Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA.
Department of Physics, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom.
Phys Rev Lett. 2023 Mar 3;130(9):093001. doi: 10.1103/PhysRevLett.130.093001.
We extend covariance velocity map ion imaging to four particles, establishing cumulant mapping and allowing for measurements that provide insights usually associated with coincidence detection, but at much higher count rates. Without correction, a fourfold covariance analysis is contaminated by the pairwise correlations of uncorrelated events, but we have addressed this with the calculation of a full cumulant, which subtracts pairwise correlations. We demonstrate the approach on the four-body breakup of formaldehyde following strong field multiple ionization in few-cycle laser pulses. We compare Coulomb explosion imaging for two different pulse durations (30 and 6 fs), highlighting the dynamics that can take place on ultrafast timescales. These results have important implications for Coulomb explosion imaging as a tool for studying ultrafast structural changes in molecules, a capability that is especially desirable for high-count-rate x-ray free-electron laser experiments.
我们将协方差速度图离子成像扩展到四个粒子，建立累积映射，并允许进行测量，这些测量提供了通常与符合检测相关的见解，但计数率要高得多。未经修正，四重协方差分析会受到不相关事件的两两相关的污染，但我们已经通过计算完整的累积量来解决这个问题，该累积量减去了两两相关。我们在几周期激光脉冲中强场多电离后甲醛的四体断裂中展示了这种方法。我们比较了两种不同脉冲持续时间（30 和 6 fs）的库仑爆炸成像，突出了超快时间尺度上可能发生的动力学。这些结果对库仑爆炸成像作为研究分子超快结构变化的工具具有重要意义，这种能力对于高计数率 X 射线自由电子激光实验尤其可取。
