ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantu... more ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantum mechanical S-matrix by solving the associated set of coupled second-order ordinary differential equations that describes the inelastic collisions between atomic particles. The only assumption is that the interaction matrix element between each pair of channels (say, γ and β) is of the form Uγ Semiclassical techniques can be incorporated directly in the theory if the Schrödinger equations for the uncoupled channels allow this treatment. The formulation is particularized to the two-channel problem and illustrated with a semiclassical example the He
The interaction of neutrons with matter has been simulted. Results regarding moderation, and retr... more The interaction of neutrons with matter has been simulted. Results regarding moderation, and retrodispersion in paraffin and ICRU material, both of interest in neutron dosimetry, are presented.
An analytical function deduced from Order Statistics is able to analytically reproduce lengthy Mo... more An analytical function deduced from Order Statistics is able to analytically reproduce lengthy Monte Carlo simulated Energy-Ordered Spectra obtained from heavy ion fusion-evaporation reactions in the case in which the level density is given by Constant Temperature Fermi Gas and the E1 gamma strength by the classical dipole law.
The Neutron Backscattering technique is tested when performing the task of localizing hydrogenate... more The Neutron Backscattering technique is tested when performing the task of localizing hydrogenated explosives hidden in soil. Detector system, landmine, soil and neutron source are simulated with Geant4 in order to obtain the number of neutrons detected when several parameters like mine composition, relative position mine-source and soil moisture are varied.
ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantu... more ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantum mechanical S-matrix by solving the associated set of coupled second-order ordinary differential equations that describes the inelastic collisions between atomic particles. The only assumption is that the interaction matrix element between each pair of channels (say, γ and β) is of the form Uγ Semiclassical techniques can be incorporated directly in the theory if the Schrödinger equations for the uncoupled channels allow this treatment. The formulation is particularized to the two-channel problem and illustrated with a semiclassical example the He
Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc(Gammasph... more Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc(Gammasphere) and the uc(Microball) to study the high-spin structure of the transitional nucleus ^87Nb. The first experiment using a thin target provided a considerable extension and refinement of the level and decay scheme, as well as firm spin assignments from DCO ratios. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of ε2 0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transitions between some pairs of bands. The experimental results were compared with calculations performed within the configuration-dependent shell-correction approach using a cranked Nilsson potential. The calculations generally reproduce the irregularities in the band structure and plunging Qt values, explaining them as reflect...
A simulation procedure to calculate some important parameters to the application of Order Statist... more A simulation procedure to calculate some important parameters to the application of Order Statistics in the analysis of continuum gamma decay is presented.
A comprehensive high-spin decay scheme has been deduced for 57Co using the Gammasphere Germanium ... more A comprehensive high-spin decay scheme has been deduced for 57Co using the Gammasphere Germanium detector array coupled to the 4pi charged-particle detector system Microball. Following the fusion-evaporation reaction of 28Si(36Ar,1alpha3p)57Co at 136 MeV beam energy about 90 excited states have been observed in 57Co, which are connected by some 230 gamma-ray transitions. The proposed level scheme reaches 16 MeV excitation
International Journal of Modern Physics: Conference Series, 2014
A gamma-backscattering imaging device dubbed Compton Camera, developed at GSI (Darmstadt, Germany... more A gamma-backscattering imaging device dubbed Compton Camera, developed at GSI (Darmstadt, Germany) and modified and studied at the Nuclear Physics Group of the National University of Colombia in Bogotá, uses the back-to-back emission of two gamma rays in the positron annihilation to construct a bidimensional image that represents the distribution of matter in the field-of-view of the camera. This imaging capability can be used in a host of different situations, for example, to identify and study deposition and structural defects, and to help locating concealed objects, to name just two cases. In order to increase the understanding of the response of the Compton Camera and, in particular, its image formation process, and to assist in the data analysis, a simulation of the camera was developed using the GEANT4 simulation toolkit. In this work, the images resulting from different experimental conditions are shown. The simulated images and their comparison with the experimental ones already suggest methods to improve the present experimental device
The location of objects hidden in dense matter and the analysis of metallic surfaces using gamma ... more The location of objects hidden in dense matter and the analysis of metallic surfaces using gamma backscattering are two possible applications strongly suggested here with experiments, highlevel Monte Carlo simulations, and some supporting basic theory.
... 6 , J. Döring 7 , FE Durham 8 , P.-F. Hua 4 , GD Johns 7 , M. Korolija 4 , DR LaFosse 4 , E. ... more ... 6 , J. Döring 7 , FE Durham 8 , P.-F. Hua 4 , GD Johns 7 , M. Korolija 4 , DR LaFosse 4 , E. Landulfo 6 , AO Macchiavelli 5 , W ... Louis, Missouri 63130 5 Nuclear Science Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 6 Department of Physics and Astronomy ...
High-spin states in 77 Kr were identified via analysis of prompt ␥-␥ coincidences in the 58 Ni( 2... more High-spin states in 77 Kr were identified via analysis of prompt ␥-␥ coincidences in the 58 Ni( 29 Si,2␣2p) reaction at 128 MeV at the Gammasphere facility. Evaporation channel selection was achieved using the 95 element Microball charged-particle detector. 27 new states and 42 new transitions were found. The positiveparity bands were confirmed and the ␣ϭϪ 1 2 band extended to 39 2 ϩ . The negative-parity signature pair was extended to 31 2 Ϫ and 37 2 Ϫ . Two new high-lying negative-parity bands were found extending from a state of spin Iϭ 15 2 and energy 2.6 MeV to 17.4 MeV at Iϭ( 55 2 )
ABSTRACT Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc... more ABSTRACT Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc(Gammasphere) and the uc(Microball) to study the high-spin structure of the transitional nucleus ^87Nb. The first experiment using a thin target provided a considerable extension and refinement of the level and decay scheme, as well as firm spin assignments from DCO ratios. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of ε2 0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transitions between some pairs of bands. The experimental results were compared with calculations performed within the configuration-dependent shell-correction approach using a cranked Nilsson potential. The calculations generally reproduce the irregularities in the band structure and plunging Qt values, explaining them as reflections of the underlying microscopic shell structure leading to band terminations.
ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantu... more ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantum mechanical S-matrix by solving the associated set of coupled second-order ordinary differential equations that describes the inelastic collisions between atomic particles. The only assumption is that the interaction matrix element between each pair of channels (say, γ and β) is of the form Uγ Semiclassical techniques can be incorporated directly in the theory if the Schrödinger equations for the uncoupled channels allow this treatment. The formulation is particularized to the two-channel problem and illustrated with a semiclassical example the He
The interaction of neutrons with matter has been simulted. Results regarding moderation, and retr... more The interaction of neutrons with matter has been simulted. Results regarding moderation, and retrodispersion in paraffin and ICRU material, both of interest in neutron dosimetry, are presented.
An analytical function deduced from Order Statistics is able to analytically reproduce lengthy Mo... more An analytical function deduced from Order Statistics is able to analytically reproduce lengthy Monte Carlo simulated Energy-Ordered Spectra obtained from heavy ion fusion-evaporation reactions in the case in which the level density is given by Constant Temperature Fermi Gas and the E1 gamma strength by the classical dipole law.
The Neutron Backscattering technique is tested when performing the task of localizing hydrogenate... more The Neutron Backscattering technique is tested when performing the task of localizing hydrogenated explosives hidden in soil. Detector system, landmine, soil and neutron source are simulated with Geant4 in order to obtain the number of neutrons detected when several parameters like mine composition, relative position mine-source and soil moisture are varied.
ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantu... more ABSTRACT We introduce a multichannel “potential curves hopping” model and obtain the exact quantum mechanical S-matrix by solving the associated set of coupled second-order ordinary differential equations that describes the inelastic collisions between atomic particles. The only assumption is that the interaction matrix element between each pair of channels (say, γ and β) is of the form Uγ Semiclassical techniques can be incorporated directly in the theory if the Schrödinger equations for the uncoupled channels allow this treatment. The formulation is particularized to the two-channel problem and illustrated with a semiclassical example the He
Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc(Gammasph... more Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc(Gammasphere) and the uc(Microball) to study the high-spin structure of the transitional nucleus ^87Nb. The first experiment using a thin target provided a considerable extension and refinement of the level and decay scheme, as well as firm spin assignments from DCO ratios. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of ε2 0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transitions between some pairs of bands. The experimental results were compared with calculations performed within the configuration-dependent shell-correction approach using a cranked Nilsson potential. The calculations generally reproduce the irregularities in the band structure and plunging Qt values, explaining them as reflect...
A simulation procedure to calculate some important parameters to the application of Order Statist... more A simulation procedure to calculate some important parameters to the application of Order Statistics in the analysis of continuum gamma decay is presented.
A comprehensive high-spin decay scheme has been deduced for 57Co using the Gammasphere Germanium ... more A comprehensive high-spin decay scheme has been deduced for 57Co using the Gammasphere Germanium detector array coupled to the 4pi charged-particle detector system Microball. Following the fusion-evaporation reaction of 28Si(36Ar,1alpha3p)57Co at 136 MeV beam energy about 90 excited states have been observed in 57Co, which are connected by some 230 gamma-ray transitions. The proposed level scheme reaches 16 MeV excitation
International Journal of Modern Physics: Conference Series, 2014
A gamma-backscattering imaging device dubbed Compton Camera, developed at GSI (Darmstadt, Germany... more A gamma-backscattering imaging device dubbed Compton Camera, developed at GSI (Darmstadt, Germany) and modified and studied at the Nuclear Physics Group of the National University of Colombia in Bogotá, uses the back-to-back emission of two gamma rays in the positron annihilation to construct a bidimensional image that represents the distribution of matter in the field-of-view of the camera. This imaging capability can be used in a host of different situations, for example, to identify and study deposition and structural defects, and to help locating concealed objects, to name just two cases. In order to increase the understanding of the response of the Compton Camera and, in particular, its image formation process, and to assist in the data analysis, a simulation of the camera was developed using the GEANT4 simulation toolkit. In this work, the images resulting from different experimental conditions are shown. The simulated images and their comparison with the experimental ones already suggest methods to improve the present experimental device
The location of objects hidden in dense matter and the analysis of metallic surfaces using gamma ... more The location of objects hidden in dense matter and the analysis of metallic surfaces using gamma backscattering are two possible applications strongly suggested here with experiments, highlevel Monte Carlo simulations, and some supporting basic theory.
... 6 , J. Döring 7 , FE Durham 8 , P.-F. Hua 4 , GD Johns 7 , M. Korolija 4 , DR LaFosse 4 , E. ... more ... 6 , J. Döring 7 , FE Durham 8 , P.-F. Hua 4 , GD Johns 7 , M. Korolija 4 , DR LaFosse 4 , E. Landulfo 6 , AO Macchiavelli 5 , W ... Louis, Missouri 63130 5 Nuclear Science Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 6 Department of Physics and Astronomy ...
High-spin states in 77 Kr were identified via analysis of prompt ␥-␥ coincidences in the 58 Ni( 2... more High-spin states in 77 Kr were identified via analysis of prompt ␥-␥ coincidences in the 58 Ni( 29 Si,2␣2p) reaction at 128 MeV at the Gammasphere facility. Evaporation channel selection was achieved using the 95 element Microball charged-particle detector. 27 new states and 42 new transitions were found. The positiveparity bands were confirmed and the ␣ϭϪ 1 2 band extended to 39 2 ϩ . The negative-parity signature pair was extended to 31 2 Ϫ and 37 2 Ϫ . Two new high-lying negative-parity bands were found extending from a state of spin Iϭ 15 2 and energy 2.6 MeV to 17.4 MeV at Iϭ( 55 2 )
ABSTRACT Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc... more ABSTRACT Two Experiments have been performed using the ^32S(^58Ni,3p) reaction at 135 MeV with uc(Gammasphere) and the uc(Microball) to study the high-spin structure of the transitional nucleus ^87Nb. The first experiment using a thin target provided a considerable extension and refinement of the level and decay scheme, as well as firm spin assignments from DCO ratios. Sub-picosecond lifetimes were measured in the second backed-target experiment using the Doppler-shift attenuation method. The lifetimes imply a rather modest average deformation of ε2 0.1, but with considerable variation from state to state. Strong alternations were observed in the B(M1) strengths of transitions between some pairs of bands. The experimental results were compared with calculations performed within the configuration-dependent shell-correction approach using a cranked Nilsson potential. The calculations generally reproduce the irregularities in the band structure and plunging Qt values, explaining them as reflections of the underlying microscopic shell structure leading to band terminations.
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