Particle system detection

I'm a newby in Unity3d, and I dont know how to make a particle system collision. My player is shooting with a fireballs made of one particle and I need to make a damage to the enemy which has collided with the particle. I've read the manual, but I dont really understand it. I wrote a script, but it doesnt work. Could anybody please explain how to make it work?

     void OnParticleCollision(GameObject other) {
             Rigidbody player = other.rigidbody;
             if (player) {
                 Debug .Log ("ff");
     }
 }