### Abstract

The ratio of [Formula presented]- to [Formula presented]-shell electron captures in light nuclei is particularly sensitive to electron overlap and exchange effects. Calculations of these effects in [Formula presented] disagree by more than [Formula presented]. We report a measurement of the [Formula presented] ratio in [Formula presented], using a cryogenic microcalorimeter which clearly separates [Formula presented]- and [Formula presented]-shell captures. The obtained [Formula presented] ratio of 0.040(6) is less than half that of existing predictions for free [Formula presented]. The discrepancy is likely due to in-medium effects distorting the [Formula presented]-shell electron orbitals.

Original language | English (US) |
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Number of pages | 1 |

Journal | Physical Review Letters |

Volume | 88 |

Issue number | 1 |

DOIs | |

State | Published - Jan 1 2002 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

*Physical Review Letters*,

*88*(1). https://doi.org/10.1103/PhysRevLett.88.012501