Control of photodissociation reaction of fluoromethane molecules using deformation in core-excited state

首先，设计并构建了由延迟线型阳极和微通道板组成的带有二维位置敏感探测器的Wiley-McLarlen型飞行时间质谱仪。仪器在水平方向上安装在真空室中。该腔室作为广岛大学HiSOR软x射线束线BL6的终端安装。同步辐射由高分辨率单色仪分散并引入腔室。用氮分子（N_2）测试了装置的性能。N_2的氮Is电子光激发后产生N^+、N^<++>碎片离子，并通过二维探测器检测到。在探测器上观察到的碎片离子图像显示为同心形状。基于核心激发线性分子光解的轴向反冲近似，这是非常合理的，其中解离比分子旋转快得多。接下来，通过测量探测器上的TOF光谱和位置图像，获得了N1s->σ^*激发后N^+和N^<++>的动量图像。由于Σ->Σ跃迁，得到的解离碎片离子的初始动量矢量向入射光的电矢量方向强烈分布。因此，仪器的性能是令人满意的。最后，研究了核心激发CHF_3分子在C - k边的衰变动力学。随着激发能的增加，H^+的动能分布峰值向高能侧移动。在C1s->3p共振激发下，（H^+- f ^+）和（H^+- c ^+）的H^+的动能分布比（H^+- cf_2 ^+）和（H^+- cf ^+）的H^+向高能侧移动。

At first, a Wiley-McLarlen type time-of-flight (TOF) mass spectrometer equipped with a two-dimensional position-sensitive detector, which was composed of a delay-line-type anode and Microchannel plates, was designed and constructed. The apparatus was installed into a vacuum chamber in the horizontal direction. The chamber was mounted as an endstation of the soft x-ray beamline BL6 of HiSOR in Hiroshima University. Synchrotron radiation was dispersed by a high-resolution monochromator and introduced into the chamber. Performance of the apparatus was tested using nitrogen molecule (N_2). Fragment ions (N^+, N^<++>) were produced after a photoexcitation of the nitrogen Is electron of N_2 and detected by the two-dimensional detector. The observed image for the fragment ions on the detector shows a concentric shape. This is quite reasonable based on the axial-recoil approximation in photodissociation of core-excited linear molecules, in which dissociation is much faster than molecular rotation.Next, the momentum images of N^+ and N^<++> were obtained after the N1s->σ^* resonant excitation by measuring the TOF spectra and position images on the detector. The obtained initial momentum vector of the fragment ion in dissociation is strongly distributed toward the direction of the electric vector of the incident light due to the Σ->Σ transition. Thus, the performance of the apparatus was satisfied sufficiently.Finally, the decay dynamics of core-excited CHF_3 molecule was investigated in the C K-edge. The peak of the kinetic-energy distribution of H^+ moves to high-energy side with the increase in excitation energy. At the C1s->3p resonant excitation, the kinetic-energy distributions of H^+ for (H^+-F^+) and (H^+-C^+) move to high-energy side in comparison with those for (H^+-CF_2^+) and (H^+-CF^+).