7
Wave Functions in the Vicinity
of Particle-Emission Threshold
7.1
Configuration Mixing in the Vicinity of the Dissociation
Threshold
What can be said about the properties of many-body states in the narrow range
of energies around the reaction threshold? Are they universal, independent of any
particular realization of the Hamiltonian? In other words, are the phenomena in
the neighborhood of reaction thresholds sufficiently specific to be considered as a
separate domain of interdisciplinary research, where nuclear phenomena share some
properties with near-threshold phenomena in atomic physics, molecular physics or
nanophysics?
The configuration mixing involving resonant states and background states of the
nonresonant scattering continuum is a source of collective features such as, e.g.
the resonance trapping [1–6] and super-radiance phenomenon [7, 8], multichannel
coupling effects in reaction cross sections [9–11] and shell occupancies [12], modification of spectral fluctuations[13], and deviations from Porter-Thomas resonance
widths distribution [6, 14, 15]. Another phenomenon which should be mentioned
in this context is the formation of correlated structures (clusters) in states close
to the cluster emission threshold. A comprehensive understanding of the universal
occurrence of clustering is absent in the closed quantum system formulation of the
nuclear many-body problem. The popular cluster model [16–22] is an a posteriori
approach that assumes a pre-existence of the clusters. A priori type approaches, like
the nuclear shell model, fail to predict the cluster states at observed low excitation
energies around the cluster-decay thresholds. This failure to predict and describe
cluster states in the closed quantum system framework is the central problem in
nuclear theory.
Ikeda et al. [23] noticed that α-cluster states can be found in the proximity
of α-particle decay thresholds. At that time, this important observation has not
raised much interest in studies of the coupling to particle-decay channels as the
general mechanism responsible for generating the correlations in near-threshold
© Springer International Publishing AG 2021
N. Michel, M. Płoszajczak, Gamow Shell Model, Lecture Notes in Physics 983,
https://doi.org/10.1007/978-3-030-69356-5_7
313
Wave Functions in the Vicinity
of Particle-Emission Threshold
7.1
Configuration Mixing in the Vicinity of the Dissociation
Threshold
What can be said about the properties of many-body states in the narrow range
of energies around the reaction threshold? Are they universal, independent of any
particular realization of the Hamiltonian? In other words, are the phenomena in
the neighborhood of reaction thresholds sufficiently specific to be considered as a
separate domain of interdisciplinary research, where nuclear phenomena share some
properties with near-threshold phenomena in atomic physics, molecular physics or
nanophysics?
The configuration mixing involving resonant states and background states of the
nonresonant scattering continuum is a source of collective features such as, e.g.
the resonance trapping [1–6] and super-radiance phenomenon [7, 8], multichannel
coupling effects in reaction cross sections [9–11] and shell occupancies [12], modification of spectral fluctuations[13], and deviations from Porter-Thomas resonance
widths distribution [6, 14, 15]. Another phenomenon which should be mentioned
in this context is the formation of correlated structures (clusters) in states close
to the cluster emission threshold. A comprehensive understanding of the universal
occurrence of clustering is absent in the closed quantum system formulation of the
nuclear many-body problem. The popular cluster model [16–22] is an a posteriori
approach that assumes a pre-existence of the clusters. A priori type approaches, like
the nuclear shell model, fail to predict the cluster states at observed low excitation
energies around the cluster-decay thresholds. This failure to predict and describe
cluster states in the closed quantum system framework is the central problem in
nuclear theory.
Ikeda et al. [23] noticed that α-cluster states can be found in the proximity
of α-particle decay thresholds. At that time, this important observation has not
raised much interest in studies of the coupling to particle-decay channels as the
general mechanism responsible for generating the correlations in near-threshold
© Springer International Publishing AG 2021
N. Michel, M. Płoszajczak, Gamow Shell Model, Lecture Notes in Physics 983,
https://doi.org/10.1007/978-3-030-69356-5_7
313