We present state-selective measurements on the + H⁺ and NH⁺ + H⁺ + H dissociation channels following single-photon double ionization at 61.5 eV of neutral NH₃, where the two photoelectrons and two cations are measured in coincidence using 3D momentum imaging. Three dication electronic states are identified to contribute to the + H⁺ dissociation channel, where the excitation in one of the three states undergoes intersystem crossing prior to dissociation, producing a cold fragment. In contrast, the other two states directly dissociate, producing a ro-vibrationally excited fragment with roughly 1 eV of internal energy. The NH⁺ + H⁺ + H channel is fed by direct dissociation from three intermediate dication states, one of which is shared with the + H⁺ channel. We find evidence of autoionization contributing to each of the double ionization channels. The distributions of the relative emission angle between the two photoelectrons, as well as the relative angle between the recoil axis of the molecular breakup and the polarization vector of the ionizing field, are also presented to provide insight on both the photoionization and photodissociation mechanisms for the different dication states.

我们在中性NH ₃为61.5 eV的单光子双电离后，在+ H ⁺和NH ⁺ + H ⁺ + H解离通道上提供状态选择性测量，其中使用3D动量成像同时测量两个光电子和两个阳离子。识别出三个指示电子状态有助于+ H ⁺离解通道，其中三个状态之一的激发在离解之前经历了系统间交叉，从而产生冷碎片。相反，其他两个状态直接解离，产生具有大约1 eV内部能量的旋转振动激发的碎片。NH ⁺ + H⁺ + H通道通过直接解离三个中间指示状态来馈送，其中一种与+ H ⁺通道共享。我们发现自动电离有助于每个双电离通道的证据。还介绍了两个光电子之间的相对发射角的分布，以及分子分解的反冲轴和电离场的极化矢量之间的相对角，以提供有关该离子的光电离和光解离机理的见解。不同的使用状态。