Using coroutines to pause the game

I’m trying to make a particlesystem appear upon a collision and make it disappear after three seconds. Can I accomplish this using coroutines? The code I have so far (which doesn’t work) is:
using UnityEngine;
using System.Collections;

public class NewBehaviourScript : MonoBehaviour {
public ParticleSystem ps;
private float amt = 3f;

// Use this for initialization
void Start () {
ps.renderer.enabled = false;

// Update is called once per frame
void Update () {


void OnTriggerEnter (Collider other) {
	ps.transform.position= new        Vector3(this.transform.position.x,this.transform.position.y, this.transform.position.z);
	ps.renderer.enabled = true;

IEnumerator pauser()
	yield return new WaitForSeconds(amt);	

In your trigger function, you destroy the object first, so anything coming after won’t do.