Electronic Final States in Nuclear $β$ Decay: A Sudden-Approximation Framework

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1. Verfasser: D'yakonov, G. V.
Format: Preprint
Veröffentlicht: 2026
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author D'yakonov, G. V.
author_facet D'yakonov, G. V.
contents Electronic final states generated by sudden changes of the Hamiltonian are studied here, with emphasis on nuclear charge variation in $β$ decay. A $λ$-parametrized family $\hat H(λ)$ that continuously connects the initial and final Hamiltonians, so that the electronic response can be represented as a continuous deformation in Hilbert space, is introduced. Within the sudden approximation, transition amplitudes are written as overlaps between eigenstates of distinct Hamiltonians. To relate non-orthogonal one-electron basis sets in a stable way, the paper uses a practical transport scheme based on overlap metrics and truncated singular value decomposition (SVD). This mapping is interpreted as a discrete counterpart of continuous transport along the $λ$ path. The formalism is first developed for the one-electron case, where analytic structure and selection rules are made explicit, and then generalized to many-electron systems via nonorthogonal determinant overlap expressions. The resulting formulation gives transition probabilities in bound and continuum channels in a way that is both numerically stable and easy to interpret.
format Preprint
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institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Electronic Final States in Nuclear $β$ Decay: A Sudden-Approximation Framework
D'yakonov, G. V.
Chemical Physics
Quantum Physics
Electronic final states generated by sudden changes of the Hamiltonian are studied here, with emphasis on nuclear charge variation in $β$ decay. A $λ$-parametrized family $\hat H(λ)$ that continuously connects the initial and final Hamiltonians, so that the electronic response can be represented as a continuous deformation in Hilbert space, is introduced. Within the sudden approximation, transition amplitudes are written as overlaps between eigenstates of distinct Hamiltonians. To relate non-orthogonal one-electron basis sets in a stable way, the paper uses a practical transport scheme based on overlap metrics and truncated singular value decomposition (SVD). This mapping is interpreted as a discrete counterpart of continuous transport along the $λ$ path. The formalism is first developed for the one-electron case, where analytic structure and selection rules are made explicit, and then generalized to many-electron systems via nonorthogonal determinant overlap expressions. The resulting formulation gives transition probabilities in bound and continuum channels in a way that is both numerically stable and easy to interpret.
title Electronic Final States in Nuclear $β$ Decay: A Sudden-Approximation Framework
topic Chemical Physics
Quantum Physics
url https://arxiv.org/abs/2604.23910