Asymmetric hydrogen beta electron density diagnostics of laser-induced plasma

The hydrogen beta line has been widely used in determining plasma parameters such as electron density. In conjunction with other Balmer series lines, electron temperature can be inferred. The asymmetric appearance of the hydrogen beta line, due to quadrupole interactions, can be utilized as well for the determination of electron density. Laser-induced optical breakdown is generated in laboratory air, and particularly for electron densities in the range of 0.3 to 1.0 × 10¹⁷ cm⁻³ the use of the asymmetry parameter is elaborated for electron density diagnostics. Also included are results of analysis of the hydrogen beta profiles for which the asymmetry indicates an electron density on the order of 2.0 × 10¹⁸ cm⁻³, which is significantly higher than 6.3 to 6.8 × 10¹⁷ cm⁻³ maximum that was measured previously from the Stark-broadened hydrogen beta width following laser-induced optical breakdown. - Highlights: • We present LIBS results of laboratory air plasma. • This includes measurement of electron density. • We evaluate hydrogen beta asymmetry for electron density diagnostic. • Use of the FWHM for electron density is preferred