Abstract
Optical emission spectroscopic studies were carried out on ablation plumes produced by laser ablation of graphite at 266nm and 1064nm in vacuum and in nitrogen gas atmosphere with or without a magnetic field of -0.1 T. In vacuum, in the presence of the magnetic field, the intensity distribution of C, C+, and C2+ emission lines were varied remarkably and some of the emission lines originated from relatively higher excited states became obscure. In addition, C2 Swan band emission appeared particularly during 1064nm laser ablation. These changes in emission spectra are interpreted by promotion of ionization of C and C+, formation of C2, and deexcitation of electronically excited states, resulting from enhanced collisions between ablated species due to cyclotron motions under the magnetic field. In nitrogen gas atmosphere, enhanced N2 emission (2nd positive system) was observed and explained by electron-impact excitation of N2 molecules.
