The Autler‐Townes effect (also known as ac, optical or dynamical Stark splitting) on the Balmer‐α transition of hydrogen in 0.5–5 torr of helium is investigated. In the double optical resonance scheme, H(3p) is excited by absorption of two 243‐nm photons and a 656‐nm photon via the 2s resonant intermediate level. Calculated results show that in a Doppler‐free or a ‘‘Doppler‐reduced’’ beam configuration, the required intensity of the 656 nm laser (0.2 cm−1bandwidth) for observing the Autler‐Townes doublet has to be greater than 2×104 W/cm2 and 2×105 W/cm2 for a 243‐nm laser bandwidth of 0.1 cm−1 and 0.5 cm−1, respectively.
The author investigates the Autler-Townes effect (also known as AC, optical or dynamical Stark splitting) on the Balmer- alpha transition of hydrogen in 0.5-5 Torr of helium. In the double optical resonance scheme. H(3p) is excited by absorption of two 243 nm photons and a 656 nm photon via the 2s resonant intermediate level. Calculated results show that in a Doppler-free or a 'Doppler-reduced' beam configuration, the required intensity of the 656 nm laser (0.2 cm -1 bandwidth) for observation of the Autler-Townes doublet has to be greater than 2*10 4 and 2*10 5 W cm -2 for 243 nm laser bandwidths of 0.1 and 0.5 cm -1 , respectively.
The author develops a theory of ac Stark (or Autler-Townes) splitting occurring in double optical resonances, one of which is a two-photon transition. It includes both laser bandwidth and collisional broadening effects. Theoretical results are in excellent agreement with Goldsmith's observation of two-peaked structures in the multiphoton excitation spectra of atomic hydrogen in atmospheric-pressure flames. This is believed to be the first study demonstrating that the peak asymmetry in an ac Stark doublet can be reversed due to pressure broadening.