Lifetimes of excited states in nuclei with mass number around A = 88 by means of the Doppler shift attenuation method

Technical Report · Thu Sep 20 04:00:00 EDT 1973

OSTI ID:4316232

Beens, W

Nuclei in the mass region around A = 88 are of interest since according to the shell model the /sup 88/Sr nucleus consists of protons and neutrons in closed shells. So in a simple approach the levels in nuclei with some additional particles may result from the excitation of the /sup 88/Sr core (collective model states) and by the rearrangement of particles outside this core (shell model states). In experiments on these nuclei lifetimes werc measured of nuclear states which decay by gamma emission. From an estimate with the aid of the single particle model the expected lifetimes are smaller than 10/sup -12/ s for a lot of levels in several nuclei. Depending on the length of the lifetime different methods can be applied. It is described why the Doppler shift attenuation method was chosen. This method applies the time dependence of the energy shift of gamma radiation emitted by moving excited nuclei. This time dependence and the reliability of the method are discussed. Since the energy shifts are expected to be small a test experiment on the first excited states in / sup 58/Ni was done in order to demonstrate that the used apparatus meets the requirements. The experiments carried out on the nuclei /sup 89/Y, /sup 91/Nb, / sup 90/Zr and /sup 8 8/Zr are described. After the determination of the lifetimes and the transition probabilities special attention is paid to the identification of shell model features and collective ones. (auth)

• Research Organization: Vrije Universiteit, Amsterdam (Netherlands)
• NSA Number: NSA-29-028260
• OSTI ID: 4316232
• Report Number(s): INIS-mf--1006
• Country of Publication: Netherlands
• Language: English

Related Subjects

*NIOBIUM 91-- ENERGY LEVELS
*YTTRIUM 89-- ENERGY LEVELS
*ZIRCONIUM 88-- ENERGY LEVELS
*ZIRCONIUM 90-- ENERGY LEVELS
COLLECTIVE MODEL
DOPPLER EFFECT
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
GAMMA RADIATION
KINETICS
LIFETIME
N68631* --Physics (Nuclear
Experimental)--Nuclear Properties & Reactions
59 <= A <= 89--Energy Levels & Transitions
PROBABILITY
SHELL MODELS