Violation of the adiabatic approximation observed in vibrational structures of a molecular ion at the photoionization

为了研究分子框架中的K壳层光电子角分布，我们研制了一台高动量分辨率的多电子-离子符合动量成像仪。该装置由电子和离子飞行时间光谱仪、超音速样品射流和快速TDC系统组成。该系统由12位/100 MHz晶体振荡器计数器和7个时间-幅度转换器组成，可接收最多6个作为启动脉冲的信号和1个作为停止信号的信号。利用该装置测量了分子框架内分子的振动分辨光电子角分布，阐明了CO_2在O1s→_5σ_g^*形共振区振动分辨的O1S垫。使用部分…将PADS与理论计算进行了比较更松弛的Hartree-Fock近似，它阐明了分波分量在光电子发射的反对称伸缩振动模信号中的作用。然后，我们在N1s→σ^*形状共振区测量了来自NO的振动分辨和多重分辨的N1sPad。在NO的N1s电离区有两个极大值，分别位于413 eV和415 eV附近，它们被解释为σ^*形共振、抖动、抖动或交换分裂。人们发现，比较两个极大值周围的焊盘非常有趣，它们提供了关于小分子K壳层电子发射机制的丰富信息。此外，该装置还用于阐明CO_2、C_2H_2和NO_2等小分子在K壳层激发和/或电离后离子分解前的分子形变。综上所述，我们研制了多符合动量成像仪来获得分子框架内具有振动分辨率的光电子角分布，并阐明了小分子K壳层电子发射过程的详细机制。较少

We have developed a multiple electron-ion-coincidence momentum imaging apparatus with high momentum resolution using monochromatized undulator radiation at SPring-8, in order to study K-shell photoelectron angular distribution(PAD) in the molecular frame. This apparatus consists of electron and ion time-of-flight spectrometers with multi-hit two-dimensional position sensitive detectors, a supersonic jet of samples, and a fast TDC system, which is composed of 12 bits/100 MHz crystal oscillator counters and 7 time-to-amplitude converters and can receive signals up to 6 as start pulses and one signal as a stop signal. The time resolution of this TDC is about 120 ps under the time spam of 40 μs. Using this apparatus we have measured vibration-resolved photoelectron angular distributions of molecules in the molecular frame and clarified the vibration-resolved O 1s PADs from CO_2 in the O 1s→5σ_g^* shape resonance region. The PADs are compared with the theoretical calculation using a partial … More ly relaxed Hartree-Fock approximation, which elucidated a role of partial wave components in the anti-symmetric-stretching vibrational mode signals for photoelectron emission. Then, we have measured vibration- and multiplet-resolved N 1s PADs from NO in the N 1s→σ^* shape resonance region. There are two maxima in the N 1s ionization region of NO, around 413 and 415 eV, which were interpreted as σ^* shape resonance, shake up, shake off, or exchange splitting. It has been found very interesting to compare the PADs around the two maxima each other, which are giving fruitful information on electron emission mechanisms from the K-shell of small molecules. Further this apparatus has served for clarification of molecular deformation just before ionic decomposition following K-shell excitation and/or ionization in small molecules like CO_2,C_2H_2 and NO_2.In conclusion, we have developed the multi-coincidence momentum imaging apparatus for obtaining the photoelectron angular distributions with vibrational resolution in the molecular frame and clarified detailed mechanisms of photoelectron emission processes in the K-shell electrons of small molecules. Less