Analysis of the visible emission from optical-field–ionized hydrogen
Max-Planck-Institut für Quantenoptik - D-85748 Garching, Germany
2 Foundation for Research and Technology-Hellas - Crete, Greece
Accepted: 22 October 1999
Visible emission from an optical-field–ionized hydrogen plasma is investigated and analyzed. Molecular hydrogen at pressures from 5 to 20 mbar is subjected to 200 fs laser pulses at a peak intensity of . Time-integrated spectroscopy reveals that the emission consists solely of hydrogen Balmer lines. A fast streak camera is used to record the time-resolved emission of the Balmer-alpha (-) line with a resolution of 15 ps. This shows a slow part, which is due to recombination from bare nuclei into excited hydrogenic states, and “prompt” emission, which is interpreted as being due to rapid adjustment of excited hydrogenic levels into local thermodynamic equilibrium (LTE) with the bare nuclei. This interpretation of the observed emission is supported by simulations of the plasma with a collisonal radiative code.
PACS: 32.30.Rj – X-ray spectra / 42.65.Re – Ultrafast processes; optical pulse generation and pulse compression
© EDP Sciences, 2000