We have measured the deflection of a thermal sodium beam by a force ex
isting in a field of two counterpropagating short laser pulses. This f
ield was created by a II-pulse train of a mode-locked (mode) (spacing
82 MHz) dye laser beam, perpendicularly crossing a thermal sodium beam
and retroreflected from a mirror behind it. Unlike the spontaneous fo
rce, this II-pulse force is not limited by saturation effects and does
not heat up the sodium beam transversally. Calculations yield a maxim
um II-pulse force about three times larger than the spontaneous force,
being in good agreement with our experimental results.