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Observación de la desintegración nuclear doble gamma competitiva
C Walz1, H Scheit1, N Pietralla1
1Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.
Nature
|October 16, 2015
Resumen
Los investigadores observaron una doble desintegración gamma (γγ) en estados nucleares excitados, un proceso cuántico raro. Este hallazgo amplía nuestra comprensión de la estructura nuclear y la electrodinámica cuántica más allá de las transiciones previamente estudiadas de 0 ((+) a 0 ((+)).
Área de la Ciencia:
- Física nuclear
- La electrodinámica cuántica
Sus antecedentes:
- La doble desintegración gamma (γγ) es un proceso fundamental de electrodinámica cuántica de segundo orden que implica la emisión simultánea de dos cuantos gamma.
- Anteriormente, la desintegración γγ solo se observaba para transiciones nucleares específicas (J ((π) = 0 ((+) → 0 ((+)) donde la desintegración gamma única está prohibida.
- La descomposición gamma (γ) única es el desafío experimental principal para observar la descomposición γγ.
Objetivo del estudio:
- Informar la observación de γγ-desintegración desde un estado nuclear excitado con J(π) = 11/2(-).
- Investigar la descomposición γγ que compite directamente con la descomposición γγ única permitida.
- Determinar la relación de ramificación y las multipolaridades del proceso de descomposición γγ.
Principales métodos:
- Observación experimental de la γγ-desintegración en el isómero 11/2(-) del bario-137 ((137) Ba).
- Medición de la correlación angular y de los espectros de energía de los rayos gamma emitidos.
- Cálculo de los elementos de la matriz de transición utilizando el modelo de cuasipartícula-fonón.
Principales resultados:
- Se observó que la γγ-desintegración del isómero 11/2(-) de (137) Ba compite con la γ-desintegración permitida al estado básico 3/2(+).
- Se determinó que la relación de ramificación para esta γγ-desintegración competitiva es de (2,05 ± 0,37) × 10 ((-6).
- El análisis de las correlaciones angulares y los espectros de energía permitieron la determinación de las multipolaridades contribuyentes.
Conclusiones:
- La γγ-desintegración observada proporciona una nueva vía para sondear la estructura nuclear.
- Este modo de descomposición ofrece acceso a propiedades nucleares previamente inexploradas, incluidas las polarizabilidades eléctricas nucleares generalizadas y las susceptibilidades magnéticas.
- El modelo cuasi partícula-fonón reproduce con éxito las mediciones experimentales.
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