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Comparative half-lives of ΔI = 3, no beta transitions, in even nuclei
Nuclear Physics 75 (1966) 79--80; (~) North-Holland Publishing Co., Amsterdam Not to be reproduced by photoprint or microfilm without written permission from the publisher
C O M P A R A T I V E H A L F - L I V E S O F AI = 3, N O B E T A T R A N S I T I O N S , IN EVEN NUCLEI s. M. BRAHMAVAR
Department of Physics, Panjab University, Chandigarh-3, India Received 9 April 1965 Abstract: The quantity log f,3t = log((S3)fot), which takes into account the dependence of the
shape factor S,3 in the integration over the spectrum, is expected to be a better constant for A1 = 3, no beta transitions, than the usualft value. A survey and analysis of all such transitions indicates anomalies for two transitions in ~6A1. I n recent years there have b e e n m a d e m a n y systematic studies of comparative halflives of various allowed beta transitions to even nuclei. O f these, the study 1) of allowed beta transitions from 1 +, 2 ÷ a n d 3 ÷ p a r e n t beta emitters has s h o w n h i n d r a n c e in all these transitions. A similar study 2) has m a d e it possible to propose a n empirical relation c o n n e c t i n g the energy ratios a n d the log f t values of beta transitions to v i b r a t i o n a l levels o f even nuclei. These studies i n n u c l e a r systematics have been useful i n u n d e r s t a n d i n g the basic n a t u r e of various beta transitions a n d the properties of low-lying excited states of even nuclei. A survey o f allowed a n d f o r b i d d e n beta transitions indicates that there is a small g r o u p o f beta transitions n a m e l y the u n i q u e second f o r b i d d e n A I = 3, n o transition, a b o u t which theory has something definite to say. Basically the q u a n t i t y TABLE 1
Comparative half-lives for AI = 3, no beta transitions Parent nucleus
Daughter nucleus
Type of transition
Energy of transition (MeV)
Comparative half-life
Ref.
1°Be
1°B
0+ ~ 3+
0.555
12.07
~, b)
2~Na
~2Ne
3+ --->0+
1.830
11.9
a. b)
~°A1
~6Mg
5+ ~ 2+ 5+ ~ 2+'
1.16 1.04
14.2 12.9
b) b)
e°Co
e°Ni
5+ --->2+
1.48
11.8
~)
a) D. C. Camp, L. M. Langer and D. R. Smith, Phys. Rev. 123 (1961) 241 b) Landolt-Bornstein: Energy levels of nuclei A = 5 to A ~ 257 (Springer-Verlag, 1961) Present address: Department of Physics and Astronomy Vanderbilt University, Nashville, Tennessee, USA. 79
80
S
M, BRAHMAVAR
log f 3 t = log ( ( S 3 ) f o t), which takes into account the dependence of the shape factor $23 in the integration over the spectrum, is expected to be a better constant for AI = 3, no beta transitions. Thus, an attempt has been made in this note to see how far this theoretical expectation is valid in such transitions. The data on A I = 3, no transitions, collected from various publications are presented in table 1, the columns o f which are selfexplanatory. Although the expected constancy is followed by three comparative half-lives, the anomalies for two transitions in 26A1 are quite surprising. Thus one is led to enquire into the large value of log f t for two such transitions in 26AI and test the validity of these as A1 = 3, no transitions. The experimental work of Jastram et al. 3) is not inconsistent with the 5 + ~ 2 + transition as a A1 -- 3, no interpretation obtained from spectral shape measurements 4)., Moreover this particular nucleus (26Mg) is expected t o lie in a region of transition toward a vibrational type o f spectrum and has exhibited interesting characteristics as regards the first excited state 5) and other low-lying states. It is deemed to be quite fruitful to put this nucleus to a precise experimental test to yield valuable information which may ultimately resolve this apparent anomaly in comparative half-lives. References 1) M. Sakai, Nuclear Physics 33 (1962) 96 2) S. M. Brahmavar, A. S. Venkatesha Murthy and M. K. Ramaswamy, Nuclear Physics 58 (1964) 449 3) P. S. Jastram, W. L. Skeel and M. K. Kamaswamy, Bull. Am. Phys. So¢. 6 (1961) 38 4) J. M. Ferguson, Bull. Am. Phys. Soe..2 (1957) 395 5) M. K. Ramaswamy, Nuovo Cim. 26 (1962) 202
C O M P A R A T I V E H A L F - L I V E S O F AI = 3, N O B E T A T R A N S I T I O N S , IN EVEN NUCLEI s. M. BRAHMAVAR
Department of Physics, Panjab University, Chandigarh-3, India Received 9 April 1965 Abstract: The quantity log f,3t = log((S3)fot), which takes into account the dependence of the
shape factor S,3 in the integration over the spectrum, is expected to be a better constant for A1 = 3, no beta transitions, than the usualft value. A survey and analysis of all such transitions indicates anomalies for two transitions in ~6A1. I n recent years there have b e e n m a d e m a n y systematic studies of comparative halflives of various allowed beta transitions to even nuclei. O f these, the study 1) of allowed beta transitions from 1 +, 2 ÷ a n d 3 ÷ p a r e n t beta emitters has s h o w n h i n d r a n c e in all these transitions. A similar study 2) has m a d e it possible to propose a n empirical relation c o n n e c t i n g the energy ratios a n d the log f t values of beta transitions to v i b r a t i o n a l levels o f even nuclei. These studies i n n u c l e a r systematics have been useful i n u n d e r s t a n d i n g the basic n a t u r e of various beta transitions a n d the properties of low-lying excited states of even nuclei. A survey o f allowed a n d f o r b i d d e n beta transitions indicates that there is a small g r o u p o f beta transitions n a m e l y the u n i q u e second f o r b i d d e n A I = 3, n o transition, a b o u t which theory has something definite to say. Basically the q u a n t i t y TABLE 1
Comparative half-lives for AI = 3, no beta transitions Parent nucleus
Daughter nucleus
Type of transition
Energy of transition (MeV)
Comparative half-life
Ref.
1°Be
1°B
0+ ~ 3+
0.555
12.07
~, b)
2~Na
~2Ne
3+ --->0+
1.830
11.9
a. b)
~°A1
~6Mg
5+ ~ 2+ 5+ ~ 2+'
1.16 1.04
14.2 12.9
b) b)
e°Co
e°Ni
5+ --->2+
1.48
11.8
~)
a) D. C. Camp, L. M. Langer and D. R. Smith, Phys. Rev. 123 (1961) 241 b) Landolt-Bornstein: Energy levels of nuclei A = 5 to A ~ 257 (Springer-Verlag, 1961) Present address: Department of Physics and Astronomy Vanderbilt University, Nashville, Tennessee, USA. 79
80
S
M, BRAHMAVAR
log f 3 t = log ( ( S 3 ) f o t), which takes into account the dependence of the shape factor $23 in the integration over the spectrum, is expected to be a better constant for AI = 3, no beta transitions. Thus, an attempt has been made in this note to see how far this theoretical expectation is valid in such transitions. The data on A I = 3, no transitions, collected from various publications are presented in table 1, the columns o f which are selfexplanatory. Although the expected constancy is followed by three comparative half-lives, the anomalies for two transitions in 26A1 are quite surprising. Thus one is led to enquire into the large value of log f t for two such transitions in 26AI and test the validity of these as A1 = 3, no transitions. The experimental work of Jastram et al. 3) is not inconsistent with the 5 + ~ 2 + transition as a A1 -- 3, no interpretation obtained from spectral shape measurements 4)., Moreover this particular nucleus (26Mg) is expected t o lie in a region of transition toward a vibrational type o f spectrum and has exhibited interesting characteristics as regards the first excited state 5) and other low-lying states. It is deemed to be quite fruitful to put this nucleus to a precise experimental test to yield valuable information which may ultimately resolve this apparent anomaly in comparative half-lives. References 1) M. Sakai, Nuclear Physics 33 (1962) 96 2) S. M. Brahmavar, A. S. Venkatesha Murthy and M. K. Ramaswamy, Nuclear Physics 58 (1964) 449 3) P. S. Jastram, W. L. Skeel and M. K. Kamaswamy, Bull. Am. Phys. So¢. 6 (1961) 38 4) J. M. Ferguson, Bull. Am. Phys. Soe..2 (1957) 395 5) M. K. Ramaswamy, Nuovo Cim. 26 (1962) 202