Nuclear spectroscopic studies of some very heavy odd-mass nuclides

Thesis/Dissertation · Tue Sep 20 04:00:00 EDT 1966

DOI:https://doi.org/10.2172/991026· OSTI ID:991026

Ahmad, Irshad ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The nuclear radiations of nuclides: U²³³, Pu²³⁹, Bk²⁴³, Bk²⁴⁴, Bk²⁴⁵, Bk²⁴⁶, Bk²⁴⁹, Cf²⁴⁹, and Fm²⁵⁵ were investigated with high-resolution spectrometers. The α-particle spectra of all nuclides except Bk²⁴⁹ were measured with 6 mm diameter surface-barrier detectors. Bk²⁴⁹ α-particles were analyzed with a double-focusing magnetic spectrograph. The γ-singles were examined with the recently developed Ge(Li) and Si(Li) detectors coupled with very-low noise 'internal FET' preamplifiers. Weak alpha groups were observed in coincidence with γ-rays, detected with a NaI(Tl) scintillation spectrometer. To improve the over-all coincidence efficiency a new coincidence apparatus was designed and built. This instrument consisted of a cooled 4.5 cm diameter semiconductor detector for α-particle detection and a 3 cm diameter by 2.7 cm long Ge(Li) detector for γ-ray analysis. The Ge(Li) detector could also be replaced with a NaI(Tl) detector. Cf²⁴⁹ conversion electrons were measured with a cooled Si(Li) detector coupled with an internal FET preamplifier. On the basis of the present work and previous information, energy-level diagrams of the daughter nuclei have been constructed. The levels have been grouped into rotational bands built on Nilsson single-particle states. Because of identification of several rotational members of the bands, definite Nilsson quantum number assignments have been made in most cases. The alpha intensity calculations of Poggenburg were found quite helpful in making these assignments. A strong Coriolis effect was observed in the Am²⁴⁵ levels populated by the alpha groups of Bk²⁴⁹. Calculations were made with Nilsson wave-functions, and these were found to agree with the experimental results. The Coriolis interaction was found important in almost all cases; the effect was very noticeable in the level spacings between the rotational members of the bands. High-lying bands in Cm²⁴⁵ (at 644 keV) and cf²⁵¹ (at 550 keV) were observed and 4 rotational members of each were identified. The modes of de-excitation of these levels indicate very small or no vibrational characters in them. This suggests that the vibrational bands, in this region lie at very high energies (~1 MeV) above the ground state.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: US Atomic Energy Commission (AEC)
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 991026
• Report Number(s): UCRL--16888
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
DE-EXCITATION
DETECTION
EFFICIENCY
ELECTRONS
GROUND STATES
ISOTOPES
LI-DRIFTED GE DETECTORS
LI-DRIFTED SI DETECTORS
NUCLEI
PREAMPLIFIERS
RADIATIONS
ROTATIONAL STATES
SCINTILLATIONS
SEMICONDUCTOR DETECTORS
SPECTRA
SPECTROMETERS
VIBRATIONAL STATES
WAVE FUNCTIONS