Cross sections for the formation of {sup 195}Hg{sup m,g}, {sup 197}Hg{sup m,g}, and {sup 196}Au{sup m,g} in {alpha} and {sup 3}He-particle induced reactions on Pt: Effect of level density parameters on the calculated isomeric cross-section ratio

Journal Article · Wed Mar 15 00:00:00 EST 2006 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PhysRevC.73.034613· OSTI ID:20771360

Sudar, S ^[1]; Qaim, S M ^[1]

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1. Institut fuer Nuklearchemie, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany)

Excitation functions were measured for the reactions {sup nat}Pt({sup 3}He,xn){sup 195}Hg{sup m,g},{sup nat}Pt({sup 3}He,xn){sup 197}Hg{sup m,g},{sup nat}Pt({sup 3}He,= x){sup 196}Au{sup m,g}, and {sup nat}Pt({alpha},xn){sup 197}Hg{sup m,g} over the energy range of 18-35 MeV for {sup 3}He particles and 17-26 MeV for {alpha} particles. The reactions {sup 197}Au(p,n){sup 197}Hg{sup m,g} were also investigated over the proton energy range of 6-20 MeV. The three projectiles were produced at the Juelich variable-energy compact cyclotron (CV 28). Use was made of the activation technique in combination with conventional high-resolution as well as low-energy HPGe-detector {gamma}-ray spectroscopy. For most of the reactions, the present measurements provide the first consistent sets of data. From the available experimental data, isomeric cross-section ratios were determined for the above-mentioned reactions. Nuclear model calculations using the code STAPRE, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of both the isomeric and the ground states of the products. The calculations were compared with the results of the EMPIRE-II code. The excitation functions of the ({sup 3}He,xn) and ({alpha},xn) processes are described well by the theory. In the case of ({sup 3}He,pxn) reactions, however, considerable deviations were observed between the experiment and the theory, presumably due to strong contributions from direct interactions. A description of the isomeric cross-section ratio by the model was possible only with a very low value of {eta}, i.e., the {theta}{sub eff}/{theta}{sub rig} ratio. A mass dependence of {eta} is proposed.

• OSTI ID: 20771360
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 73, Issue 3; Other Information: DOI: 10.1103/PhysRevC.73.034613; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA PARTICLES
ALPHA REACTIONS
ENERGY-LEVEL DENSITY
EXCITATION FUNCTIONS
EXCITON MODEL
GAMMA SPECTROSCOPY
GOLD 196
GOLD 197
GROUND STATES
HELIUM 3 REACTIONS
HIGH-PURITY GE DETECTORS
MERCURY 195
MERCURY 197
MEV RANGE
PLATINUM 194 TARGET
PLATINUM 195 TARGET
PLATINUM 196 TARGET
PROTONS
STATISTICAL MODELS