- Introduction

Currently, super—ne particles are getting a lot of attention associated with nanotechnology research. Such small-size particles can easily enter into the human body and often settle in the lungs and deeper areas and are suspected to cause various diseases.[1.1] Nanosize particles in the atmosphere are mainly produced by the combustion of fossil fuels such as in engines, and arti—cially nanostructured supermolecules are intensively produced as highly functional materials. There is a high risk that highly functional materials are dispersed into the air from nanotechnology factories. Although nanosize particles make up only a small percentage of particle total mass, they account for a majority of the particle number (more than 90% of the particle number in diesel engine exhaust[1.2]), and their harmful in›uences on human health are being very seriously considered. It is rather dif—cult to estimate emissive conditions using conventional methods, and new evaluation criteria are required for a better understanding of their characteristics. It remains dif—cult to monitor the compositions and organic substances in nanoparticles because of the limited amount of nanoparticle constituents as well as their complexity.[1.3]

There are numerous standard methods to detect system parameters such as temperature and species concentrations, and these consist of well-known “industrial standards.” Although these standard methods are well established and easily accessible, they often have limited performance in terms of meeting industrial needs because of slow response, complicated preconcentration procedures, and so on. In contrast, laser diagnostics make it possible to monitor these parameters because of their fast response, high sensitivity, and noncontact features. This fast response is critical for the control of industrial systems, and the noncontact detection is necessary for the clari—cation of their phenomena.