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Magnetically confined laser-induced breakdown spectroscopy was investigated by studying the optical emission from laser-induced plasma plumes expanding across an external transverse magnetic field. KrF excimer laser pulses with a pulse duration of 23 ns and a wavelength of 248 nm were used to produce plasmas from Al, Cu, and Co targets. Various optical emission lines obtained from Al and Cu targets show an obvious enhancement in the intensity of optical emission when a magnetic field of ~0.8 T is applied, while the optical emission lines from Co targets show a decrease in the optical emission intensity. The enhancement factors of optical emission lines were measured to be around 2 for the Al and Mn (impurity) lines from Al targets, and 6–8 for Cu lines from Cu targets. Temporal evolution of the optical emission lines from the Al samples shows a maximum enhancement in emission intensity at time delays of 8–20 μs after the incident laser pulse, while from the Cu targets it shows a continuous enhancement at time delays of 3–20 μs after the pulse. The enhancement in the optical emission from the Al and Cu plasmas was presumably due to the increase in the effective plasma density as a result of magnetic confinement. The decrease in the emission intensity from the Co plasmas was suggested to be due to the decrease of effective plasma density as a result of the magnetic force.