First of all phasers do not need to be a chain reaction. Note that, for example, water boils at room temperature if pressure is low. All what you need are exotic particles that transfer energy from phaser and turn it into transition (= vaporization) energy without heating energy. I like this idea,But even this is problematic because weapon A could have another effect on target 1 than on target 2, on which weapon B was used, which could have another effect on target 1. That applies especially on weapons, which induce a chain reaction in its target. In another target, it would maybe not be able to induce such a chain reaction although the target would be far easier to destroy by an direct energy transfer while the other target is easier to destroy by inducing a chain reaction.
In such a case, the figures of the equivalent amount of energy, a "classical" weapon would need for such a task, wouldn't be usefull.
and also that phasers inertate atoms.
Second, if there is a chain reaction which works on elementar
(baryonic) particle level, than, as ALL matter consists of baryons, the DET equivalent of the shot would be pretty much the same in all targets. So if a target is harder to destroy, its because it neds bigger DET equivalent.