$^{20}$ Mg（$βpγ$）$^{19}$ Ne衰变的多普勒展宽
Doppler Broadening in $^{20}$Mg($βpγ$)$^{19}$Ne Decay
摘要：
背景资料：I型X射线爆发中的$^{15}$ O（$α,γ$）$^{19}$ Ne瓶颈反应是最需要实验约束的热核反应速率，以提高爆发光变曲线模拟的精度。一种确定该反应热核速率的建议技术采用$^{20}$ Mg（$βpα$）$^{15}$ O衰变序列。目前已知，在4.03 MeV激发下的关键$^{15}$ O（$α,γ$）$^{19}$ Ne共振被注入$^{20}$ Mg（$βpγ$）$^{19}$ Ne中;然而，注入4.03 MeV状态的质子的能量尚不清楚。质子能量的知识将有助于未来的$^{20}$ Mg（$βp α$）$^{15}$ O测量。目的：测定$^{19}$ Ne的4.03 MeV质子跃迁能量。方法：将$^{20}$ Mg的快束注入塑料闪烁体中，用于探测$β$颗粒。使用16个高纯度锗探测器来探测$βp$衰变后发射的$γ$射线。用Monte Carlo方法模拟了$^{19}$ Ne $γ$射线的多普勒展宽，并与实验数据进行了比较。结果如下：质子和供给4.03 MeV状态的$^{19}$ Ne之间的质心能量被测量为1.21 ${^{+0.25}_{-0.22}}$ MeV，对应于7.44 ${^{+0.25}_{-0.22}}$ MeV的$^{20}$ Na激发能量。测定了包括1615 keV能级在内的$^{19}$ Ne态的绝对馈电强度和$γ$ -衰变分支比.报道了一个新的从$^{19}$ Ne的1536 keV态到基态的$γ$衰变分支。$^{19}$ Ne中1507 keV态的寿命测量为4.3 ${^{+1.3}_{-1.1}}$ ps，解决了文献中的差异。澄清了已发表文献中对$^{20}$ Mg（$βp$）衰变方案的误解。
英文摘要：
Background: The $^{15}$O($α,γ$)$^{19}$Ne bottleneck reaction in Type I x-ray bursts is the most important thermonuclear reaction rate to constrain experimentally, in order to improve the accuracy of burst light-curve simulations. A proposed technique to determine the thermonuclear rate of this reaction employs the $^{20}$Mg($βpα$)$^{15}$O decay sequence. The key $^{15}$O($α,γ$)$^{19}$Ne resonance at an excitation of 4.03 MeV is now known to be fed in $^{20}$Mg($βpγ$)$^{19}$Ne; however, the energies of the protons feeding the 4.03 MeV state are unknown. Knowledge of the proton energies will facilitate future $^{20}$Mg($βp α$)$^{15}$O measurements. Purpose: To determine the energy of the proton transition feeding the 4.03 MeV state in $^{19}$Ne. Method: A fast beam of $^{20}$Mg was implanted into a plastic scintillator, which was used to detect $β$ particles. 16 high purity germanium detectors were used to detect $γ$ rays emitted following $βp$ decay. A Monte Carlo method was used to simulate the Doppler broadening of $^{19}$Ne $γ$ rays and compare to the experimental data. Results: The center of mass energy between the proton and $^{19}$Ne, feeding the 4.03 MeV state, is measured to be 1.21${^{+0.25}_{-0.22}}$ MeV, corresponding to a $^{20}$Na excitation energy of 7.44${^{+0.25}_{-0.22}}$ MeV. Absolute feeding intensities and $γ$-decay branching ratios of $^{19}$Ne states were determined including the 1615 keV state. A new $γ$ decay branch from the 1536 keV state in $^{19}$Ne to the ground state is reported. The lifetime of the 1507 keV state in $^{19}$Ne is measured to be 4.3${^{+1.3}_{-1.1}}$ ps resolving discrepancies in the literature. Conflicting $^{20}$Mg($βp$) decay schemes in published literature are clarified.
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