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Optical Emission Spectra from Laser Ablation of Graphite at 266 nm and 1064 nm under a Magnetic Field

Optical emission spectra were measured during laser ablation of graphite at 266 nm and 1064 nm at fluences of 1.7–12.2 J/cm2 with or without a magnetic field of ∼0.1 T. In the presence of magnetic field, the intensity distribution of C, C+, and C2+ emission lines varied considerably and some of the emission lines which originated from higher excited states became obscure. In addition, the C2 Swan band emission appeared, particularly during 1064 nm laser ablation. These changes in emission spectra are explained in terms of the 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 a magnetic field. We will discuss the formation and excitation of C2 and C2+, and deexcitation of electronically excited C+ and C2+.