Shock wave confinement-induced plume temperature increase in laser-induced breakdown spectroscopy

Spatial confinement is found effective in improving the sensitivity of laser-induced breakdown spectroscopy (LIBS). This work reports on the physics of shock wave spatial confinement via atomistic modeling. Reflection-induced atomic collision/friction near the wall reduces the shock wave velocity close to zero and remarkably increases the local temperature (∼218 K) and pressure. As a result, the reflected ambient gas expands quickly toward the plume and compresses it. The temperature of the plume goes up significantly in the compression process: from 89 to 132 K. The lifetime of the plume is also boosted dramatically, from 480 ps to ∼1800 ps.