Emission temperatures from the decay of particle-unstable complex nuclei

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5190378

Nayak, T K

Relative populations of particle-unstable states were measured for complex fragments emitted in the reaction {sup 14}N + Ag at E/A = 35 MeV by using a position sensitive high resolution hodoscope. Experimental population probabilities of particle-unstable states were extracted by fitting the coincidence spectra of the decay products by an appropriate R-matrix or Breit-Wigner formalism. According to thermal models, the populations of excited states at freezeout are expected to follow a Boltzmann distribution weighted by the emission temperature of the system. Tests of this freezeout assumption were made by comparing the experimental population to the predictions of statistical calculations. Extensive statistical calculation which include the effect of sequential feeding from heavier particle unstable nuclei were performed to estimate the population probabilities and the ratios of population probabilities indicate emission temperatures of about 3-4 MeV. But a detailed comparison for individual fragments for a calculation with T{sub em} = 4 MeV reveals that about half of the measured population probabilities and one third of the ratios of the population probabilities differ significantly from the predictions of statistical calculations. Calculations which include rotational effects could not satisfactorily account for this discrepancy. These results suggest a possible breakdown of the assumption of local thermal equilibrium at freezeout.

• Research Organization: Michigan State Univ., East Lansing, MI (United States)
• OSTI ID: 5190378
• Country of Publication: United States
• Language: English

Related Subjects

663450* -- Heavy-Ion-Induced Reactions & Scattering-- (1992-)
663590 -- Nuclear Mass Ranges-- A=220 & Above-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BREIT-WIGNER FORMULA
CHARGED-PARTICLE REACTIONS
COMPARATIVE EVALUATIONS
ELEMENTS
ENERGY LEVELS
ENERGY RANGE
EQUILIBRIUM
EVALUATION
EXCITED STATES
HEAVY ION REACTIONS
HODOSCOPES
KINETICS
LTE
MATHEMATICS
MATRICES
MEASURING INSTRUMENTS
METALS
MEV RANGE
MEV RANGE 10-100
NITROGEN 14 REACTIONS
NUCLEAR FRAGMENTS
NUCLEAR REACTION KINETICS
NUCLEAR REACTION YIELD
NUCLEAR REACTIONS
POSITION SENSITIVE DETECTORS
PROPORTIONAL COUNTERS
R MATRIX
RADIATION DETECTORS
REACTION KINETICS
SILVER
STATISTICS
TRANSITION ELEMENTS
YIELDS