Abstract
Nano-sized organic aerosols, nanoparticles (d_p < 50 nm), in the atmosphere have attracted a lot of attention in recent years because of adverse effects on human health. A new system combining a soft plasma ionization (SPI) source with a time-of-flight mass spectrometer (TOFMS) has been successfully developed and applied to direct and on-line analysis of smoke generated during combustion. The mass spectra of smoke were obtained in conjunction with the effects of gas species (air, Ar and He), pressure (1600-2600 Pa) and current (10-130 mA) of the SPI discharge. To investigate the ionization mechanism of the SPI, we also have studied spontaneous emission spectra from the SPI source. Considering the results from mass and emission s pectral data, we suppose an ionization mechanism of the SPI which can efficiently produce excitation ofN_2 in the presence o f the noble gas, leading to promote ionization of sample.
