How to create a smooth animation with particles

[Drosaca]

I would like to decrease the speed of particles until complete stop but when i tried it by using a state on the input options the result i got looks more to a shaking effect than slowing down, is there a conventional way of doing it ?
thanks

[matteobruni]

Use particles.move.decay option, sample here: https://codepen.io/matteobruni/pen/RwmMbWq