Wide-range measurement of non-impact excitation spectrum using ultrashort light pulses

The fluorescence measurement with ultra-short excitation pulses is made to determine the non-Lorentzian shape of the absorption probability in the very far-wing of the sodium D transition collisionally perturbed by rare gas atoms. The absorption probability has been determined in the detuning range from -400 to 1000 cm-1. A steep decrease of absorption probability in the far blue-wing has first been found. A simplified relation between this far-wing structure and the interatomic potential curves is given theoretically. The maximum of the difference potential between X2Σ and B2Σ, which are the unbound states of an exciplex consisting of sodium and rare gas atoms, is determined from our experimental results. (author)