Observation of Two-Photon Excitation of theH2E,FΣg+1State

Selective excitation of the $E$, $F{}_{}{}^1{}_{}{}^{}{\Sigma }_{\mathrm{g}}_{}^{+}{}_{}{}^{}$ state of ${\mathrm{H}}_2$ by two-photon absorption at 193 nm is reported. The excited population is detected by observing fluorescence arising from $E$, ${}_{}{}^1{}_{}{}^{}{\Sigma }_{\mathrm{g}}_{}^{+}{}_{}{}^{}\to B{}_{}{}^1{}_{}{}^{}{\Sigma }_{\mathrm{u}}_{}^{+}{}_{}{}^{}$ transitions. Experimental determinations of the radiative lifetime of the $E$, $F$ level as 100 ± 20 ns and collisional quenching rates for ${\mathrm{H}}_2$ and He as (2.1 ± 0.4) × ${10}^{-9\mathrm{}}$ and (0.8 ± 0.4) × ${10}^{-9\mathrm{}}$ ${\mathrm{cm}}^3$/sec, respectively, have been made. These experiments involve the first selective population of an electronically excited gerade state of ${\mathrm{H}}_2$.