You can find out with which collsion object you particle is colliding with the per particle attribute called "collisionGeometryIndex", which can be added from the general tab.

so you could do (assuming index 1 is what you are after, and you have lifespanPP on your particle):

if(particleshape1.collisionGeometryIndex == 1)
{
    vector $pos = particleshape1.position;
    particleshape1.lifespanPP = 0;
    emit -object particle2 -position $pos;
}

obviously the emit command needs some tweaking to get your desired result, but that should give you the idea.

By: Georg Kaltenbrunner [ Editor ]