Preparation of atomic sodium as a two-level atom

P. Thomann

The fluorescent intensity of two-level atoms irradiated by a near-resonant amplitude-modulated light wave is calculated in the Bloch model. The analogy with magnetic resonance in a strong oscillating field making an arbitrary angle with the static field is pointed out. Experimental evidence of the predicted parametric and multiple quantum resonances has been obtained with an atomic beam of sodium. Optical pumping was used to prepare the sodium atoms as two-level systems.

W. Bruce Hawkins

M. L. Citron, H. R. Gray, Conger Wren Gabel +1 more

Two frequency-stabilized cw dye lasers and an atomic beam were used to prepare sodium atoms in the aligned $F=2$, ${M}_{F}=2$ ground state, and to study power broadening in the transition from this ground state to the $3{P}_{\frac{3}{2}}$ $F=3$, ${M}_{F}=3$ excited state. This system is, to extremely good accuracy, a two-level atom. The line shape was determined as a function of the incident field strength and found to be accurately a Lorentzian over a large range of incident field strengths. The power broadening and saturation at resonance of the two-level system also agree with theory.

W. Bruce Hawkins, Robert Henry Dicke

F. Biraben, K. Béroff

E. Krüger

The steady-state absorption of a beam of sodium atoms irradiated by a train of pulses from a mode-locked dye laser has been measured. The sodium atoms were prepared as two-level systems by optical pumping with a two-mode laser. Absorption spectra on the 589.0-nm D2 line were recorded over 20 GHz with a frequency-stabilized, tunable, mode-locked dye laser having a bandwidth of 3.7 GHz and a mode spacing of 82 MHz. The laser-pulse profile was determined from the spectral profile assuming transform-limited pulses and was incorporated in theoretical calculations of excitation spectra obtained by numerical integration of the optical Bloch equations. By comparison of measured absorption spectra and theoretical excitation spectra the validity of the weak-field solution as well as the predicted saturation behavior were fully verified by the experimental results. For the highest level of irradiation applied, the laser pulses were identified as π pulses.