LOWER EXCITED STATES OF 2?Ti28 [ 9 l ] the usual way (s), are reported. They are consistent with an upper level a t 3 215 keV which decays to the ground s ta te via the triple cascade 520­1125­1570 keV γ­ray producing intermediate levels a t 2 695 a n d l 5 7 0 k e V . The Fermi­Kurie plot of the ß­ray spectrum is reported in Fig. 3. An end point energy of (3.4 ± 0.2) MeV was found, which was interpreted as mostly due to the lower energy branch i.e. the β transit ion to the 3 215 keV level. Taking into account the relative population of the 2 695 keV level as given by the γ­ray intensity balance (85 % ) , our results are consistent with the assumption of two β branches of energies (3.3 + 0.1) MeV (85%) and ( 3 . 8 + 0 . 2 ) MeV (15%) res­pectively. The decay scheme which can be proposed is shown in Fig. 4, where the level s t ructure of 5°Ti is compared with the situation reported for 42Ca. 3. ­ Discussion. The level sequence of 50Ti supports very well the expected situation on the basis of the (jt/¡)2 coupling scheme. The correspondence with the level sequence of 42Ca ((vfz)2 configuration) is really impressive. The 1 836 keV (0+) and the 2 422 keV (2+) levels in 42Ca may be understood as due to core excitations (3). The similarities of the two­particle spectra in both cases show the validity of the j-j description; it is in fact expected on the basis of such a coupling scheme (4) t h a t the levels with seniority S=2 (namely the 2 + , 4+ and 6+ levels) would occur at the same energies and tha t the distance between two successive levels of the (j)2 configuration decreases with increasing spin. This is also supported for instance by the level sequence in ÜIMO50, where the (π#|)2 coupling scheme seems to apply (c). Another interesting remark can be made in connection with the decay of 50Sc. The relative population of the 6+ and 4+ levels in 50Ti suggests a spin 5+ for the 50Sc ground­state ; this is also expected by shell model considerations for a (fi){pi) configuration. This configuration would correspond to a slowing down of the ß­decay, because a pt ­> /j transit ion is Z­forbidden, assuming tha t both 4+ and 6+ states in 50Ti come from (/j)2 pure configuration. This fact is in good agreement with the high experimental log/i values for the ß­decay (5.2 and 6.2 respectively). Among the possible admixtures to the 5 + ground s ta te of 50Sc the nearest one which can give rise to ß­decay to the (/j)2 configuration is (fi){fi)· I f we assume tha t this admixture is responsible for the ß­decay we may t ry to (5) S e e f o r i n s t a n c e R . A . R I C C I , G . C H I L O S I , G . V A R C A C C I O , G . Β . V I N G I A N I a n d R . V A N L I E S H O U T : NUOVO Cimento, 1 7 , 5 2 3 ( 1 9 6 0 ) . (6) R . V A N L I E S H O U T , S . M O N A R O , G . B . V I N G I A N I a n d H . M O R I N A G A : B u l l . A m . Phys. Soc, 7 , 3 4 2 ( 1 9 6 2 ) . [92] G. CHILOSI, P. CUZZOCREA, G. B. VINGIANI, R. A. RICCI a n d H. MORINAGA 7 calculate the ratio of the log ft values of the transition to the 6+ and 4+ states as follows. We assume that the states be describable according to the shell model, with no residual interaction. If the initial state is [(πΐ,^νΐ^)]^ the Gamow-Teller amplitudes for the decay [Μ,ΚνΖ,-ι)]/, ^ [(πΖ,)2],, are: M? ={-!) /f+l (2j —l)(2j + l)(2i1 + l) 1 ζ,ΙΙψΜ^Ι,Μ,} W(j 7 - 1 7 , 1 , ; lj) where Z,, Z, are the total angular momentum of the initial and final states with components JZ, and Mt; W the Racah coefficient. The transition probability is then proportional to | M a T | 2 s ¿ Jfjwjrçr = (27­D(2j + l)(2Z1 + l) ^ . _ l j r j _ ­ 1 J In particular for 50Sc we assume that the initial state is [(π/})(ν/|)]., 5 and we use the above formulae with ƒ = ! , Z¡ = 5 and Z, = 4 and 6 for 50Ti. We find in this way for the ratio of the transition probabilities at the states lt = 4 and Z, = 6 the following result: (/0*-4/(/0β->. = ~ Δ which yields: log (/i)5^4 ­ log (/«)„_ = 1.24 . This is in good agreement with the experimental observation. * * * We would like to express our thanks to Professor G. COBTINI for his inte­rest in this work, to Prof. A. H. WAPSTRA and M. JEAN for interesting stimu­lating discussions. The kind interest of Prof. P. C. GUGELOT is also gratefully acknowledged. R I A S S U N T O Si è s tudiata la sequenza di livelli del 50Ti (configurazione protónica (/¡)2) t ramite il decadimento del 50Sc (1.7 min) prodotto per reazione (n, p) su titanio" metallico. Gli spettri β e γ sono stati determinati con tecniche a scintillazione: t re raggi γ in cascata sono stat i chiaramente messi in evidenza con energia (520 + 3), (1125+10) e (1570+10) KeV corrispondenti alla sequenza di livelli: 0 (0+), 1570 (2+), 2 695 (4+) e 3 215 (6+) nel 50Ti. Lo spettro β è consistente con l'esistenza di 2 rami di energia 3.3 e 3.8 MeV che popolano i livelli 6+ e 4+ del 50Ti. Si assegna uno spin 5+ allo stato fondamentale del 50Sc, che probabilmente corrisponde ad una miscela di configurazioni (/i)(i»|) e (/})(/|). Lo schema di livelli del 50Ti è confrontato con quello del 42Ca. G. CHILOSI, et al. 10 Gennaio 1963 11 Nuovo Cimento Serie X, Vol. 27, pag. 86-92 

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