The balance of the linear photon momentum in multiphoton ionization is studied experimentally. In the experiment argon and neon atoms are singly ionized by circularly polarized laser pulses with a wavelength of 800 nm and 1400 nm in the intensity range of 10 14 − 10 15 W/cm 2 . The photoelectrons are measured using velocity map imaging. We find that the photoelectrons carry linear momentum corresponding to the photons absorbed above the field free ionization threshold. Our finding has implications for concurrent models of the generation of terahertz radiation in filaments.

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Size-controllable tin oxide nanoparticles are prepared by heating ethylene glycol solutions containing SnCl 2 at atmospheric pressure. The particles were characterized by means of transmission electron microscopic (TEM), X-ray diffraction (XRD) studies. TEM micrographs show that the obtained material are spherical nanoparticles, the size and size distribution of which depends on the initial experimental conditions of pH value, reaction time, water concentration, and tin precursor concentration. The XRD pattern result shows that the obtained powder is SnO 2 with tetragonal crystalline structure. On the basis of UV/vis and FTIR characterization, the formation mechanism of SnO 2 nanoparticles is deduced. Moreover, the SnO 2 nanoparticles were employed to synthesize carbon-supported PtSnO 2 catalyst, and it exhibits surprisingly high promoting catalytic activity for ethanol electrooxidation.