競争的なダブル・ガンマ核崩壊の観測
C Walz1, H Scheit1, N Pietralla1
1Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany.
Nature
|October 16, 2015
まとめ
研究者達は 刺激された核の状態で 二重のガンマ (γγ) 崩壊を観測しました これは希少な量子過程です この発見は,以前に研究された 0 ((+)) から 0 ((+)) への移行を超えて,核構造と量子電動学の理解を拡大します.
科学分野:
- 核物理学
- 量子電動学
背景:
- ダブル・ガンマ (γγ) 崩壊は,2つのガンマ量子を同時に放出する基本的な二次量子力学プロセスである.
- 以前は,単一ガンマ分解が禁止されている特定の核移行 (J ((π) = 0 ((+)) → 0 ((+)) のみで,γγ-分解が観察されていた.
- シングル・ガンマ (γ) 腐敗は,γ-腐敗を観察するための主要な実験課題である.
研究 の 目的:
- J(π) = 11/2(-の興奮核状態から γγ-分解の観測を報告する.
- 許容される単一のg-decayと直接競合するg-decayを調査する.
- γγ分解プロセスの分岐比と多極性を決定する.
主な方法:
- バリウム-137 ((137) Ba) の 11/2 ((-) イソメールにおける γγ-分解の実験的観測.
- 放射されたガンマ線の角相関とエネルギースペクトルの測定.
- 準粒子-フォノンモデルを用いた移行行列要素の計算.
主要な成果:
- (137) Baの11/2(-) イソメールのγγ-分解は,許容されるγ-分解と3/2(+) 基底状態に競合することが観察された.
- この競争性 γγ-腐敗の分岐比は (2.05 ± 0.37) × 10 ((−6) と決定された.
- 角度相関とエネルギースペクトルの分析により,多極性の貢献を決定することができました.
結論:
- 観測された γγ-崩壊は,核構造を調査するための新しい経路を提供します.
- この崩壊モードは,一般化された核電極化性と磁気感受性を含む,これまで未知の核特性へのアクセスを提供します.
- 準粒子-フォノンモデルは実験的な測定を成功裏に再現します.
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