Empirical Formulae for Electron Density Diagnostics from Hα and Hβ Line Profiles

We present empirical formulae for the electron density vs. line profile widths and shifts developed from precise measurements of hydrogen Balmer series alpha and beta emissions for diagnostics of laser-induced plasma. The formulae are for the Stark width and Stark red shift of the Hα line, as well as for the Stark width and peak separation of the Hβ line and are tested using measurements of Hα and Hβ emissions in laser-induced plasma following ablation of an aluminum surface in a hydrogen gas atmosphere. The Hα and Hβ line widths and Hα line shift are determined by fitting the measured spectra with Voigt profiles. The Hβ peak separation is found by direct inspection. For example, the Hβ line shows Ne of 3.2±0.3×10 17 cm-3 and 3.8±0.5×1017 cm-3 from the line width and peak separation, respectively, at a time delay of 0.65 μs from plasma generation. PACS Codes: 52.38.Mf, 32.70.Jz, 33.70.Jg