The influence of the optical stark shift on the two-photon excitation of the molecular hydrogen E, F1Σ+gstate

The first demonstration of the use of the optical Stark effect to secure resonance for a two-quantum process in the ultraviolet is reported. Following excitation of molecular hydrogen by 193 nm radiation, intense stimulated emission on both the Lyman and Werner bands is observed. The Werner (2-5)
Q(1)
transition at 117.5 nm exhibits a conversion efficiency of ∼0.2 percent. It is found that electron collisions with excited molecules provide the most probable mechanism for excitation of the
C^{1}\Pi_{u}
levels with a rate constant estimated to be
k_{e} \sim 7 \times 10^{-6}
cm
³
/s.