slowing down/stoping a particle system's speed -after timestep value

Hi.

I’ve searched this forum for answers regarding to slowing down or stopping a particle system -the “bullet time” effect-. In some threads, the solution I’ve found is keyframing (reducing) the timestep value, like Atom and Richard Marklew have pointed out; this works well but, when returning the timestep value back to normal, accumulated particles appear due to the fact that they are still being generated at the same rate.

Is there any solution other than using a particle node branch of Blender 2.62 from graphicall.org in order to successfully achieve this effect?

I appreciate any help, thanks.