Paramagnetic Resonance Absorption in Crystals Colored by Irradiation

Abstract

LETTERS TO Nucleus Sr 90 Sr 91 Y 90 Y 91 Sb 125 Cs 137 (W> 2 -1)/*X10 10 0.4 0.7 0.3 0.8 1.1 1.8The criterion fits Sr 89 and K 42 ; in both cases shell model considerations support the assignment Al-±2 and change in parity. An excellent measurement of K 42 has already been made by Siegbahn. 9 It disintegrates ( Fig. 1) by negatron emission to the ground state of Ca 42 and also to an excited state followed by a gamma-ray. We have analyzed Siegbahn's data for the high energy component with results shown in Fig. 2 both for an allowed FK plot and again as a forbidden FK plot wherein the factor G is included. The bulging curvature of the one and the near-straightness of the other confirm the above-stated criterion as well as those aspects of the shell model and of the Fermi theory of beta-decay which are involved in this example.The shell model associates the odd configuration (3d) -1 (4/) 3 with the ground state of K 42 . Similarly the even configuration (4/) 2 may be associated with the ground state of Ca 42 (probably 1 = 0) and with low excited states (1=2, 4, and 6). We suggest 1 = 2 and even parity for the excited state of Ca 42 observed in the K 42 decay. The low energy transition is thus interpreted as first-forbidden with A/ = 0. * Assisted by the joint program of the ONR and the AEC. iE.

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