Might have my math wrong
but this gave me the idea that if one was not to exceed 65 C (or 150 F), the approximate decarboxylation temperature for THCa, we could vaporize the compound by lowering the boiling point by decrease the atmospheric pressure.
This along with a few online Boiling Point Calculator
Theoretically, THC could vaporize below 65 C (150 F) at a pressure below 136 torr. If the physical properties of THCa have any resemblance or similarity to THC, one might observe the vaporization of THCa without decarboxylation occurring. And if this could occur, it would be interesting to see if the phase change(s) between solid and gaseous THCa are multi step (solid to liquid to gas) or straight sublimation.
Now after rechecking the math and reminiscing all of my distillation runs, I’m finding it hard to believe this would work. Under a full vac, I cannot recall seeing any significant vaporization occurring with the exception of solvents and volatiles.