ICP-OES

Quantifies elemental composition by exciting atoms in an extremely hot plasma and measuring the specific wavelengths of light each excited element emits as it relaxes back down.

References

• Greenfield, S., Jones, I.L., Berry, C.T. "High-Pressure Plasmas as Spectroscopic Emission Sources." Analyst 89, no. 1064 (1964): 713–720.