Spectral Caracteristics of Balmer Series Lines in Dense Hydrogen Plasma Produced by a Linear z-Pinch Discharge

Abstract

The excited level population of hydrogen in dense plasma has been calculated by the collisional-radiative model. We took the ion density and the ground-state atom density as parameters, instead of assuming an ionization balance. We have found that, in the ionizing phase, the population density follows the distribution proportional to p-4.1 (p is the principal quantum number of the exited level.) In the recombining phase it is proportional to p2.3. The Balmer series spectrum corresoponding to these phases has been calculated, where the Stark line broadening and the continuum emissions were taken into account. It was found that these spectra differ substantially from each other. By using an optical multichannel analyzer, the Balmer series spectrum has been observed from a z-pinch plasma. The spectrum taken at the time of the maximum compression is consistent with the recombining plasma. On the basis of the above finding, we discuss the problem of the “transparency window” : a substantial reduction of the emission intensity near the series limit, which has been observed in dense plasmas. We conclude that our spectrum of the ionizing phase plasma could account for the apparent transparency window so far reported.