Nuclear Matrix Elements in the First-Forbidden Beta Decay of theEu152Ground State

Abstract

The degree of circular polarization P c (6p y ) and the directional correlation W(0p y ) = 1+^2(^)^2(00^7) were measured in the 3~(1.49-MeV jS~) -> 2 + (0.344-MeV 7) ->0 + /3-7 cascade leading from the ground state of Eu 152 to the Sm 152 ground state. The angle d$ y is the angle between the £ and 7 momentum vectors. Representative values of P c (0p y ) measured at W=3.20 (in units mc 2 ) for some average angles 6$ y are: P c (90°) = -0.01=b0.09, P c (130°) = +0.33±0.07, P c (157°)-0.33±0.07, P«(171°)=0.24±0.10. Some representative values of the directional correlation coefficient Az^W) are: ^2(2.8) = -0.335±0.006, ^4 2 (3.15) = -0.363dr0.006, A 2 (3A) = -0.381±0.005, 4 2 (3.7) = -0.388±0.004. The data were analyzed on an electronic digital computer on the basis of the Kotani parameters Y, u, x, and z. Information obtained about the nuclear matrix parameters may be summarized as follows: F=0.70db0.20, #=0.125±0.06, w=0.125db0.06, 3 = 1.0. Taken jointly with theft value of the 1.49-MeV (3 transition these parameters yield the nuclear matrix elements: y%/P = ±(2.9±0.4)X10~3, ,A/P==±(4.3rb2.3)XlO-4 , fioXr/R=*±(3.6±L9)XlO-*, y7a = :±:(2.5=fc:l.l)X10~4, where R is the nuclear radius of Eu 152 in units of h/tnc. These results reveal the importance of J* By relative to the other nuclear matrix elements which contribute to the decay. The experimental value of the matrix element ratio fiw.1 ft agrees with the prediction of the conserved vector current theory of beta decay.

Nuclear Orientation of 152Eu in Gold

“…which is in agreement with the results of Alexander and Steffen (1962) and Appalacharyulu et al (1969) A reorientation is observed in the 122 keY level of 15ZSm and we find…”

“…This result has been corrected for fourth order effects. Several authors (Alexander and Steffen 1962;Appalacharyulu et al 1969) have performed /3-y angular correlation and polarization measurements of this cascade. Their results have been expressed in terms of the Kotani (1959) parameters Y, x, U, z.…”

“…Where appropriate, the results presented in Table 1 have been corrected in this manner. o Value taken from Alexander and Steffen (1962).…”