Study of collisional redistribution using two-photon absorption with a nearly-resonant intermediate state

The authors report studies of collision-induced features of the 3S1/2→3P1/2→4D3/2 two-photon absorption in atomic-sodium vapor undergoing collisions with several rare-gas perturbers. The results yield the collisional redistribution function which describes the nonresonant excitation of the 3P1/2 intermediate state. Good agreement with theory is obtained only if effects of 3P1/2↔3P3/2 state-changing collisions are included in the calculations. Results are used to obtain a value for a pressure-broadening coefficient in the Na-Kr system.