LIFETIME STUDIES IN TELLURIUM-121
By delayed coincidence measurements, an upper limit of one nanosec was determined for the lifetime of the 214kev level nn Te/sup 121/. A Te/sup 121/ source (half life = 154 days) was produced by (p,n) reaction on natural Sb. Delayed coincidences were measured between the K x ray following the internal conversion of the 82-kev transition and the succeeding 214-kev gamma ray. For the prompt coincidence curve the coincidences between K x ray and 160-kev gamma ray, following the decay of 104-day Te/sup 123/ (which was simultaneously produced along with Te/sup 121/), were used. The 160-kev level is known to have a half life of 1.9 x 10/sup -10/ sec of delayed coincidence measurements, compared with the observed upper limit of one nanosec for the 214-kev level in Te/ sup 121/. This lifetime upper limit yields an upper limit of 400 for the M 1 retardation factor, which is not small enough to rule out the 1-forbidden assignment. 1forbidden M-1 transitions are known to be retarded by factors of 30 to 900 compared to single particle estimates. The internal conversion coefficient for the 214-kev transi-tion in Te/sup 121/ leads to M-1 assignment: The ground state of Te/sup 121/ is known to be one-half. ln this region there are available s1/2 and d1/2 single particle orbitals. The M-1 assignment for the 214- kev transition is consistent with the assumption that these configurations describe the ground state and first excited state respectively, with the condition, however, that the transition should be 1-forbidden ( DELTA 1 = 2) and consequently slower than the single particle speeds. (BBB)
- Research Organization:
- Karnatak Univ., Dharwar, India
- NSA Number:
- NSA-18-006193
- OSTI ID:
- 4131282
- Journal Information:
- Current Sci. (India), Journal Name: Current Sci. (India) Vol. Vol: 32
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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