Photoelectron spectroscopy without vacuum: nanoparticles in gas suspension

The photoelectric yield Y of nanoparticles in gas suspension delivers a fingerprint of the particle surface as it interacts with the surrounding gas, but bulk properties of the particle can also be probed. We show in three new experiments how this can be applied to acquire remarkable insight into processes of considerable general interest. In the first example, soot reduction by heterogeneous catalysis is examined. We show that fuel additives lead to the formation of transition metal oxide nuclei in the combustion zone. The carbonaceous matter preferentially condenses on the surface of the nuclei where it is burnt in the last stage of the combustion. In the second example, we present a method for the investigation of the desorption dynamics from particle surfaces using excimer laser pulses for photoemission. The kinetics of thermal perylene desorption from various types of particles is measured with a time resolution of a few milliseconds. The desorption follows a first order rate law and can be described by the Arrhenius model. In the third example, we show that there exists circular dichroism (CD) in photoemission from particles built with chiral molecules. The dependence of CD on the size of the nanoparticles shows that the crystalline order in the particles is important. (C) 1999 Elsevier Science B.V. All rights reserved.