Doppler-free ablation fluorescence spectroscopy of Ca for high-resolution remote isotopic analysis
Doppler-free ablation fluorescence spectroscopy of Ca for high-resolution remote isotopic analysis
复制标题
DOI：
10.1039/d2ja00304j
复制
发表时间：
2023-01-17
影响因子：
3.4
通讯作者：
Hasegawa，Shuichi
中科院分区：
文献类型：
--
作者：
Miyabe，Masabumi;Kato，Masaaki;Hasegawa，Shuichi
为了开发具有小同位素位移的核素的远程同位素分析，使用激光烧蚀羽流对Ca进行了无多普勒荧光光谱分析。利用两个外腔二极管激光器的反传播激光束照射羽流，通过1S0→1P1→1D2的双共振方案将基态Ca原子激发到1D2态。随后，我们测量了从1D2到1P1态弛豫相关的荧光光谱。在70 Pa氦气压力下，烧蚀后延迟1 ms测得的线宽小于70 MHz，约为多普勒限制荧光光谱线宽的1/30。荧光光谱的时间变化在小于600 μs的延迟处观察到宽高斯基，这很可能是由变速碰撞引起的。此外，根据不同气体压力下测量的光谱，确定了第二步1P1→1D2转变的压力展宽速率系数为46.0 MHz / torr。我们利用三种天然存在的Ca同位素（即40Ca、42Ca和44Ca）的荧光信号评估了校准曲线的线性度、检出限和测量精度等分析性能。根据背景的3σ准则，估计同位素丰度的检出限为0.09%。这些结果表明，这种光谱技术有望用于同位素位移小的核素的远程同位素分析。
To develop remote isotopic analysis for the nuclides with small isotope shifts, Doppler-free fluorescence spectroscopy of Ca was performed using laser ablation plumes. Counter-propagating laser beams from two external cavity diode lasers were used to irradiate the plume in order to excite the ground-state Ca atoms to the 1D2 state through a double resonance scheme of 1S0 → 1P1 → 1D2. Subsequently, we measured fluorescence spectra associated with the relaxation from the 1D2 to 1P1 states. The linewidth measured at 1 ms delay after ablation under helium gas pressure of 70 Pa was found to be less than 70 MHz, which was about 1/30 of the linewidth of the Doppler-limited fluorescence spectrum. A broad Gaussian pedestal was observed at less than 600 μs delay in the temporal variation in fluorescence spectra, and it was most likely due to the velocity-changing collision. Additionally, the pressure broadening rate coefficient for the second-step 1P1 → 1D2 transition was determined to be 46.0 MHz per torr from the spectra measured under various gas pressures. We evaluated analytical performances such as linearity of the calibration curve, limit of detection, and measurement accuracy using fluorescence signals of three naturally occurring Ca isotopes (i.e., 40Ca, 42Ca, and 44Ca). The limit of detection of isotopic abundance was estimated to be 0.09% from the 3σ criteria of the background. These results suggest that this spectroscopic technique is promising for remote isotopic analysis of nuclides with small isotope shifts.