Lifetime measurements in heavy elements using the charge plunger technique

这项研究旨在使用JyväskyläAccelerator实验室最近投入使用的电荷柱塞装置来测量重原子核的寿命。具有大内部转换系数的重元素的寿命测量被证明很难使用标准的柱塞技术，这是因为依赖于在不同速度区域(退化箔前后)的核衰变中产生的多普勒频移伽马射线的探测。对于具有高内部转换系数的原子核，一种补充方法是电荷柱塞技术；该技术是标准反冲距离多普勒频移(RDDS)方法的改进，该技术利用电荷重置箔，从而将离子的电荷重置为取决于其速度的值。一旦在目标的聚变-蒸发反应中产生，通过内部转换衰变的反冲核可能随后由于俄歇效应而使其离子电荷增加。改变靶到箔的距离允许通过计算在重置箔之前和之后发生的转换事件的数量来探测核寿命的敏感性。由此得到的反冲离子的电荷形状分布反映了它们在飞行期间发生的过程，并允许使用微分衰变曲线法(DDCM)或通过将贝特曼方程与数据拟合来提取核寿命。本研究的目的是利用上述电荷柱塞技术首次测量非同质异构态在No-254(可能还有其他转移原子核)中的寿命。

This research aims to measure lifetimes of heavy nuclei using the recently commissioned charge plunger device at the University of Jyväskylä Accelerator Laboratory. Lifetime measurements in heavy elements with large internal conversion coefficients prove difficult using standard plunger techniques, due to the reliance on the detection of Doppler shifted gamma-rays produced in nuclear decays at different velocity regions (before and after a degrader foil). A complementary approach for nuclei with high internal conversion coefficients is the charge plunger technique; a modification of the standard recoil distance Doppler-shift (RDDS) method, the technique utilises a charge reset foil, whereby the charge of ions is reset to a value dependent on their velocity. Once produced in fusion-evaporation reactions at a target, recoiling nuclei that decay via internal conversion may subsequently have their ionic charge increased due to the Auger effect. Varying the target-to-foil distance allows for the sensitivity of nuclear lifetimes to be probed, by counting the number of conversion events that occurred before and after the reset foil. The resulting charge shape distribution of recoil ions reflect the processes that occurred during their time of flight and allows for nuclear lifetimes to be extracted using the differential decay curve method (DDCM), or by fitting Bateman equations to the data. This research aims to make the first measurements of the lifetime of a non-isomeric state in No-254 (and possibly other transfermium nuclei) by employing the charge plunger technique described above.