Balmer series H_β measurements in a laser-induced hydrogen plasma

Abstract

Stark-broadened emission profiles of the Balmer series Hbeta lines are measured subsequent to nanosecond laser-induced optical breakdown in gaseous hydrogen. Electron number densities are found from time-resolved spectra from Hbeta emissions to be in the range 10(15)-10(18) cm(-3). These results are compared with Halpha measurements for which number densities as high as 10(19) cm(-3) are determined from Stark widths and Stark shifts. Good agreement is reported for number densities inferred from Halpha and Hbeta emissions, down to an electron number density 3 x 10(16) cm(-3), by accurate treatment of ion dynamics in the theory.

Measurement of Electron Density from Stark-Broadened Spectral Lines Appearing in Silver Nanomaterial Plasma

“…In general, the laser produced plasma is inhomogeneous even though the laser device operates in the lowest order transverse electromagnetic mode, i.e., TEM 00 [1][2][3][4][5][6][7][8][9][10]. Actually, there are two regions in the plasma produced by laser radiation.…”

“…Theoretical calculations of Stark broadening parameters of hydrogen and hydrogenic lines are communicated by H. Griem [4] and E. Oks [9][10][11]. Precise fitting of the measured line shapes to convolutions of Lorentzian and Gaussian spectral line shapes (i.e., Voigt line shapes) allows one to extract the Stark full width at half maximum (FWHM).…”

New Source of the Red Shift of Highly-Excited Hydrogenic Spectral Lines in Astrophysical and Laboratory Plasmas

“…The largest standard contribution is due to quenching, i.e., non-zero Δn (Griem [14]) and elastic, i.e., zero Δn (Boercker and Iglesias [15]) collisions with plasma electronshereafter, the electronic shift (see also paper by Griem HR [16]). For high-n lines, the primary component of the electronic shift comes from the quenching collisions: it scales as ~ n 4 , while the secondary component (originating from the elastic collisions) scales as ~ n 2. Table 1 presents the electronic shift Se of the hydrogen SL H 13 -H 17 , calculated by formulas from papers by Griem [14,16], and their comparison with the shifts from paper by Bengtson and Chester [10] observed in astrophysical and laboratory plasmas.…”

“…Namely, after taking into account the quadrupole corrections not only to the energies/frequencies, but also to the intensities, and then summing up over all Stark components of a hydrogenic SL, the center of gravity shift vanishes at any fixed value of R or F 1 [18]. So, within the approach of the multipole expansion, the first non-vanishing ionic contribution to the shift of hydrogenic SL should come from the next term of the multipole expansion: from the term ~ 1/R 4 …”

“…In astrophysics, red shifts of SL are observed in various astrophysical objects: for deducing the relativistic (cosmological and gravitational) red shifts (see, e.g., book by Nussbaumer and Bieri [3]) from observed red shifts it is necessary to take into account the Stark shift. In laboratory plasma diagnostics, measurements of the Stark shift can complement measurements of the Stark width for determining the electron density -see, e.g., paper by Parigger et al [4].…”