Two-photon optical free induction decay measurement by broad-band excitation in undirectional beams

Measurement of two-photon linewidths by broad-band excitation is reported, for the first time in unidirectionally propagating beams. Free induction decay measurement is used in order to determine the pressure broadening coefficients for the 3s–5s transition of Na for collisions with He and Ne. At high He, Ne concentration the Doppler effect and the collisions of other types of atoms are eliminated.