Within the framework of the density matrix method, general formulas obtained that are convenient for describing fast pulsed photoemission that occurs in a time less than or on the order of the times of relaxation processes inside the photocathode. Expressions for the elements of the density matrix are found by solving the kinetic equation that takes into account the alternating electromagnetic field of light pumping and inelastic scattering of electrons. The derived formulas are applied for the numerical-analytical study of a one-dimensional model of wave-like spatiotemporal modulation of a photoelectron pulse of suitable duration during its passage through a double-well quantum-well heterostructure deposited on a volumetric planar photocathode. This modulation is a quantum beat that occurs as a result of excitation and subsequent slow oscillatory decay of the superposition of the doublet of quasi-stationary states of the heterostructure. It is possible to provide prolongation of generation and even amplification of waves of charge density and current density of photoelectrons when the photocathode is exposed to a periodic sequence of light pulses.
Spin- and angle-resolved photoemission studies of the electronic structure of Si(110)"16x2" surfaces
用自旋和角分辨光电子能谱研究了Si（110）“16 × 2”双畴、单畴和1 × 1表面的电子结构。使用水平和垂直偏振的60 eV和80 eV光子进行角分辨光电发射。带色散图显示了四个表面状态（$S_1$到$S_4$），这些状态被分配给硅悬挂键的基础上测得的结合能和水平和垂直光偏振之间的光发射强度变化。在Si（110）“16 × 2”重构中观察到的三种表面态（$S_1$、$S_2$和$S_4$）被分配给存在于波纹状平台结构边缘的Si吸附原子和Si原子。在Si（110）“16 x 2”和1 x 1能带图中仅观察到四种表面态之一，$S_3$，因此归因于作为Si（110）“16 x 2”和1 x 1表面的组分的普遍Si之字形链。体带区域中的状态归因于面内键。所有数据与Si（110）“16 × 2”表面的原子屈曲模型一致。虽然$P_y$和$P_z$的室温测量值在统计学上与零相容，但对映体A型和B型Si（110）“16 x 2”表面的$P_x$测量值给出了约1.5%的小平均偏振，其符号相反。在77 K下对A型Si（110）“16 x 2”表面的进一步测量给出了+0.3\%的较小值。因此，对于纵向极化，可以采用$\sim1\%$的上限。
A continuous-wave and pulsed X-band electron spin resonance spectrometer operating in ultra-high vacuum for the study of low dimensional spin ensembles
