How do I set the width of a particle system using code in Unity 2D? (C#)

 using UnityEngine;
 using System.Collections;
 
 public class ParticleSystemFitter : MonoBehaviour
 {
     void Start ()
     {
         ParticleSystem pSystem = GetComponent<ParticleSystem>();
 
         //Just checking if everything's OK
         #region checks
         if(pSystem == null)
         {
             Debug.LogError(name + " is missing Particle System!");
             return;
         }
 
         Camera camera = Camera.main;
 
         if(!camera.orthographic)
         {
             Debug.LogError("Camera is not in orthographic mode!");
             return;
         }
 
         if(pSystem.shape.shapeType != ParticleSystemShapeType.Box)
         {
             Debug.LogError("Particle system is not in a box shape!");
             return;
         }
         #endregion
 
         //calculating camera's viewport ratio
         //if you don't cast those ints to floats, you'l get a bit different result 'cause int's division is different
         float ratio = (float)camera.pixelWidth / (float)camera.pixelHeight;
 
         //calculating particle box based on camera's orthorgaphic size (which is in world space)
         //and camera's veiwport ratio;
         //multiplying by 2 'cause orthorgaphic size is the half of camer's viewport height
         Vector3 particleBox = new Vector3(2f * ratio * camera.orthographicSize, 2f * camera.orthographicSize, 1f);
 
         //applying this box to the particle system
         ParticleSystem.ShapeModule shape = pSystem.shape;
         shape.box = particleBox;
     }
 }

Any questions?