Question Changing ParticleSystem attributes in script for future particles only

I'm trying to spawn particles with random angular velocity between 30 and 66, but in either direction. I could random between -66 and 66, but then of course I'd end up with some particles barely rotating at all. Instead I randomize between 30 and 66, and put this in Update:

Code (CSharp):

1. if (Random.value < .5) {
2.     var rol = particles.rotationOverLifetime;
3.     rol.z = new ParticleSystem.MinMaxCurve(-rol.z.constantMax, -rol.z.constantMin);
4. };

Works great, except this also changes the angular velocity of particles that have already been spawned, resulting in them jittering back and forth. Is there a way to "detach" spawned particles from the ParticleSystem's values so they only affect future particles?

I'd also happily hear about a smarter way to get this effect.

 

Isn't this just the initial rotation of each particle?
https://docs.unity3d.com/ScriptReference/ParticleSystem.MainModule-startRotation.html

For my particles, this is just 0 — I'm looking for angular velocity.

 

Aha! I think I understand: if I give half of my particles an initial 180 degree rotation about the X, their angular velocity will take them in the opposite direction. Works great, thanks.