Abstract
Intense vacuum-ultraviolet stimulated emission in molecular hydrogen, on both the Lyman and Werner bands, following excitation by two-quantum absorption at 193 nm on the , transition, has been observed. The shortest wavelength seen in the stimulated-emission spectrum was 117.6 nm corresponding to the transition. The state appears to be populated with a mechanism involving electron collisions. The radiative cascade mechanism found to lead to the vacuum-ultraviolet emissions on the Lyman band also causes strong infrared stimulated emission to occur on the , band. Two entirely separate radiative excitation channels are observed to play important roles in the state-selective molecular population of the , level. One involves two 193-nm quanta in the , amplitude while the other process combines a 193-nm quantum with a first Stokes-shifted photon in . The optical Stark effect was seen to play a significant role in the excitation process with shifts of molecular resonances as large as ∼45 . Substantial deviations from Born-Oppenheimer behavior, resulting in a dramatic shift of the stimulated spectrum depending upon the excited-state rotational quantum number, were clearly observed for molecular levels close to the potential maximum separating the inner and outer wells of the , state. The maximum energy observed in the strongest stimulated line was ∼ 100 μJ, a value corresponding to an energy conversion efficiency of ∼ 0.5%. The pulse duration of the stimulated emission is estimated from collisional data to be ∼ 10 ps, a figure indicating a maximum converted vacuum-ultraviolet power of ∼ 10 MW.
- Received 21 March 1983
DOI:https://doi.org/10.1103/PhysRevA.28.795
©1983 American Physical Society
